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Tuberific Q&A from Bob Carver's eBay auctions
TNRabbitOffline
#1 Posted: Wednesday, August 12, 2009 3:27:39 AM(UTC)
 
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I didn't have time to search but found this transcript of the Q&A from one of Bob's Tube Amp auctions on ebay & wanted to get it down for posterity before it is lost forever (If you look closely, Bob published his Sunfire email address in here!):

"Q: Hi Bob, redstone7 here again from Colorado Springs, I have to ask one more question......is there ever going to be a tube preamplifier offered from your camp right here on E-Bay??? Thanks much, Rob Mar-21-09

A: Hi Rob'stone7, not from me ( I should never say never), but James Sauter IS planning to build an exact copy of the preamp I designed for the Silver Sevens long ago. He may be found on the Carver Fest forum. Thanks again, Bob Carver

Q: continued,, so now there is being fed to the bias pot a filtered neg. DC, that is decoupled from the filter capacitors, that can change with without the lag that a capacitor would cause. It must have been pretty darn fast because I could hook the amp to a scope,set idle to 15ma. suddenly zap a sinewave to it big enough to drive right up to just before clipping, and the sine wave would instantly appear with out gradually climbing up with flattened tops. That was good enough for me!!!!! I have bailed out of tube equipment, am now making chip amps from the latest audio grade offering from National Semiconductor.. they sound very "tubelike" to me (and many others) Just in time because I am getting too old to manhandle heavy iron. nevertheless I still maintain a keen interest in new ideas in tube technology. I would love to see a schematic of these amps..could you send me one to my email? The 6al5 is a high perveance duo diode.I'm trying to imagine how it is implemented..Neal Mar-21-09

A: Hi Neal, I would be happy to send you a schematic....just e-mail me after the auction to remaind me. Don't forget to include your e-mail! Bob

Q: Greetings Bob, I have followed you since the Silver 7, and Tim since the EAR, and I can not think of any other two who have added so much good music to the world. In fact reading of the Silver 7 is what got me interested in tubes...again (built my first tube amp in '57 with bits and pieces of discards, but cost drove me to transistors in 65 and cheap speakers masked the difference). Might it be possible for you to come up with a "kit" or built bias 'controller' that would be adaptable to different amps. I have a Meas Baron tri-tube modified which I love, but 1 bias and 1 balance pot to control 6 tubes per side requires frequent tweeking even though I use current matched tubes. It seems there is much interest in a better bias method. I have seen this in questions for the amps you have offered, and in many of the DYI groups as well. Many not be exciting to do, but it is a much needed product, and important tweek for tube amps. I you'd be swamped with sales too cordially, bud Mar-21-09

A: Hi 'greg, I too have a pair of vintage Mesa Barons with six 6L6's per mono block amp. Beautiful amps! The 6AL5 DC restorer is the answer to your problem, plus it will stop the DC bounce that inevitably creeps into the system as the grid bias "hunts" under dynamic conditions. E-mail me after the auction and I'll send you the complete fix and the schematic as I used in my Baron. Warmest and best, Bob Carver

Q: Hi Bob...thank you for responding to my confusion concerning your bias scheme,,but first I want to say to the bidders:....BID AWAY, BOYS AND GIRLS.I HAVE INDEPENDENTLY DUPLICATED THE ESSENTAL FEATURES AND CAN ASSURE YOU THIS IS THE ONLY WAY TO OPTIMIZE FOR AUDIO QUALITY AND LONGEVITY. SO BID WITH ASSURANCE MORTGAGE YOUR HOME IF YOU CAN GET ONE OR EVEN HAVE A JOB LEFT TO THINK ABOUT IT Ok I think I know where my confusion lies----when I say sliding bias I mean changing the G1 negative voltage....when you say sliding bias you refer to a particular TECHNIQUE to change G1 neg. volt. Consider the neg source half or full wave, there will be a smoothing cap followed by a an RC tage ,followe by maybe another RC smoothing stage..Now follow with a resistor voltage divider WITH NO CAPACITOR ..the center connection now feeds the bias pot..One leg of the volt divider is paralleled with a device that changes resistance with input drive....continued Mar-21-09

A: Not exactly, but close enough for Gov'nt work. Keep that brain going 1000 RPM and we can have a scientific discussion about bias off-line. Bob

Q: dear Bob....thank you for hanging in there with my audio-amatuer forays into mysteries of tube amps. I don't understand your bias stablization...it doesn't jive with your comments which I quote here "the dc restorer eliminated the need to idle each output tube at 50 watts yielding instead an idle power of 12 watts per tube....It works by keeping the dc componant on each output tube grid the exact value throgh the entire audio signal swing allowing perfect performance up to and even beyond clipping" Well, if by dc componant you refer to the negative bias grid voltage this is exactly how I describe my sliding bias scheme. If your bias scheme doen't shift the negative bias as the amp moves away from idle it will soon run into class B operation and really gross distortion. Your previous response says the bias doesn't slide , but if by slide we mean changing the bias voltage , then it MUST slide to my way of thinking...I'm confused cordially neal Mar-21-09

A: Hi '541, ....It jives perfectly with my comments. A sliding bias scheme has too much delay in responding under dynamic conditions OR it has too much control voltage ripple modulation for my taste. Such a scheme must ALWAYS be a compromise between the two. That's because it will have a detector diode, an integrating capacitor, and a time constant comprised of the final smoothing RC filter. The topology is often similar to a meter drive circuit. On the other hand, a DC restorer operates such that the DC value of the waveform on the grid remains where we want it even in the presence of asymmetrical, haversine signals. And its delay time is essentially zero because there is no filter capacitor to charge and therefore no time constant. Works far better, and is far more elegant than a simple and coarse sliding bias circuit. Bob Carver

Q: Bob....Come on..Bob..don't you want to explain to the prospective buyers the magic trick of 12 watts idle ( 18ma. at 660 volts anode) per output tube and not slide the bias to lower and lower negative G1 volts under progressively greater dynamic conditions to keep out of class B operation and unlistenable distortion?? ("My dc restorer is not a sliding bias approach, rather its purpose is to keep the DC value on the control grid at design center etc etc" your words , not mine) we are all waiting with breathless anticipation cordially Neal in Oregon Mar-21-09

A: Continued next following.

Q: Hi Bob, can you say a bit more about how this amp sounds? Can you elaborate on "the sound: This amplifier stands with a small handful of the world's great vacuum tube amplifiers" a bit more, especially sound-wise, which of the great amplifiers are most similar to your amp? Thank you, Frank Mar-21-09

A: Hi '211k, I would say my own Silver Seven's, my Subsequent Silver Sevens with extra output tubes and dual screen regulators. (Two 6550's per amp.) The $30,000 Manley amps, and the Mesa Barons at 150 watts. I've limited this to vintage amps. Hope it helps, Bob Carver

Q: ...which output tubes are used in this amp, 6550's or the kt88's, the write up refers to both articles tim depravacini/stu hegeman and yourself, is there any difference between the carver/pravacini mono's and carver/hegeman mono amps? thank you! david Mar-21-09

A: Hey old friend, these amps use KT88's. The difference is in the front end; these use 12AT7's, 12AX7's, and 6AL5's with KT88's. The Hegeman units use 6AW8's, 12BH7's, and 6AL5's with 6550's. I cannot answer the question which one do I like better because it's just like asking which of your children do you love more. I love them both the same, even though they each possess distinctive audio personalities! Bob Carver

Q: What an honour to be able to ask you a question,Bob. How do you think these amps would match up with Apogee Duetta Signatures' current and voltage loads, and would you recommend running both MT ribbons and bass panels with them ? (Trying to get away from present biamping with chip amps on bass and tube hybrids on MT ribbon and into a more coherent one-amp sound, if that makes sense). Your vintage pair here have come up on the Apogee users' website as one possible ultimate amp for Apogees, which would be wonderful for one who, like me, is just looking for that final and permanent piece of his system. Mar-21-09

A: Hi 'fitte, I prefer the one-amp coherent sound unless the amplifier is not powerful enough to avoid clipping and overload on some of your music. This amp has been designed to run the Apogee Scintilla one ohm speaker....I really worked hard to get it to do that. So it should be a walk-in-the-park for the Duetta. The power increases as the impedance decreases....up to 300 watts, just what the Apogee needs and loves. I would not bi-amp here, perhaps bi-wire with heavy gauge for the bass panels and finer wire for the ribbons. Try it both ways. Bob Carver

Q: Hello Bob, I was reading your writings here and you mentioned that your friend Stu liked the 6550's better than the KT-88's but I see you opted for the 88's on this design,is there a specific reason because of the overall design or is it more about personal preference? The funding is not here to bid on your current effort but I'm right in the middle of re-tubing my MC-275's and your input would be greatly appreciated , Thanks, Rob McRae in Colorado Springs Mar-20-09

A: Hi 'stone 7, Remember that Stu was designing tube amps long ago and the KT88 was very new on our shores. At the time, the mighty 6550 was supreme, was considered the best and the finest, and was used by all the great designers back then. However, the KT88 was on its way. I love both tubes and would be happy with either, but I have a giant stash of NOS vintage KT88's to use from my museum. Bob

Q: Hello Mr. Carver, is there any comparison between these beauties and the legendary Silver series of tube amps you created long ago ?? Could they realistically be produced again, given the growing high-end audio gear market, especially in the tube sector ? Since I was unable to attend CarverFest last year, I'm still hoping to view the Q&A session that was recorded , I submitted questions for you and have yet to learn what your answers were ! Maybe this year !!! Respectfully yours, silver7t1 Mar-20-09

A: Hi '7t1, Oh no! I never got your questions, or perhaps I did and have forgotten. Try again at bob.sunfire@gmail.com., The relationship between the two amplifier designs is what I call crystalized knowledge. The Silver Sevens are similalar to the 520 circuit, whereas these have the cicuit described above. You bet this year! Bob Carver

Q: Hello Bob I consider it a honor to even ASK you a question, let alone receive an answer!LOL Anyways I'm wondering about the transformers, can you disclose what they are for primary Z? Also I don't see a choke in your PSU, is it CRC filtered then? Thanks WOT Mar-20-09

A: Hi 'tour, I have hooked them up to match four output tubes, so in this design, since I have six of them they are intentionally underloaded which allows them to operate such that an easy 180 watts is obtained, and is the reason the output power can increase when havily loaded with a difficult to drive speaker load. All CRC filtering, and with so much that a vintage designer woul find it difficult to believe.

Q: Bob - Oops, forgot that the text mentioned the bias control. I am fascinated by the driver. It looks like a 12AX7 sized T-6 tube, short envelope. I would be interested in finding out what it is. Again, it looks like a 5687. Tim Smith Mar-19-09

A: It's a 12AT7 double mica, military frame grid NOS tube and can easily drive three outputs per plate with a 33,000 ohm resistor following. See the RCA tube manual. Excellent question. Bob

Q: Bob- Will you ever decide to release this tube amp design for production commercially? Mar-19-09

A: Hi '1, I would love to but that would take more vintage parts than I have to spare. I don't know what I'll do when I run out of output transformers, but I'll think of somthing....maybe I'll just clone a Partridge or something, as I still have my old transformer winding machine.Warmest and best, Bob Carver

Q: Hey Bob---just let 'rama know he can find me by going to my eBay page. He can go to the site map, click on find members, and put in tubular_joe. Thanks! Mar-19-09

A: Got it! Bob

Q: Bob - Magnificent amps! A few questions but don't the feel the need to answer if you'd be compromising proprietary information. It looks like the KT88 grids are fed from the 6AL5 cathodes - can't tell, the chassis photo is grainy. Also, are all of the KT88s controlled by a single bias pot (rear of amp?) or does your circuitry handle bias needs - can't tell if there's a bias pot at the rear. Is the driver tube a 5687? That strikes as about the only small tube (non-Russian) that would have the ability to drive a sextet of KT88s. I've built amps for several years, essentially all with regulated pentode output stages; think they sound the best. I recently finished a 45 watt/channel rig that uses Russian 6P41S vertical amp tubes run at 460 on the plates and 185 on the screens, If you're interested I can send photos; email address is ***edited***. Good luck selling these, I hope they find a good home. Thanks, Tim Smith Mar-19-09

A: This is going to be a fast answer...I'm on a two minute time-out computer. The drive comes from a 12AT7. The 6AL5 IS connected to the grids to control the D.C. All the output tubes are cintrolled by a single pot, not for balance so much as for the ability to trim the soundstage envelopment. And yes I would love to see see photoes.

Q: It is a pleasure and a privilege to view your tube amp and to read your Q&A. You are truly a designer for the people, reminiscent of when you took the Stereophile challenge and made affordable gear sound like reference. Sorry for the off topic question but I am dying to know if there is a postscript to the challenge. Cheers! Mar-19-09

A: Hi 'it, Well, the only postscript that comes to mind is that after all these years, the original article is still being posted around the world in several languages and many forums. It suprises me to this day that a single article by J. Gordon Holt has had so much staying power. Thank you for writing, Bob Carver

Q: Dear Bob, Another thought I have is concerning your comment that only four types of circiut designs for tube amps have ever been invented. With your design being a 5th circuit, would it have been possible to design this circuit 50 years ago with the type of componets available at the time or would you have had to add a bunch more tubes and circuits to accomplish the same design 50 years ago. Am I making any sense? Thank you again, Frank E. Mar-19-09

A: Hi Frank, What a great question. sinc`e this amp is built of vintage parts, it would absolutely have been possible 50 years ago. Even the 6AL5 was around back then. But neither Tim nor I were. And yes, you make a lot of sense! Bob Carver

Q: Dear Bob, I have a quick question, for my own information. I like the look of your pots. Are they a pot and or transformer combo that you made. My only guess is maybe McIntosh?? And if your quad wiring and DC Restorer are available to look at on a schematic. ( if your pats. are secure and filed of course). I am not going to copy it at all, just interested, of course! Thanks again, Frank E. Mar-19-09

A: Hi '632, I don't remember where I got the pots....it was so long ago. Remember, I was old when Atlantas sank! I'll send you a schematic if you remind me after the auction, and you are welcome to copy it to build an amp if you wish. Thanks for writing, Bob Carver

Q: Hi Bob How many dB of Global Feedback do you use in these amps? Is the feedback on the secondary of the OPT? Mar-19-09

A: Hi 'Plies, Our amp uses the classical amount of 20 dB and if the output transformer is good enough to support a full twenty dB a switch on the front can change it to 11 db, a contemporary amount often used by modern amplifier designers. I prefer 20 dB. I prefer the full twenty if the output transformer is good enough to support it."
Rest in Peace Gary. Thank you for all the laughs.

May 19, 1961 - October 22, 2015.


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weitrhinoOffline
#2 Posted: Saturday, August 15, 2009 9:14:34 AM(UTC)
 
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I captured Q&A from the other Bob Carver tube amp auctions:
 
Question & Answer Answered On
Q:  Dear Bob, So good of you to stand with your amp and talk with all the tube lovers. When all is said and done its all about the community, the designs and the friendships. I have a review project that may make you smile. The 700 series 1. Its a wonderful amplifier and its magic still holds fast after all these years. I share your belief that there are only a handful of basic circuits but many offshoot iterations of them. I like the old 6bq5 integrateds from Heathkit/dyna/Stromberg...etc. To the point: I've been planning this vintage review of your 700 series 1 for Stereophile and to write an interview standout "sidebar" into the piece. It would be great to chat--when you have a chance drop me an email. Sincerely, Peter Breuninger, Stereophile pbstereophile@aol.com Nov-12-08
A:  Hi Peter, You sure do bring back some great memories; I recently bought a 6BQ5 Stromberg Carlson tube amp taken from an old console designed in the 1950's. It doesn't work, but I plan to fix it up and put it in my audio museum. I can't wait to read your review of my first Phase 700. Thanks for tripping me down Memory Lane, Bob Carver.
Q:  Hi Would you consider shipping this item to Canada? Thanks Art Nov-11-08
A:  Hi 'res, Art, I would be happy to ship these amps to Canada. I went to school at the UBC in Vancouver and spent some very happy time in your land of the blue water dolphin. Thanks for writing, Bob Carver
Q:  Bob, Just curious, why didn't you incorporate a triode option, since usually triode sound does have a very seductive transparent effect. I am using Strathern/EMIT/Magnepan ribbons on my QRS Infinitys and the triode sound makes them sound very unique. Nov-10-08
A:  Hi 'ster I did, as we shall see. Your question is deep, and my answer is as complex as your question is deep. So sit back, stay with me, and enjoy the intellectual and scientific journey. The triode sound owes it's particular characteristic to the fact that when an output tube is connected as a triode, the source impedance of the power amp drops to a very low value - often below 0.50 ohms. That's pure theory, but I happen to own a vintage Soundcraftman 500, pure Williamson, triode connected output section designed by Sid Smith of Marantz 8B and Model Nine fame. I measured it and found confirmation with theory, as well as with it's published specifications. Measured exactly 0.380 ohms. It DID sound different from the pentode sound, but that "seductive transparent effect" depended critically on the loudspeaker. On most of my speakers, including my new Cinema Ribbons and my friend's QRS's, the sound was just stunning with my amps. That's because the DC restorer allows the source impedance of the amp to be adjusted by the rear panel bias control. Sid's 500 sounded great too, but not greater, and of course it only delivered about 23 watts. When an output tube is configured for triode operation, it wastes about 60% of its available power supply voltage due to the fact it cannot pull its plate voltage to ground well. In addition, the plate voltage must be reduced in value to match the maximum permissible screen voltage, further reducing the output power. Bad news all around if you like power. With my amp, The DC restorer, in combination with the bias current adjustment range, allows a very low source resistance(approximately 0.30 ohms for the triode sound),AND more than 180 watts. Most tube amps have a recommended OPTIMUM bias setting for output tube idle current; my amp has a RANGE of recommended idle currents, allowing the sound to be controlled from triode sound to regulated screen(classic tube)sound - my favorite by far most of the time. Great question, Bob Carver
Q:  Hi Mr Carver would you take a money order from me if I win.Thanks Bert. Nov-10-08
A:  Hi '63 Bert, I would be happy to take a money order from you. And if you live close by, I will deliver the amps myself and help set them up with your speakers. Thanks for asking, Bob Carver.
Q:  Bob, Are you the same Bob Carver I met at the Jockey Club Hotel around '75 at the Vegas CES of that year? You had a lot to say then about building amps that would show how an inexpensive design could produce the same quality of sound as the most expensive amps, if it were done using old ideas presented in a new way. Well, it seems that history has proven you did that quite well. This looks like a new version of your old song. Only this time you are using the best of old ideas, old equipment, and old friends to create a new expression of the audio ideals I heard from you 30+ years ago. The question is, why are you selling this one of a kind creation? And, are you planning to go further with this design idea? Will it be a progenitor and standard of a new line of equipment like the Silver Sevens? Or, will this amp stand as a one-off with never another in the audio world to match it? Thanks for your good works over the years, PK Nov-10-08
A:  Hi 'PK, It is I, the very same Bob Carver. When we met at the Las Vegas Jockey Club so long ago, I was introducing my Sonic Hologram, the year was '79 0r '80, and I was just starting my Carver Corp. days. Wow! What a memory you have! As far as going further with this design, I have no intentions, none at all, of building these amps with parts other than from my museum. But I'm not out of parts from my vintage stash yet, so I'm pretty sure I'll be able to build at least one more pair. Thanks for the happy sentiments and deep questions, Bob Carver.
Q:  Dear Mr. Carver, I am very excited to see a pair of amplifiers designed by yourself and Tim De Paravicini. Unfortunately, I am unlikely to be able to afford to purchase them. I do build tube amplifiers for myself, once in awhile, and was wondering if you would be willing to make the schematic available. I'm not enough of an electrical engineer to design amplifiers for myself, and there's not, as you note in your advertisement, a lot of new and interesting designs out there. So it would be very exciting to put together a pair of these amplifiers. Thank you in advance for your response. Ben Nov-10-08
A:  Hi 'fm Ben, I will be happy to make a schematic available to you. The big problem will be finding output transformers good enough for the job. The second problem, though not so tough would be the big power transformer. Let me think about it and I'll try to steer you towards some suitable units. I would sell you a pair of my output transformers but I love them too much to do that. They are pretty special. I've had them since I was in college, and I think I loved them more than my girlfriend. Please contact me after the auction and after I've have had a chance to look around for something that will work okay. You are one courageous man! Good luck, warmest and best regards, Bob Carver
Q:  will you be selling anymore of these in the future, or is this the only set? Im a 22 year old in love with the sound of tube amps and looking for something amazing to add to my collection and listen to. James Nov-10-08
A:  Hi '515, I still have some of my vintage parts left, which I have "stolen" from my audio museum to build these amps. So my answer is I don't really know for sure, but probably will build at least one more set. Since you're 22 years old, I'm extra glad these amps will probably last over 50 years. I love tube amps too! Thanks for writing. Bob Carver
Q:  Does your amp use negative feedback and is it a class a design? Thanks, Jason 574 329-1850 Nov-10-08
A:  Hi 'walker, Yes, this amplifier uses negative feedback; it has a switch on the front panel to choose between classical amounts (20 dB) and contemporary amounts(9 db). Because of the DC restorer circuit, it operates in class A up to about 80 watts, then hands off to class AB for the rest of the way up to its maximum output. Great question. One last thing: This is the fourth pair of these amps that we have put up here on eBay, and during the last auction, I made several commitments to many folks who asked questions. Shortly thereafter my computer was completely scrubbed and I lost all of it! Soooo, if you are one of those folks, please contact me once again and let me know what it was I promised you and this time I will make sure I follow through. I apologize, I have no excuse, only that reason. Bob Carver

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#3 Posted: Saturday, August 15, 2009 9:20:02 AM(UTC)
 
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Question & Answer Answered On
Q:  Dear Sir, I am the guy everyone asks to fix things for them. I have tweeked my SS amp as far as it can go and would love to challenge myself with a new construct project like your amps. Living in detroit I find Vintage equipment at hand. So the problem of finding output transformers would be less for me. And I would like to think that they would make a nice match to the pair of Electro Voice Regency speakers I cherish so much. The full upgrade vesion with the T350's, T25's, and SP15's. All 8 Ohm with a crossover made by BEC. Who sells here and can be found on a few of the forums.If I can be included in the Schematics send off I would be honared. repair-tech@charter.net Nov-19-08
A:  Hi 'mp, Wow! I'm finding it difficult to believe how many souls want to build this amp. I almost built a Patrician for a friend last summer- T350, T25, SP12 and two 315's per cabinet, but decided to wait 'till next year. Anyway, your answer is yes, just be certain to contact me after this auction is over. I would be delighted to send you the schematic. Good luck! Bob Carver
Q:  Can the transformer be tapped for 240volts ac use? Would you consider shipping overseas? I have a FedEx a/c to facilitate this. Nov-19-08
A:  Hi 'le8, I CAN make it operate overseas, and yes I have the technology to ship to any place in the world. I'm sure your Fed-Ex account will make things nice and easy, thanks for asking and joining. Warmest and best regards, Bob Carver
Q:  Hello- I have a question regarding negative feedback that turns into positive feedback with some circuits. The question was sent to your gmail address along with a diagram of the squealing circuit. Did you get a chance to look at it yet? I am curious as to what I'm doing wrong. Thank you in advance. Blair Nov-19-08
A:  Hi Blair, I've been out of town, but I'll find that e-mail and contact you this weekend, or Tuesday at the latest. We will fix it for sure! Bob Carver
Q:  Hi, Bob, I am from Hong Kong. Just curious but I am serious, will you and Tim together design and build a power amp best for driving Peter Walker's early QUAD electrostatic speakers, i.e. ESL57 and ESL63. I'll be in the waiting queue. Nov-19-08
A:  Hi 'yyu, I'll ask Tim next week when I return home - the main problem is the time it takes to design it AND get it right. Tim and I both have a love for the old Quads - for me it was the first time in my life I heard an amazing speaker. Perhaps we can tap into that old love of QUADS. Keep your fingers crossed.
Q:  Hi Mr. Carver, If I won the bid is it possible that you could convert the amp to 220V. I intend to use them in Thailand. Thanks. Nov-19-08
A:  I will adapt these amps to operate on 220 volts. No problem. Happy bidding and lots of luck! Thanks for asking, Bob Carver
Q:  Hello Mr. Carver, as a vacuum tube amplifier scratch builder and honoured student of Lance Cochrane, I can really appreciate these two massive units you and Tim have created! Very nice to see you enjoying tube technology. To me, it's just so much more fun in every way than transistors could ever be! Also nice to see that Lance had a hand in getting you involved in the ebay experience. You are a very well respected man in audio, and to own something with your name on it is truly an honour! P.S. Just so you know who I am, you recently saw my work on my new web site. Steve- Peterborough Ontario Canada Nov-18-08
A:  Hi '748, Steve, I saw, admired your work and completely identified with your passion and creative drive to build something better and out of the ordinary. What better place than in the world of vacuum tubes? Your amplifiers are beautiful; each so unique - seems we were both inspired in important ways by Lance. Thanks for your comments, keep up your good works, Bob Carver.
Q:  Hello Mr. Carver, I can't tell you how inspiring it is to see these beautiful amps! I used to design and build tube amps as a hobby in the 60's, and now after 35 years I am back at it again. I am so excited because now we can make them sound even better, and your DC Restorer circuit appears to be a solution to an age old problem. Have you published the details or schematic of your DC Restorer anywhere, or would I be able to get a copy from you? Thanks, John (access_guru) Nov-18-08
A:  Hi 'ru, John, I'll send you a copy about a week after the auction closes. I'm out of town right now (on the road) and I'm following our auction from my hotel room. If you contact me later in about a week or so, I'll send the schematic and a parts list. I have to say, there is nothing more fun than building vacuum tube amps. Thanks for writing, Bob Carver
Q:  Hi, Bob! I have read in your replies that you can share schematic of this amp after auction end. May I ask you the same favor? Nov-18-08
A:  Absolutely! My pleasure. Just don't forget to call after the auction. Thanks for asking, Bob Carver
Q:  Dear Mr. Carver, I am very excited to see a pair of amplifiers designed by yourself and Tim De Paravicini. Unfortunately, I am unlikely to be able to afford to purchase them and was wondering if you would be willing to make the schematic available. i would like to try to build a copy for my self if you don't mind , i was allwayes want a amp from you , so i want to ask if teh scematitic is all i need to get help and do a copy regards yehuda Nov-18-08
A:  Hi '972, Vacuum tube amplifiers are fun to build and listen to; I'm happy to make the plans available, along with some good tube amp counseling along the way as you enjoy the adventures of buiding a pair. My head is swelling - thanks for the accolades - makes my day! Just contact me about a week after the auction is over to help me remember this promise to you. Thanks for writing, Bob Carver.
Q:  Bob, You asked me to ask Ed Dell about publishing the schematic for this beast. [BTW, I changed my EBay ID from "nation_sauna_wholesalers" to this new moniker, "technicalaudio", in case you're wondering]. Here is Ed's reply, verbatim: "Hi Brian Thanks very much for thinking of ax as a path for those interested in Bob Carver's new amp (what a marketing genius he is.) I would be happy to publish the schematic. I would also request permission to use one of the photos he has posted on e-bay (not the one with him eating the apple(or hotdog, however) and also a parts list. He may question adding the parts list since with it people may construct the amp themselves. The smart ones will figure this out without the list, however. This is a great opportunity for us, since every bit of news about ax helps spread the word about DIY. It is nice to have long-term readers who do the creative thinking for you. Thanks Best Ed" (ed@audioxpress.com) I'll let you contact him directly. Thanks! Brian Nov-18-08
A:  Hi 'dio, I e-mailed Ed this morning and said I would be delighted to share these amps with his readers, including schematics, parts list , and helpful hints. If he wishes of course, but I have not heard back from him yet. Many years ago he ran the complete plans for my big Silver Seven tube amp, and I actually met several builders who had built them. I couldn't believe it! But it was true! Thanks for the important idea Brian. Best wishes and warmest regards, Bob Carver.
Q:  Hi:I'm hoping youall can helpme with my telefunkn fome Belg. Everything is in German.Its a Conceritino#7The 110 side of the power supply burned out. Can you be of some help.Is There an out of the unit(radio) power supply THE 220 WORKS THE TUBES COME ON. .Thank you for time Michael D.Ross (760)672-7515 Nov-16-08
A:  Hi birdman, Of course I will help. Contact me about a week after the auction for a scientific discussion about burned out power supplies, and we will almost certainly get your amp up and running. Looking forward to our amplifier science talk, Bob Carver
Q:  hello mr carver-- beautiful pieces! wondered if you have considered making affordable tube gear for those lacking funds to own things of this caliber. i bought one of your 400 amps in the 80's and loved it, bought a 400t a couple years ago from ebay and it was awesome as well. currently using a tube amp from a wonderful fellow that sells his amps on ebay from california you may know. i think that you could sell them as fast as you could make them if you had a similar piece with your name on the front. just a thought. again, beautiful!!-- Nov-16-08
A:  Hi '914, You are making my head swell a bit. Thanks for the kind thoughts - and if the fellow from California happens to be Lance, know that it was he who gave me the idea of doing an eBay amp - it seemed to be lots of fun meeting so many tube amp lovers. Thanks for writing, Bob Carver.
Q:  Mr. Carver: I'm a poor student. Actually, I'm a very good student, but am poor of means. I have always thought highly of many of your products, including the Amazings. I would like to beg a copy of your schematic as well, if you would be so kind. Please put me on your list. Thank you very much. Indeed grateful. --Robbbie Nov-16-08
A:  Hi'piv - Robbie, You are on the list! Please contact me after the auction is over to get your copy. I was a broke student too, so I hope the schematic helps you as much as tube amp schematics helped me when I was a student. Best wishes and warmest regards, Bob Carver.
Q:  Mr. Carver: I'm a poor student. Actually, I'm a very good student, but am poor of means. I have always thought highly of many of your products, including the Amazings. I would like to beg a copy of your schematic as well, if you would be so kind. Please put me on your list. Thank you very much. Indeed grateful. --Robbbie Nov-16-08
A:  Hi'piv - Robbie, You are on the list! Please contact me after the auction is over to get your copy. I was a broke student too, so I hope the schematic helps you as much as tube amp schematics helped me when I was a student. Best wishes and warmest regards, Bob Carver.
Q:  Hi, Bob! I have read in your replies that you can share schematic of this amp after auction end. May I ask you the same favor? Nov-16-08
A:  Hi'_ba, Yes, I would be delighted. Just make sure you contact me about a week after the auction is over and I'll send it to you. I'm out of town for the next ten days and will be answering questions from afar from my hotel room, but I won't have a schematic until I return home. Thanks for writing, Bob Carver
Q:  Dear Bob Carver: I sad to say am in the group that most likely willnot be able to afford the final price of these amps, but must say they are indeed beastiful! (Probably the most beautiful item on EBAY except perhaps the K model Beechcraft Bonanza! Thanks for all thec info I appreciate it Tom Nov-15-08
A:  Hi 3550, Tom, Thank you for the accolades, even thought the Beechcraft IS prettier. Perhaps the last sentiment depends on whether we are pilots or tubaphiles that glow in the dark. I'm glad you liked the techno information - I often think I'm putting all of us to sleep when I go on and on with so much technical stuff. Thanks again for writing and for your comments, Bob Carver
Q:  Hello Mr. Carver, Im down in Seattle and would gladly come pickup the amps and pay cash to avoid all the PayPal Fee's. Is that acceptable? I did read where you said you would come set it up etc. if the buyer was close. If I win these, They will be put away for awhile until my new home is finished and a large listening room is designed around them. About 9 months out right now. Thank You for your consideration. Nov-14-08
A:  Hi '217, So you live in the rain-forest too! Well, if you win, come on over to my place and we can listen here before they begin their long hibernation, to be awakened like Sleeping Beauty with a kiss nine months from now. Best wishes and good luck! Bob Carver
Q:  Hi Bob I'm not an audio engineer type,but I love great sound,BTW your amps look great! How come no American Co. has marketed/made affordable great sounding, self bias (for the wider market)tube integrated? China's doing this, I have bought some Eastern Electric goods and they are fantastic, among others, I think there's a market for it here. Still lots of two channel freaks. Any thoughts? Regards,Eric Nov-14-08
A:  Hi 'rick, I really don't know why American guys don't build integrated tube amps. Personally I think it's a great idea, and I know that in the vintage days it seems that everybody did. Lafayette, Citation, McIntosh, Fisher, Scott Boulevard and on and on endlessly to name a few. I also know there are lots of us two channel folks. HUMMMM? Bob Carver
Q:  Hello Bob I guess you were "just blowing smoke" when you responded to my e-mail promising me that you woulod send me a schematic and pictorial drawing of the last pair of Mono Blocks that you and Tim de Paraficini designed and you and Tubular Joe built) that you sold on e-bay, to use my pair of output transformers Regrds, "jay" Nov-13-08
A:  Hi Jay, Man, am I glad you have e-mailed me! I lost you when I had my computer scrubbed clean of viruses by a computer guy. I goofed up. Anyway, now I have found you again and will send you the schematic just as soon as this auction is over. I promise! Please contact me then via my regular e-mail just to make sure I don't forget. You're back! Yea! Warmest and best regards, Bob Carver.
Q:  Aren't you the same Mr. Carver that proved that a modestly-priced solid-state amp could be made to sound EXACTLY like any other amp, tube-types included? What has changed? Nov-13-08
A:  Hi '618, Yes, it is I, the real Bob Carver. Nothing has changed. What I did at Stereophile so long ago was to show that I could get very, very close. Within one part in better than four ten thousandths, but not EXACTLY. You can read all about it by Googling Carver Audio.com and clicking on "Carver Challenge", or just Google "The Carver Amplifier Challenge" It's surprising to me that after all these years, the article is still being posted in so many places around the world! Thanks for writing, Bob Carver.

 
 
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

[b]On loan: C-16 preamp

Blue Mouth Promotions LLC Where the music matters most!
1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
weitrhinoOffline
#4 Posted: Saturday, August 15, 2009 9:26:18 AM(UTC)
 
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weitrhino

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Question & Answer Answered On
Q:  NO question, but, as a hi-fi enthusiast who will probably never actually MEET Bob Carver, I wanted to send my kudos to a gentleman who efforts, persistence, and never-ending search for perfection has meant so much to a hobby that so many, of all backgrounds, enjoy. Kudos, Bob. Neil in Kansas. Dec-30-08
A:  Hi Neil '43. Who knows what life holds; you have made my day with your kind cheers and nice smile. Happy new year, Bob Carver
Q:  any chance of getting, buying or otherwise obtaining a circuit diagram for this fine amp? I am not quite in a position to compete for this amp now. thanks, bob m Dec-30-08
A:  Hi sly bob69,I would be happy to send you a circuit diagram. Send me you e-mail and I'll send it within a week of the auction closing. bob.sunfire@gmail.com.
Q:  Mr. Carver, I was diagnosed a few years ago at 28 with a tumor on my acoustical nerve. I started to revisit audio shortly after. Being out of work do to my illness I had to sell off my gear. A great friend of mine has been by my side since day one. He put some funds together and got me a new setup. He couldn't afford this but made it happen. Well I had a fire and lost that gear too. so there he and I were with a passion for audio and no gear. "Life goes on".... A short time ago I found out my dear friend is terminally ill. He is bed ridden until his illness takes its toll. Backing up a bit I have spoken to him about who you are and what you mean to the audio world. He called me frantic last night..."get over here man I have to show you something" So I quickly got some shoes on and headed over. When I got there he was literally jumping up and down.. He couldn't show me this auction fast enough. Sure we cant afford these but it didnt stop us from dreaming...Thank you for that. AMAZING! Dec-30-08
A:  I am silent, and I'm weeping. What a beautiful story; thank you for sharing it with all of us. Bob
Q:  Amps are awsome. I myself also love to design and build tube amplifiers. I would love to meet Bob Carver. Could this be aranged? I would love for him to see my designs and projects. Ron Becker Dec-29-08
A:  Hi '32 Ron, I would love to meet and have a scientific discussion about tube amps; there are few meetings that could possibly be more fun! Come on over to my place or to the Sunfire building if you live close by. Or even if you live far away. Bring your designs, I'll bring mine. If you live too far away, we can even do it by e-mail. Many Cheers, Bob Carver
Q:  Bob and friends, your design here appears well thought out and executed. May I ask, is your .15% THD at 180 watts output a midband measurement only? How do things hold together at your rated 23HZ and say 20KHZ where things usually get hairy? =:-o And in your experience, how audibly important are the ends of the humanly perceived spectrum? :>) JAY Dec-29-08
A:  Hi '4298 Jay, This question is deep and complex, even deeper than you probably think; I love questions like this! Here goes. My (full power) 0.15% THD spec is at one kHz, whereas at 23 Hz it's just below 0.5%, and at 20 kHz it's about 0.35%. My THD analyzer has a 50 kHz measurement filter that helps my measured 20kHz number a bit. My transformer core begins to saturate at 707 volts rms (end-to-end) and 0.043 seconds. Nothing like those old vintage transformers! As far as frequency response goes, I like flat response to the ends, but power response at those ends is far less important, and in fact not important at all in the extreme. As an example of this, consider the RIAA curve, whose POWER response is down approximately -20 dB relative to 1kHz. This means the tweeter of a 200 watt system will never see more than about two watts! We can easily see this in our designs; a woofer voice coil weighs around a 1/4 lb (like a good hamburger), and a tweeter voice coil weighs about half a gram. Less than the tracking force of a cartridge on vinyl, and clearly unable to dissipate more than a few watts. This implies that full power from an amplifier at 20 kHz is not needed at all, and all who have seriously designed and listened to amps have come to realize this sooner or later. And of course the folks who designed our RIAA and vinyl system did so long ago. Still, power response is different from frequency response; since our human hearing mechanism normally extends from 23 Hz to 22kHz, and our threshold of feeling curve crosses the threshold of hearing curve at 23 Hz (in a normal human being of average physical dimensions capable of lifting big tube amps), we do need to go that low. Beyond that, 22 kHz is the normal upper limit for an eighteen year-old who has not been in a rock band. For the rest of us, we must have the music a few dB louder in order to get above our hearing threshold at 22 kHz. Thanks for asking a great question! Bob Carver
Q:  Do you have any other amplifiers for sale? Thanks Dec-29-08
A:  Hi Mark '98, I don't have any more tube amps that I built, but I DO have lots of vintage tube amps designed by the Masters of time long ago. I may put some up for auction in the near future; I wish I had some ready to go right now for you, but I do not. Keep in touch. bob.sunfire@gmail.com Thanks for writing, Bob Carver
Q:  All I can say is "Holy-Wa"! Someday my fortunes will change..... Beautiful! Thanks for showing these! Rod KB8DNS Dec-28-08
A:  Hi Rod 'DNS, I assume "Holy-Wa" is almost the same as HOLY MOLY ROLLERS! Like Captain Marvel (Billy Batson) used to say. Did you know DNS means "do not stuff" when appended to a schematic; it means the designer doesn't know if she or he wants the part installed or not. Happy new year! There is no doubt in my mind at all that your fortunes will change; they always do every day. Thanks for writing, Bob Carver
Q:  Good Evening Bob, I Just wanted to tell you that I enjoy and am getting an education just reading the "Question and Answer" part of your e-bay auction, I enjoy it very much. The best of luck on this sale and I will say "Happy New Year" and prosperous 2009 Bob Carver. Best Regards, Jay Fletcher Dec-28-08
A:  Hi Jay, Thanks for taking the time to write, for I've enjoyed being a teacher once again, and I'm glad you are enjoying the Q&A part as well. Thanks again for wishing the best of luck. Happy new year, best wishes and a great year! Bob Carver
Q:  HI AGAIN YOU LOOK GREAT .THE MOST TRUSTED MAN ON EBAY. ...AGAIN THE BEST TO YOU ,HAPPY NEW YEAR FROM BRUCE AND CARLA FOREVERMUSIC414 BALTO MD Dec-28-08
A:  Hi again 'music 414 Carla and Bruce, It's my big straw hat that makes me look good(?). Must be..... Happy New Year and all my best, Bob Carver
Q:  Can you send it to Beijing? Thanks Kobemin Dec-28-08
A:  Hi 'min, We do possess the technology to send it to Beijing. Actually it's not me, rather it's Boeing, Airbus, United Shipping, Far East landing Co. and many others including UPS or Fed Ex. Not to mention at least two governments. So the answer is yes, we can send it to Beijing. Bob Carver
Q:  Can we get " Tubular Joe" to sign off too??? I have so much Carver stuff it's embarrassing!! Will you help me with set up if I win??? Thank you so much for your everything!!!! Dec-27-08
A:  Hi 'king, You bet, all three of us! If you live close by, I'll come over to your home and help. If you are far away, I'll still help, but we'll do it by phone, e-mail and lots of talking. I sort of understand embarrassment, as I have too have lots of Citation amps, preamps and tuners. Best wishes and lots of luck, Bob Carver
Q:  Does this work in 220v or do I need an adapter? If I need an adapter, would something like this work? http://www.110220volts.com/ATVR-1000.html Thanks a lot. Dec-25-08
A:  Hi '871, This amp can be wired for 220 volts or you can use an adaptor,either way. The ATVR-1000 will work great;one unit will power both amps. Good question, thanks for asking. Bob Carver
Q:  Hello Bob, Good to see you. I am still listening to your Phase linear Model 2000 series II, and Model 200 series II amp and preamp. Since parts are hard to get and they are 30 years old, any chance for you to come up with new circuit for their chassis to keep these fine vintage equipment going? Thanks, Joe Dec-25-08
A:  Hi '123, No problem and no worries. Rita helm, the best fix-it true lady in all the land, has recently started a service shop to do just that. She has worked for me for over 20(!) years repairing and updating vintage Phase, Carver, and Sunfire equipment. She's famous! Send it to: Rita's Vintage Audio Service, 1920 Bickford Ave, Snohomish, WA 98290. Or call her at 425 530 9557 good luck and thanks for writing, Bob Carver.
Q:  Hello Bob Carver, Mr. Carver I did not know at the time that I started writing to you that man you are a LEGEND and I am not "Blowing Smoke" </:-) Merry Christmas Bob!!! Jay Fletcher Dec-24-08
A:  Thanks Jay, Merry Christmas to you as well! WOW! Your icon really does look like Santa. I'm going to try it. </:-) Oh well, for some reason my letters spaced themselves out too far. I tried. Pehaps the letters will space correctly when I push the "send" button. Cheers, Bob Carver
Q:  I'm interested in learning more. I have built a state of the art sound room in NYC it's first class/ better than any dealers and I am moving this hobby towards becoming a business. I am currently a dealer for Wadia digital, ATC speakers, Analysis speakers, sme tone arms, ortofon products. I had a very bad experience with a Japanese solid state amp builder (technical brain). I've come running back to tubes. I've been into rolling tubes in other equipment I own and am stunned by the magic I'm hearing. I really liked the story behind your products and would like to explore more. Can you build a similar more powerful Amp? The sound room speakers the largest and best of speaker companies. Please advise... Bill Dec-24-08
A:  Hi Bill '005, I for one cannot imagine a business more rewarding than audio. Lots of hard work of course and bumps along the way, just the same, NOTHING is more fun. There is no doubt in my mind but that your efforts will be super successful. And yes, I can build a similar and more powerful tube amp. An easy walk in the park, only problem is I would have to rob my museum to get all the vintage parts, or search the world for new ones, or make them myself (output transformers). If you have some pics, I'd love to see them. bob.sunfire@gmail.com Thanks writing, Bob Carver
Q:  Hi there Bob - I saw your posting for the new amp - good to know you are still around and doing TUBES - in my collection I have 2 Citation I's and 2's - Do you contribute any forums, websites, discussion groups ? I would love to find out more about the DC fix you mention - Gary Boyd Dec-24-08
A:  Hi Gary 'lues, I don't, but it's never too late, right? I had lunch with Stu Hegeman (the designer of the Citation equipment) around the time he came out with his HAPPY 1 preamp, and left that long and extended lunch meeting with many of his ideas and thoughts burned into my brain. What a genius he was! He showed me several important up-dates for Citation 2's, and I will be happy to share them with you if you contact me after the auction. That goes for my own DC restorer as well; I've put it into every Citation tube amp I own, along with Stu's up-dates. Anybody else want the information, just contact me as well after the auction. bob.sunfire@gmail.com Thanks for writing, Bob Carver
Q:  My gosh, that's great! Keep up the good work. Hope you make plenty money and keep making amps. Best regards, Ray Harvey Dec-23-08
A:  Hi Ray '1919, Thanks for the nice thought and for the enthusiastic cheer. I'll always make amps; couldn't stop even if I wanted to. As I've often said - Bob's my name and amps are my game. Hey Ray, you can be my friend forever! Bob Carver
Q:  Hello, Bob. It has to have been close to 35 years since I attended one of your gatherings (in NYC, though for the life of me, I can't think where . . . Harvey, Lyric or Liberty, perhaps?) It is great to see what you've been up to and you have certainly piqued my curiosity. Is there a third amp available (the Citation has a center channel out, I believe)? And, as a side issue, can the ceramic input on the Citation be modified to a moving coil section? I had the I and II back in the day mated to Altec A-7s,then to some speakers of my own design. I always admired the Citations. The pre-amp was a particular favourite. Currently, these would drive EV TRX-15s in restored Karlson cabinets . . . if I decide to do it, of course. Everyone's business, including mine, is tapering off. Great to see your enthusiasm is still so strong! Dec-22-08
A:  Hi '46 Bob, I can't remember either - probably Lyric with Mike Kay. Oh well, at least I do remember the gathering, and yes the ceramic input can be modified for MC. A walk in the park! And I've done it already. And it retains the Hegeman phono-stage magic. If you bid and win, and would like this update, no problem at all. Happy to do it. I have wonderful memories of working in Seattle Stereo Center where we carried TRX-15's, but not in Karlson cabinets. Hey, we are in the arena with no early out. One last thing, these are mono blocks, so an odd one (three)is easy. Thanks for writing, Bob Carver
Q:  HI Bob, I'll throw in my two cents since I have first hand knowledge. Sorry I havent gotten back to you on the amp points we discussed but Ive been running different pre-amps and Speaker combo's hoping to settle on one and then get back to you but I gotta tell you, These things are like a Ritz Cracker, Everything tastes great on them. I ran one of your old C19's into it as well as a Marantz C45 and a really sweet Linn. Ive been looking for some tube pre's to audition and now you decide to offer a Citation also! Well, to let everyone know, all I can say is these are truly amazing and worth every penny I paid, and then some. I think I might stop by the repair shop next time Im in that neighborhood. Arent you in Cahoots with a repair shop there? However, I'll get back to you. Have a Great Holiday and Thanks Again!! Dec-21-08
A:  Hi again '217, Good to hear from you, and glad you like the amp and think it's truly amazing! - you made my day! Really have. Ritz Cracker huh? I always thought more like a chocolate covered peanut butter cookie. You have a great holiday too, thanks for writing. Bob Carver
Q:  Choosing Iron and Winding Transformers. Cont...? Dec-21-08
A:  Hi 'blondies, Since these massive and expensive transformers were wound during the Golden Era for tube amplifiers, they were wound on the best core that money could buy at the time. However it was tough for designers of the time to get both low frequency core saturation and high frequency leakage inductance to vanishingly small values simultaneously, as these properties are almost mutually exclusive. Back then even the best transformer steel("iron")was not nearly as good as it is today, and in order to obtain the best performance, various artful winding methods were used to get it right. The way they did it was to wind many, many sections, interdigitated, interleaved and cross-wound while all the time insuring minimum leakage through the use of bifilar nesting of the wires inside the transformer. It became a true art form mastered only by a few. Today we can count all the great vintage output transformers on one hand alone. And they are and were EXPENSIVE! Today we have much better steel (though copper wire has not changed much),and different winding methods have evolved to take advantage of the new steel. A simple two or four interleave is the normal way it's done today. Dirt cheap by comparison. I think I loved my transformers more than my girlfriend when I was in college, and I don't know what I'm going to do when I run out. I have my old transformer winding machine; perhaps I'll just copy these using the vintage winding methods but with modern steel. I'm not out yet, if I can only find them. Fascinating question, thanks for asking.
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

[b]On loan: C-16 preamp

Blue Mouth Promotions LLC Where the music matters most!
1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
weitrhinoOffline
#5 Posted: Saturday, August 15, 2009 9:36:04 AM(UTC)
 
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weitrhino

Medals:
Senior: Black Pearl device for multiple award; senior memberSite Builder: Black Pearl device for multiple award; major contributor to the Carver site! community.Yin Yang: Black Pearl device for multiple award; participated in audio Karma
Cee-Bang!: donated to fund CARVER site! hostingFeatured: systemCarver modified: Carver mk II, or self-modified owner
Music: extensive, varied collectionGreeter: most welcoming to new members

Rank: TO-247 Transistor


Groups: Resident

Joined: 1/19/2009(UTC)
Posts: 2,408
Location: Wichita Falls, TX

Was thanked: 858 time(s) in 598 post(s)
Gave Thanks: 773 times

This one is a repeat of the first posting in this thread, except having come from the original auction pages each entry is date stamped like the others above and that's the only reason I post it here.
 ===============================================
 
Question & Answer Answered On
Q:  Hi Bob, redstone7 here again from Colorado Springs, I have to ask one more question......is there ever going to be a tube preamplifier offered from your camp right here on E-Bay??? Thanks much, Rob Mar-21-09
A:  Hi Rob'stone7, not from me ( I should never say never), but James Sauter IS planning to build an exact copy of the preamp I designed for the Silver Sevens long ago. He may be found on the Carver Fest forum. Thanks again, Bob Carver
Q:  continued,, so now there is being fed to the bias pot a filtered neg. DC, that is decoupled from the filter capacitors, that can change with without the lag that a capacitor would cause. It must have been pretty darn fast because I could hook the amp to a scope,set idle to 15ma. suddenly zap a sinewave to it big enough to drive right up to just before clipping, and the sine wave would instantly appear with out gradually climbing up with flattened tops. That was good enough for me!!!!! I have bailed out of tube equipment, am now making chip amps from the latest audio grade offering from National Semiconductor.. they sound very "tubelike" to me (and many others) Just in time because I am getting too old to manhandle heavy iron. nevertheless I still maintain a keen interest in new ideas in tube technology. I would love to see a schematic of these amps..could you send me one to my email? The 6al5 is a high perveance duo diode.I'm trying to imagine how it is implemented..Neal Mar-21-09
A:  Hi Neal, I would be happy to send you a schematic....just e-mail me after the auction to remaind me. Don't forget to include your e-mail! Bob
Q:  Greetings Bob, I have followed you since the Silver 7, and Tim since the EAR, and I can not think of any other two who have added so much good music to the world. In fact reading of the Silver 7 is what got me interested in tubes...again (built my first tube amp in '57 with bits and pieces of discards, but cost drove me to transistors in 65 and cheap speakers masked the difference). Might it be possible for you to come up with a "kit" or built bias 'controller' that would be adaptable to different amps. I have a Meas Baron tri-tube modified which I love, but 1 bias and 1 balance pot to control 6 tubes per side requires frequent tweeking even though I use current matched tubes. It seems there is much interest in a better bias method. I have seen this in questions for the amps you have offered, and in many of the DYI groups as well. Many not be exciting to do, but it is a much needed product, and important tweek for tube amps. I you'd be swamped with sales too cordially, bud Mar-21-09
A:  Hi 'greg, I too have a pair of vintage Mesa Barons with six 6L6's per mono block amp. Beautiful amps! The 6AL5 DC restorer is the answer to your problem, plus it will stop the DC bounce that inevitably creeps into the system as the grid bias "hunts" under dynamic conditions. E-mail me after the auction and I'll send you the complete fix and the schematic as I used in my Baron. Warmest and best, Bob Carver
Q:  Hi Bob...thank you for responding to my confusion concerning your bias scheme,,but first I want to say to the bidders:....BID AWAY, BOYS AND GIRLS.I HAVE INDEPENDENTLY DUPLICATED THE ESSENTAL FEATURES AND CAN ASSURE YOU THIS IS THE ONLY WAY TO OPTIMIZE FOR AUDIO QUALITY AND LONGEVITY. SO BID WITH ASSURANCE MORTGAGE YOUR HOME IF YOU CAN GET ONE OR EVEN HAVE A JOB LEFT TO THINK ABOUT IT Ok I think I know where my confusion lies----when I say sliding bias I mean changing the G1 negative voltage....when you say sliding bias you refer to a particular TECHNIQUE to change G1 neg. volt. Consider the neg source half or full wave, there will be a smoothing cap followed by a an RC tage ,followe by maybe another RC smoothing stage..Now follow with a resistor voltage divider WITH NO CAPACITOR ..the center connection now feeds the bias pot..One leg of the volt divider is paralleled with a device that changes resistance with input drive....continued Mar-21-09
A:  Not exactly, but close enough for Gov'nt work. Keep that brain going 1000 RPM and we can have a scientific discussion about bias off-line. Bob
Q:  dear Bob....thank you for hanging in there with my audio-amatuer forays into mysteries of tube amps. I don't understand your bias stablization...it doesn't jive with your comments which I quote here "the dc restorer eliminated the need to idle each output tube at 50 watts yielding instead an idle power of 12 watts per tube....It works by keeping the dc componant on each output tube grid the exact value throgh the entire audio signal swing allowing perfect performance up to and even beyond clipping" Well, if by dc componant you refer to the negative bias grid voltage this is exactly how I describe my sliding bias scheme. If your bias scheme doen't shift the negative bias as the amp moves away from idle it will soon run into class B operation and really gross distortion. Your previous response says the bias doesn't slide , but if by slide we mean changing the bias voltage , then it MUST slide to my way of thinking...I'm confused cordially neal Mar-21-09
A:  Hi '541, ....It jives perfectly with my comments. A sliding bias scheme has too much delay in responding under dynamic conditions OR it has too much control voltage ripple modulation for my taste. Such a scheme must ALWAYS be a compromise between the two. That's because it will have a detector diode, an integrating capacitor, and a time constant comprised of the final smoothing RC filter. The topology is often similar to a meter drive circuit. On the other hand, a DC restorer operates such that the DC value of the waveform on the grid remains where we want it even in the presence of asymmetrical, haversine signals. And its delay time is essentially zero because there is no filter capacitor to charge and therefore no time constant. Works far better, and is far more elegant than a simple and coarse sliding bias circuit. Bob Carver
Q:  Bob....Come on..Bob..don't you want to explain to the prospective buyers the magic trick of 12 watts idle ( 18ma. at 660 volts anode) per output tube and not slide the bias to lower and lower negative G1 volts under progressively greater dynamic conditions to keep out of class B operation and unlistenable distortion?? ("My dc restorer is not a sliding bias approach, rather its purpose is to keep the DC value on the control grid at design center etc etc" your words , not mine) we are all waiting with breathless anticipation cordially Neal in Oregon Mar-21-09
A:  Continued next following.
Q:  Hi Bob, can you say a bit more about how this amp sounds? Can you elaborate on "the sound: This amplifier stands with a small handful of the world's great vacuum tube amplifiers" a bit more, especially sound-wise, which of the great amplifiers are most similar to your amp? Thank you, Frank Mar-21-09
A:  Hi '211k, I would say my own Silver Seven's, my Subsequent Silver Sevens with extra output tubes and dual screen regulators. (Two 6550's per amp.) The $30,000 Manley amps, and the Mesa Barons at 150 watts. I've limited this to vintage amps. Hope it helps, Bob Carver
Q:  ...which output tubes are used in this amp, 6550's or the kt88's, the write up refers to both articles tim depravacini/stu hegeman and yourself, is there any difference between the carver/pravacini mono's and carver/hegeman mono amps? thank you! david Mar-21-09
A:  Hey old friend, these amps use KT88's. The difference is in the front end; these use 12AT7's, 12AX7's, and 6AL5's with KT88's. The Hegeman units use 6AW8's, 12BH7's, and 6AL5's with 6550's. I cannot answer the question which one do I like better because it's just like asking which of your children do you love more. I love them both the same, even though they each possess distinctive audio personalities! Bob Carver
Q:  What an honour to be able to ask you a question,Bob. How do you think these amps would match up with Apogee Duetta Signatures' current and voltage loads, and would you recommend running both MT ribbons and bass panels with them ? (Trying to get away from present biamping with chip amps on bass and tube hybrids on MT ribbon and into a more coherent one-amp sound, if that makes sense). Your vintage pair here have come up on the Apogee users' website as one possible ultimate amp for Apogees, which would be wonderful for one who, like me, is just looking for that final and permanent piece of his system. Mar-21-09
A:  Hi 'fitte, I prefer the one-amp coherent sound unless the amplifier is not powerful enough to avoid clipping and overload on some of your music. This amp has been designed to run the Apogee Scintilla one ohm speaker....I really worked hard to get it to do that. So it should be a walk-in-the-park for the Duetta. The power increases as the impedance decreases....up to 300 watts, just what the Apogee needs and loves. I would not bi-amp here, perhaps bi-wire with heavy gauge for the bass panels and finer wire for the ribbons. Try it both ways. Bob Carver
Q:  Hello Bob, I was reading your writings here and you mentioned that your friend Stu liked the 6550's better than the KT-88's but I see you opted for the 88's on this design,is there a specific reason because of the overall design or is it more about personal preference? The funding is not here to bid on your current effort but I'm right in the middle of re-tubing my MC-275's and your input would be greatly appreciated , Thanks, Rob McRae in Colorado Springs Mar-20-09
A:  Hi 'stone 7, Remember that Stu was designing tube amps long ago and the KT88 was very new on our shores. At the time, the mighty 6550 was supreme, was considered the best and the finest, and was used by all the great designers back then. However, the KT88 was on its way. I love both tubes and would be happy with either, but I have a giant stash of NOS vintage KT88's to use from my museum. Bob
Q:  Hello Mr. Carver, is there any comparison between these beauties and the legendary Silver series of tube amps you created long ago ?? Could they realistically be produced again, given the growing high-end audio gear market, especially in the tube sector ? Since I was unable to attend CarverFest last year, I'm still hoping to view the Q&A session that was recorded , I submitted questions for you and have yet to learn what your answers were ! Maybe this year !!! Respectfully yours, silver7t1 Mar-20-09
A:  Hi '7t1, Oh no! I never got your questions, or perhaps I did and have forgotten. Try again at bob.sunfire@gmail.com., The relationship between the two amplifier designs is what I call crystalized knowledge. The Silver Sevens are similalar to the 520 circuit, whereas these have the cicuit described above. You bet this year! Bob Carver
Q:  Hello Bob I consider it a honor to even ASK you a question, let alone receive an answer!LOL Anyways I'm wondering about the transformers, can you disclose what they are for primary Z? Also I don't see a choke in your PSU, is it CRC filtered then? Thanks WOT Mar-20-09
A:  Hi 'tour, I have hooked them up to match four output tubes, so in this design, since I have six of them they are intentionally underloaded which allows them to operate such that an easy 180 watts is obtained, and is the reason the output power can increase when havily loaded with a difficult to drive speaker load. All CRC filtering, and with so much that a vintage designer woul find it difficult to believe.
Q:  Bob - Oops, forgot that the text mentioned the bias control. I am fascinated by the driver. It looks like a 12AX7 sized T-6 tube, short envelope. I would be interested in finding out what it is. Again, it looks like a 5687. Tim Smith Mar-19-09
A:  It's a 12AT7 double mica, military frame grid NOS tube and can easily drive three outputs per plate with a 33,000 ohm resistor following. See the RCA tube manual. Excellent question. Bob
Q:  Bob- Will you ever decide to release this tube amp design for production commercially? Mar-19-09
A:  Hi '1, I would love to but that would take more vintage parts than I have to spare. I don't know what I'll do when I run out of output transformers, but I'll think of somthing....maybe I'll just clone a Partridge or something, as I still have my old transformer winding machine.Warmest and best, Bob Carver
Q:  Hey Bob---just let 'rama know he can find me by going to my eBay page. He can go to the site map, click on find members, and put in tubular_joe. Thanks! Mar-19-09
A:  Got it! Bob
Q:  Bob - Magnificent amps! A few questions but don't the feel the need to answer if you'd be compromising proprietary information. It looks like the KT88 grids are fed from the 6AL5 cathodes - can't tell, the chassis photo is grainy. Also, are all of the KT88s controlled by a single bias pot (rear of amp?) or does your circuitry handle bias needs - can't tell if there's a bias pot at the rear. Is the driver tube a 5687? That strikes as about the only small tube (non-Russian) that would have the ability to drive a sextet of KT88s. I've built amps for several years, essentially all with regulated pentode output stages; think they sound the best. I recently finished a 45 watt/channel rig that uses Russian 6P41S vertical amp tubes run at 460 on the plates and 185 on the screens, If you're interested I can send photos; email address is tim.e.smith@bhpbilliton.com. Good luck selling these, I hope they find a good home. Thanks, Tim Smith Mar-19-09
A:  This is going to be a fast answer...I'm on a two minute time-out computer. The drive comes from a 12AT7. The 6AL5 IS connected to the grids to control the D.C. All the output tubes are cintrolled by a single pot, not for balance so much as for the ability to trim the soundstage envelopment. And yes I would love to see see photoes.
Q:  It is a pleasure and a privilege to view your tube amp and to read your Q&A. You are truly a designer for the people, reminiscent of when you took the Stereophile challenge and made affordable gear sound like reference. Sorry for the off topic question but I am dying to know if there is a postscript to the challenge. Cheers! Mar-19-09
A:  Hi 'it, Well, the only postscript that comes to mind is that after all these years, the original article is still being posted around the world in several languages and many forums. It suprises me to this day that a single article by J. Gordon Holt has had so much staying power. Thank you for writing, Bob Carver
Q:  Dear Bob, Another thought I have is concerning your comment that only four types of circiut designs for tube amps have ever been invented. With your design being a 5th circuit, would it have been possible to design this circuit 50 years ago with the type of componets available at the time or would you have had to add a bunch more tubes and circuits to accomplish the same design 50 years ago. Am I making any sense? Thank you again, Frank E. Mar-19-09
A:  Hi Frank, What a great question. sinc`e this amp is built of vintage parts, it would absolutely have been possible 50 years ago. Even the 6AL5 was around back then. But neither Tim nor I were. And yes, you make a lot of sense! Bob Carver
Q:  Dear Bob, I have a quick question, for my own information. I like the look of your pots. Are they a pot and or transformer combo that you made. My only guess is maybe McIntosh?? And if your quad wiring and DC Restorer are available to look at on a schematic. ( if your pats. are secure and filed of course). I am not going to copy it at all, just interested, of course! Thanks again, Frank E. Mar-19-09
A:  Hi '632, I don't remember where I got the pots....it was so long ago. Remember, I was old when Atlantas sank! I'll send you a schematic if you remind me after the auction, and you are welcome to copy it to build an amp if you wish. Thanks for writing, Bob Carver
Q:  Hi Bob How many dB of Global Feedback do you use in these amps? Is the feedback on the secondary of the OPT? Mar-19-09
A:  Hi 'Plies, Our amp uses the classical amount of 20 dB and if the output transformer is good enough to support a full twenty dB a switch on the front can change it to 11 db, a contemporary amount often used by modern amplifier designers. I prefer 20 dB. I prefer the full twenty if the output transformer is good enough to support it.
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

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1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
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#6 Posted: Saturday, August 15, 2009 11:12:09 PM(UTC)
 
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Rodney, thanks for posting those.  It actually brings tears to my eyes to read about so many audiophiles reacting to Bob's OBVIOUS love of this field!
 
 I'm hoping these pages are preserved for all to see for many years to come.  Having met Bob last year at CF '08, I feel like one of the luckiest folks on the planet.  I am SO HAPPY I got the opportunity to attend last year; too bad about this year.

ANY of you who can jump in the car & make to even a DAY of CarverFest '09 need to do it!!!

 
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#7 Posted: Saturday, October 31, 2009 12:56:19 PM(UTC)
 
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Question & Answer Answered On
Q:  What about the picture of the rear panel? Oct-27-09
A:  Well, I tried my best to get it up, but the help lady for eBay said that since I already had twelve pictures, I was stuck. So.....I'll use words. The back panel has a gold RCA input jack, two fuses, one for AC and one for the tube cathodes, a beefy line cord (see photo), a power switch, a flush mounted bias adjustment, four big terminal binding posts for the speaker, one black, three red, one ohm, four ohms, eight ohms. The back panel color is red, same as the rest of the chassis. Hope this helps, Bob Carver
Q:  Hi Bob, Lasareath here from the Polk Audio Forum. The Amps look so nice! Do you have any pictures of the rear panel? Thanks!!! Oct-27-09
A:  Hi Lasareath, yes I do; I just forgot to put it up with the other pictures. I'll see if I can add it at this late date - give me a couple of hours from now and check again. It's a great shot. Thanks for the reminder, and keep your fingers crossed that I can add it. Bob Carver
Q:  Bob, what preamplifier would you suggest for your amp? Oct-27-09
A:  Hi '871, I have several favorite vacuum tube preamplifiers, including the ones I designed. Just the same, for this discussion never mind those. Ahh, but for classic vintage tube units, my favorites are the Stu Hegeman designed Citation I, and the Tim de Paravicini designed EAR. Tim's has a beautiful as well as the quietest MC phono stage in the world, and Stu's masterpiece has wonderful tone controls and a spectacular sounding MM phono stage. If you have a moving coil cartridge and one of Tim's MC transformers, I would mate it with the Citation I and live forever in audio Heaven. Otherwise I would choose the EAR. When I was in hi-school, I had a job at a local Hi-Fidelity store called Seattle Radio Supply. We carried McIntosh, Marantz, Fisher, Scott, Citation, JBL and several others as well. I was allowed to take home as many as I wished, try them out and report my findings back to my boss. It was during that summer that I developed my preferences, and since EAR did not yet exist, my favorites became, in order, Citation, JBL, Marantz, Fisher, McIntosh. I was very young of course, but with all those superb units, I was truly able to stand on the shoulders of giants. Hope this helps, Bob Carver
Q:  Hello Mr. Carver. Is it possible to have these amplifiers converted over to 240v? If so, what would the cost be? Thank you for your time, Fritz Oct-25-09
A:  Hi Fritz, The cost is free, and yes it is possible. No problem at all, and the best part is that it can be done here in my laboratory or by you (assuming you know how to solder with a soldering iron). Or by a qualified technician. Good question, thanks for asking - ummm, I think I already answered this question. Oh well, twice never hurts. Warmest and best, Bob Carver
Q:  Hi Bob this is Eddie from Carverfest! I have to say you outdid yourself on this pair Bob they look sweet and I know they will sound as great too! Best wishes Eddie! Oct-25-09
A:  Hi Eddie! Thanks for the thumbs up - I found some vintage meters on eBay and a new paint color extremely close to the metallic burgundy cherry red I have had in my head for all these years. Thank all you guys for doing Carverfest - I sure had a ball. Bob Carver
Q:  Hi,,Do you ship t6o Thailand? Oct-23-09
A:  Hi '97. Yes I have the technology to ship these to Thailand. However I get help from Boeing, Airbus, and Overseas shipping inc. And of course the customs folks. Cost would be $516 dollars for both amplifiers. Hope this helps, Bob Carver
Q:  Hi, Bob. Do you build single end class A integrated amp with EL156/KT88/6550 (240VAC) compatible? How much would it cost with shipping to Singapore? Best regards John Oct-22-09
A:  Hi John. I don't specifically build a single ended unit, however this amplifier may easily be configured for single ended class A operation if desired. And with six KT88's, it would be the most majestic of all SE amplifiers! If you join the bidding and win my auction, I would be happy to make the conversion for you special. Of course you would still need a separate preamp. As for shipping and to Singapore, it would be $256 dollars for each amp. Hope this helps. Best wishes and warmest regards, Bob Carver.
Q:  Hello Bob, I just had to write and say "your amps just keep looking better", cool meters!!!, I like them. The best to you, "jay" Oct-21-09
A:  Hi Jay. Thanks for the accolade - helps make my day. I like the meters too - I found a stash of these vintage meters on eBay and thought WOW!would they ever look cool on a cherry red amplifier. Glad you agree. Bob
Q:  1st off I would like to say hello, and that it is really great seeing you getting back into tube amplifiers again. My first question: Is it possible to have these amplifiers wired for 240v if I were to win them? Second: would you mind explaining how your DC Restorer works please? Thank you for your time, and I look forward to hearing back from you. Warmest regards, Fritz Oct-21-09
A:  Hi Fritz. Yes, the unit can be wired for 240 volts - it has a dual winding power transformer for that purpose. It's a standard and easily made changeover. As for the DC restorer, first a bit of history: A class AB amplifier works by having the positive part of the waveform amplified by the top output tube, and the negative part by the bottom tube. In the case of a sine wave, the positive part is half a sine wave, or HAVERSINE, and similarly for the negative half. During the hand-off from positive HAVERSINE to negative HAVERSINE, that is, during the crossover period, the amplifier operates in class A. For the rest of the time it operates in class B - hence AB. Now the top tubes deliver a half sine wave signal to the output transformer, and this half sine wave possesses a DC value which depends on its amplitude. For lowest distortion, the drive signal on its grid should be a mirror image of the transformer drive signal and possess a corresponding DC value. It should be an identical haversine, differing only by the gain of the tube. And the two signals should be in perfect synchronism. Normal practise is to drive the grid with a standard sine wave that is symmetrical about the zero axis, so its DC value is zero. The DC restorer clamps the bottom half of the grid drive signal, thereby imparting a DC value to the grid and simultaneously providing a mirror image of the plate signal. The result is that both plate and grid have corresponding DC values. The best part is that idle power is cut to about one third, distortion to about one third, and finally, NO DC shift! The old way required enormous (by my standards) idle power in order to overcome or minimize these problems, never properly fixed the problems anyway, and has vexed designers since the very beginning. Often the output tubes were idled right at their maximum possible power rating, or even slightly beyond, often glowing cherry red. They got too hot, and didn't last long. WHEW! I hope you're still awake! Bob.
Q:  How in the world do you get over 300 watts out of such a small tube amp ??? Oct-20-09
A:  Hi 'i-o, Small? Small! It's big! I just knew someone would ask that, and here is the answer. This amplifier uses the mighty Silver Eagle KT88, and each pair is rated for 110 watts of audio output. Since the output stage is comprised of six tubes, we have 3 X 110 = 330 watts! Beyond possessing the raw power, the output transformer must have the correct turns ratio to deliver it all. The equal windings on this transformer allow a perfect match to either one or two ohms. And the mighty Silver Eagles do the rest. Great question, thanks for asking. Bob Carver
Q:  Can you ship to Italy? How much cost? Thanks Carlo Oct-20-09
A:  Hi Carlo, Yes indeed I can ship to Italy - I have the technology to do it - actually Boeing and Airbus do, and the cost is approximately $280.00. Thanks for asking and good luck.
Q:  Hello! For what sum are ready to sell at once? Best Regards Oct-20-09
A: 
Hello Nem'08, No amount, as we want this auction to run its clock down. Thanks for asking though, and if you join the bidding, I'll honestly root for you. Warmest and best regards, Bob Carver.
 
The above was from Bob's metered amps sold on 10/30/09
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

[b]On loan: C-16 preamp

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1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
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#8 Posted: Saturday, November 14, 2009 10:53:40 AM(UTC)
 
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Reading through all of this makes me darn proud of my Carver addiction.  all the high-falutin' knobs who sneer at my "mid-fi aspirations" for old Carver/Sunfire rigs should have copies of the above interviews stapled to their foreheads.   
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#9 Posted: Sunday, December 13, 2009 9:51:12 PM(UTC)
 
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What follows below is the Q&A section of Bob's tube amp auction that ended 12/13/09.  One of the questions contains a web address that Firefox flags as possibly hosting malware or is a forged site.  I suggest exercising caution should you wish to access that address.
 
The final sale price was $6975
 
Question & Answer Answered On
Q:  hi I am very interested in bidding on the amplifiers. How ever I wanted to check to make sure to would be okay to submit payment on wednesday......Pending I win the auction please let me know Thanks Robin Dec-13-09
A:  Hi Robin, No problem, no worries. Wednesday or even Thursday would be just fine. Hope this helps, Bob Carver
Q:  Hi Bob, I am currently am running B&W 800Ds with Audio Research REF5 and LAMM M1.2s REFs... How would this work in my setup (in place of the LAMMs)? Dec-13-09
A:  Hi '3xud, I'm assuming you're running your Lamm M1.2 on the bottom and your AR on top. If that's the case, then you have 120 solid state watts for the bass frequencies. More power would almost certainly give you better bass. Here's what I would try as an experiment (to find out). Temporarily reverse your amps with tubes on bottom and transistors on top. This will allow you to hear the characteristics of a tube amp with its impedance tracking ability for the low end. You won't be able to play it very loud, but that's okay for this experiment. Pay attention to the CHARACTER of the bass, and read my other answer below for a scientific discussion regarding the advantages of tube amps for bass PROVIDING (!) they possess high current drive capability. Bottom line - no pun intended - is that these amps would be better for your low end than the Lamm. And I could be wrong. Hope this helps, Bob Carver.
Q:  I was ready to bid on your auction, when a friend showed me this forum: http://ws1.chitose.melsa...community/eBayShowBlog/ People say bad things about you. Are you an honest seller? Dec-13-09
A:  Hi '1987, I tried to get to that forum, but could not - probably because I pushed a wrong button somewhere. Anyway, I'm sort of used to people saying bad things about me, even though I try to be a powerful force for good in our audio world. Oh well, at least there are lots who say good things about me; way more than the bad stuff, fortunately balancing the bad stuff all out. If I took it in, I'd drive myself crazy. So I just remember the good stuff and stay sane. And yes, I'm an honest seller; I'll even fix my amp free as long as I'm alive, even if it means replacing all the tubes. An easy promise - the chances of that are almost zero - everything would have to break all at once! If you want to test if it's really me here, ask me a question that only I would know the answer to. Like my dog's last name. See, it's really me! Warmest and best regards, Bob Carver
Q:  Dear Bob, sorry for asking question which is not regarding the current amp you are selling. :) I have your solid state Carver Research Lightstar Reference power amp from 1994. As there are several probs with the device, I want to ask if you could kindly send me a service manual. I could pay via paypal or any other option you would prefer. Many thanks in advance! Kind regards, Max (+7 495) 518-1870 Dec-13-09
A:  Hi Max, I would be happy to send you a schematic. I tried calling your number but could not reach you. Call Rita's at 425 530 9557, ask for Rita or Lisa, and I'll ask her to send you one. Also please send them your e-mail address. No charge, the schematic is free. Hope this helps, Bob Carver
Q:  Hi Bob, Ed again, I currently run a pair of Thiel CS5is through a pair of Krell KAS 2 class A mono blocks and am just wonder if your amps would be able give it the tube soundstage without sacrificing the bottom end? Thanks. Dec-13-09
A:  Hi Ed, For a variety of technical reasons, tube amps are able to deliver a beautiful and enveloping soundstage like no other. They also will have a bottom end that's more powerful than a solid state amp IF - and here's the caveat - they ALSO have a lot of current drive capability. Now, all cone based loudspeakers (including your Thiel's), have an impedance rise in the bottom end, and a tube amplifier can easily follow this rise because of its internal generator none-zero output impedance. A transistor amp usually has an internal generator impedance that approaches zero, so its drive can't follow that impedance rise. So far so good. But what goes wrong with all this in the real world is that tube amps almost always becomes current starved when trying to deliver intense low bass. That's where solid-state amps have an advantage, usually outweighing the intrinsic bass superiority of tube amps. The only way I know of to have my cake and eat it too ( besides forgetting some of the lessons my mother taught me), is to design a tube amp that has enormous current reserves. I did it on purpose with this amp by using twelve mighty KT88's in the output section, by operating their screen (grid #2) connections from a separate high voltage power source, and finally, by use of a DC restorer. This amp can deliver over 24 amperes and 300 watts into one ohm. With speech and music waveforms, that number becomes a whopping 450 watts into FOUR ohms with all the current we could rationally want. Better than all but the biggest solid state amps. Have your cake and eat it too - tube amp soundstage with low frequency bottom end impact and slam. Great question, Bob Carver
Q:  Hi Bob –Its straylight, I bought the 4th pair amps in Dec 2008, item #180315426456 including Citation I preamp that you rewired to create a moving coil input for me! -one of a kind! Bob, shortly after our last call I was diagnosed with a life threatening disease and although my prospects for surgery in January look good there are no guaranties in this life. It also makes having listened to your 180 mono amps over the past year all the more special. Your amps have been a true inspiration to me and your auctions are the best educational tool on ebay! After you and I leave the ‘stage of life’ your amps will go on to inspire a whole new generation to say "what a wonderful soundstage", "what was Bob thinking when he designed these?" Since we may never know exactly it only depends the mystery & charm of these wonderous audio creations -the best I've ever heard in a lifetime! Thnks for bringing these amps into the world...it has helped me focus on what's important in the remainder of my life Dec-12-09
A:  Hi Straylight - Your focus on the important things is going to last a long, long time to come; there are no early outs for you or for me. Not yet. You'll see. I'm calling you after January so I can watch over you and thank you from the bottom of my heart for your inspiring message! Bob
Q:  Mr. Carver...I am listening at this very moment to a Carver 390t tube CD player, and an M400a 'cube' running a pair of Maggie MG1c's....and LOVING THE SOUND! I've been a fan since acquiring the M400's a few years ago. I need though to get enough juice for a pair of MG3a's and I previously used a pair of the M400a's bridged to mono but soundstage collapsed beyond my tastes when bridged. ***Will your new amps have similar characteristics?*** The Maggies reveal everything and need plenty of power. 500wpc is not TOO much if it's clean. Dec-11-09
A:  Hi 'st, Oh man, you are making my day! It's fun to hear about your M400 still making music after all these years! As for these 180's, since they are tube amps and have an output transformer with taps that will step up their output voltage, bridging them would be redundant and unnecessary. Regarding their soundstage presentation - that's one of the things big tube amps do best, building a soundstage, and with beautiful imaging inside that big soundstage. Great comments, thanks for writing. Bob Carver
Q:  Hello Bob Could you email me the dimensions of the amps please as i have two amp stands and would like to know if your amps would fit them. Could these amps be picked in person as i live in Vancouver B.C. Thank-you Ken Dec-10-09
A:  Hi Ken, 12 1/4" wide X 14" deep X 7" high. Plus the height of the feet = 0.5". Plus the terminals on the back stick out ~ 0.8". I spent my first year in grad school at the UBC right there in Vancouver, and have many fond memories of my time there. I'll go you one better - I would love to drive around my old campus from so long ago, so if you win our auction, I'll deliver them myself, help set them up, take you to dinner and talk into the night about tube amps. Thanks for writing, Bob Carver
Q:  Hi Mr. Carver, It's both a pleasure and an honor. I wish I had a disposable income at this point that enabled me to snap up this last pair of amps, but I do not - short of winning the lottery :) Have you made any progress in cloning those unique transformers, or is this the last pair of amps that will feature these wonderful characteristics? Of course, I ask because I am also an Apogee owner that wants a tube amp that can "deliver the goods" with whatever Apogee model I choose. I have owned Scintillas, but sold them due to economic considerations, and now own a pair of hybrid Centaurs. Thanks for your time. rube Dec-10-09
A:  Hi Rube, Oh well, maybe you WILL win the lottery, or the Irish Sweepstakes - I'll be keeping my fingers crossed. As for output transformer progress, I've been too busy of late to start the project as clonemaster for these transformers, but I will start soon. The biggest Apogees were the most difficult to drive, and I must commend Jason Bloom for designing them HIS way for the best possible sound, allowing the impedance to fall wherever it needed to be to get the perfection he wanted. That takes a great deal of courage in the face of practical issues, such as getting the speaker to work with normal amplifiers. I too am an Apogee lover - that's exactly why I had to make this tube amp operate into one ohm. Thanks for writing, Bob Carver
Q:  Hello Mr Carver! Beautiful amps! And I have three different pairs of Apogees, among thme the Scintillas; that that I’m sure would love to be powered by these babies. I am however a european resident. Can they be rewired for 220V? Can you ship to Europe? Best regards, J Dec-10-09
A:  These amps do LOVE Scintillas, and they can easily be wired for 220V, as they have a split primary designed just for that purpose. And yes, I can ship to Europe by using technology from the Cross Oceanic Shipping company, Boeing, or Airbus. Bob Carver.
Q:  Hi Bob, Are these only wired for 110v only? Does the transformer allow for a 220/240v tap? Thanks Regards Ed Dec-10-09
A:  Hi Ed, The power transformer has a split primary, allowing it to be wired for 110/120 or 220/240. The changeover is easily done by you, me, or a qualified technician. Thanks for asking, Bob Carver
Q:  Hello Mr. Carver, it's a pleasure to see another one of your beautiful amps. Would you be so kind as to email me a pic of the rear and a schematic? I don't want to assume all the large brown caps are coupling caps. Viewing the minimalistic design, I feel like a curious kitten. I'd also like to know the dimensions. In regards to specs, I've had input impedance issues with a Cary product that resulted in poor input sensitivity. What would you recommend for these amps? My tube preamp specs are Gain= 18.5db, Output Impedance= 40 ohms, and Max output= 40vrms. Hopefully my preamp will like these amps, and I'll be warming up my music room and spinning my vinyl with these. Looking forward to your answers. Best Regards, Werner. Dec-09-09
A:  Hi 'samx, I would be happy to send you a picture and a schematic. I need your e-mail address; please send it to me bob.sunfire@gmail.com On another note, the input impedance of this amp is 100K ,and its gain is 30dB. That means it is perfect for your preamp, as the loss would be 0.0035 dB - nothing! And with 18.5 dB gain from your preamp, you will have all the drive you could ever hope to have. Thanks for the questions, Bob Carver
Q:  Are you using a negative feedback to stabilize the DC? I notice you have this in some nice wood chassis or maybe it is metal. I found this stuff called MuMetal. It is expensive, but I use it in high end guitars and amps for use on the stage where lighting and other stuff wreaks havoc with EMF and 60 Hz hum. I would really like to know how you have balanced the DC on this. What did you use as output transformers? Are they old vintage or custom wound? I find some of the older stuff is not consistent. Key word is SOME. 1 ohm tap!?!?! I see that very rarely, and not usually on tube amps. The sound through a 1 ohm speaker(s) is very detailed and sweet. I wound guitar pickups custom on both a couple home made hand machines, lead screw guided machines, and the famous Leesona (POS). I am looking into financing a CNC cutter for core laminates and a Chinese made CNC lead screw machine that supposedly will handle up to #6 AWG. I am super curious. Contact me. God bless you 2! Dec-09-09
A:  Hi 'moeddie again, Since this tube amp has an output transformer, and all its feedback is taken from the secondary winding, there can be no DC feedback. That's because a DC signal cannot be supported at all by a transformer. It would have to be infinite in size - that's bigger than the universe is large - 15 billion light years to its visible edge. Though this output transformer is massive, it's not quite that massive! The output transformers are very vintage, not custom wound, and each possesses a split bifilar wound secondary. Hence the one ohm tap, which emerges quite naturally by wiring the secondary half up, half down. Viola' - one ohm and 305 watts, thanks to the DC restorer and six KT88's. As for Mu-Metal, it's great stuff, expensive as you said, and normally restricted to very small amounts where low level signals need to be well shielded - as in guitar and vinyl phono pickups. Hope this helps, Bob Carver
Q:  I do work for a man who owns a used car dealership that deals in high end cars. They are status symbols but they go down in value faster that they can go down the road. He has a small museum of old guitars and amps in an old courthouse in upstate NY. I do lots of repairs and try like anything to use Astron caps, or whatever was original, or just use good stuff and keep the old parts (always keep the old parts in a bag). I would like more information on how you stabilize the DC from drift and shift as I call it. Either it is drifting around, or sometimes it will just shift from a reference point suddenly. My utility power quality is perhaps the worst in any large urban setting. We had 62 MPH top wind gust at 23:07 Mon night. The top recorded was 74 MPH. 250,000 people lost power. I have had 83 interruptions since 21:30 Mon. There are spikes, sag, noise, and even freq drift of >10%. I run through a UPS and iso trans just so I can work. I'd love more info on this. Dec-09-09
A:  Hi Satchmo, Well, I hope these amps don't go down in value as they get older. I hope they become classics down the road and GROW in value because they sound great, as well as becoming (in time) vintage. Now that I think about it, they already are vintage because of all the vintage parts inside. The DC shift is eliminated through the use of several things: one, about ten times more energy storage than vintage classics used, two, balanced long-tailed voltage amplifiers from the input stage through the output stage, and three, the use of a 6AL5 DC restorer to restore the lost DC value of the signal as it propagates from input to output. These three things combine to reduce idle power dissipation, harmonic and IM distortion, and best of all, "drift and shift". With this amp you won't need a UPS and an isolation transformer at all! Bob Carver
Q:  Any pictures of the rear panel of the unit??? Regards, Warren Galliano Dec-09-09
A:  Hi 'ianno, I DO have a nice picture of the rear panel, but I don't know how to post it here without starting my auction over. That's because I already have the picture limit posted, according to the eBay help line. Looks as if I goofed up at the start of this auction. What's your e-mail address and I'll e-mail the picture to you. Bob Carver
Q:  Hi Bob, I spoke with you last year about your new amp design. You had offered to shoot me some information on the design schematics. I never had a chance to follow up with you and I lost track of your ebay name. I have built a couple of amps this year based on the Williamson design using KT66's with 6CG7 drivers and Heathkit iron. Not a bad sound at all to them! I would love to get a look at your new amp circuits if it is still Ok with you. Thank you for helping me out if you can! Frank Erdin New Jersey Dec-09-09
A:  Hi Frank, There is nothing more fun than building tube amps, and the Williamson circuit is a true classic that would bring lots of pride in a personal home built unit. I'd be glad to e-mail you a schematic, just give me your e-mail address and I'll send it off to you this evening. Bob Carver
Q:  Hi Bob, can you tell us a little about your Scintilla speakers? Original ribbons? Modifications? Did you own other Apogees as well? Thanks from a former Carver amp/preamp owner from the past as well as a current Scintilla owner. Dec-09-09
A:  Hi 'ale, I bought them many years ago from a Carver dealer here in Seattle. They are the original ribbons, with no modifications, and yes, I owned several other smaller Apogees around the same time as I owned these. I can clearly remember thinking - "I am truly in the presence of a great loudspeaker, maybe even the greatest." - when I first listened to the Scintilla. On another note, I hope your Carver amp found a happy home, even if it's no longer driving Apogees. Bob Carver
Q:  There's always more transformers somewhere and fabulous things to design! Dec-09-09
A:  Absolutely! But sometimes with a hitch. I bought these output transformers long ago when I was a freshman in college from a surplus place in Los Angeles. I've finally gotten around to looking inside one of them - my last one - and it is built way to expensively and beautifully to be a commercial transformer; it is clearly a military spec transformer, probably built in a time when output transformer design was far more artful than it is today. There is none that can compare, as far as I know, and I'm not exaggerating. As I see it, my job now is to figure out how it was built in every detail. Then I can clone it. Bob Carver
Q:  Hello Bob Thought I would use this way to say g'day to an unlikely Ap' owner as I don't have an email address for you! That valve amp looks FANTASTIC!! Bet it could solve a few of my clients "problems" ;) Take care - Graz info@apogeeacoustics.com Dec-09-09
A:  Hello Graz, Thanks for the accolades. I think they look great too, but then again I designed 'em so I was prejudiced to start with. Still, I must say they operate my Apogees beautifully; it's that one ohm tap and the six mighty KT88's. My e-mail is bob.sunfire@gmail.com Bob Carver
Q:  how many pairs have you made and how many more can you make like these , these look so nice BOB , good job ,very classy thanks kevin Dec-09-09
A:  Hi '739, I have not kept track all that well, however I think five pairs to date and auctioned on eBay. I'm out of these great output transformers now(except for one lone unit), so I cannot build any more amplifiers like these unless I clone the transformers. However I do have my old transformer winding machine left over from my Silver Seven days, and if I get lucky enough I'll be able to use it and make a close facsimile. Thanks for the appreciation Kevin, it took me some time to find just the right color - it came from an old '56 Chevy I had as a teenager. Metallic strawberry burgundy. Bob Carver

Q:  Hi Bob, How would these compare with silver 7's? Dec-07-09
A:  Hi 'rc, That's like asking "Who do you love the most?" I love them all - each has a distinct and different personality, unique and beautiful, but different. Children and amplifiers share SOME things in common. My Silver 7's are not to be believed, they are so good. - I didn't say it - many others did though, and these new mono- block amps are designed with Tim's and my latest thinking. I love them both!
Q:  Good Morning Bob, I'll change my name to Skip if you want to send those "Babies" to Oklahoma, serously tho, the new color scheme and the meters make me want to stand up and take notice, you have another winning pair there. "jay" Dec-07-09
A:  Hi 'music, If you changed your name to Skip, the amps might just skip right past Oklahoma on their way to audio Nirvana somewhere beyond Beethoven's 9th. But then again, perhaps not. Bob Carver
Q:  Wow! Sounds like some real schmoes out there just using your photos and such. Knowing Ebay I bet they do little about it. Dang! Dec-04-09
A:  Hi 'tube meister, It's extremely frustrating - I have tried repeatedly to put an end to it but found it impossible so far. In all fairness to eBay, I don't think they can do much either. So I'm left with posting WARNINGS wherever I can. If any reader knows of anyone being cheated by this fraudulent offer, please let me know right here on the eBay forum. If it occurs in this country, I have a good chance of stopping it and probably even getting the victim's money back. Bob Carver
 
 
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

[b]On loan: C-16 preamp

Blue Mouth Promotions LLC Where the music matters most!
1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
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#10 Posted: Thursday, December 31, 2009 11:48:32 AM(UTC)
 
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This is a little bit out of sequence unless Rich can re-order the posts in this list.  The following is the Q&A from the second pair of amps sold.  Of particular note is these are the Stu Hegemam/Bob Carver design and have slightly different specs.  Dates for this posting can be found at the end of each question.  I do not know if this was the entire Q&A because sometimes they ran into 2 or more pages and this is not a direct HTML copy, but it belongs here for posterity anyway.   It was generously posted in the Dark Tower by the owner.  Now, if only we could find the Q&A from the very first auction........
 
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Q: Hi Bob, I am also like many others having really hard time believing that it is you. Anyways, my question to you is are you also planning on building matching new tube preamps to go along with these? Please let me know. Thanks, Jul-02-08
A: It's me alright. And no, I don't have plans to make a new tube preamp. A Sunfire or Citation I preamp would do nicely though. Good question! Bob Carver
Q: Hi Bob, Can you please indicate the input options and the input impedence. Also the sensitivity input voltage for full output. The damping factor at 4 ohms speaker load. THD and IMD at full output. Thanks, James Jul-02-08
A: Since gain = 30 dB,sensitivity for 205 watts @8 ohms = 1.28 volts. My favorite Zout = 0.425 @ 4 ohms,yielding a damping factor of 9.41, THD = 0.15%, IMD = 0.5%, Zin = 100,000 ohms. Since this is a basic amp, input options are limited only by our imaginations. Bob Carver
Q: Dear Bob, Are you are the man who designed the phase linear amps? I want your amps but living in Hong Kong, can I have chance to buy it? many thanks, Alex Jun-30-08
A: Hi Alex, Yes, I am the one who designed the Phase Linear amplifiers. And yes, of course you have a chance to buy it. Warmest and best regards, Bob Carver
Q: Hello Bob; Other than to clean your closet, why is Bob Carver, one of this generations great audio designers, selling onesies (single units)? Thank you! Jun-30-08
A: I really don't know why. It's just that whenever I look at my lifetime collection of vintage parts, I feel like building an amplifier. I don't know why, I just do.
Q: Hey Bob. You forgot to mention the split primary on the power tranny. Also, what about the weight and power specs? Thanks, Joe Jun-29-08
A: Oops! I forgot. Correction: This amplifier is rated at 205 watts, not 180 watts. That's because the GE 6550's are remarkably efficient. The amps weigh more than 42 pounds each - 44 lbs each. And they possess 120/240 volts, 50/60 Hz AC line capability. I used some older text and failed to update. The remaining specs are accurate. Please accept my deepest apologies. Bob Carver
Q: Hi Bob, You just never know who you'll run into on eBay. How kool is this, the great Bob Carver, designer of audio equipment extrodinaire! One question Bob, does Bill Gates ever invite you over for a cookout or to play 18 holes? Take care and keep designing all that great audio equipment. Regards, Ted Moyer Jun-29-08
A: I wish, except I'd rather design amplifiers than play golf. Thanks Ted for the extraordinaire! You made my day! Bob Carver
Q: Dear Bob, Beautiful amps, again! I am very curious about your circuit -- Is this similar to a Citation V, or more like a Lafayette 550 with a triode plate follower to provide the inverted signal? Which video pentode (or pentode+triode?) has been used? Thanks! And, best of luck with the auction. Jun-29-08
A: This inverter is more like the Lafayette 550 anode follower. I like this inverter because it is immune to tube parameter shifts. In my opinion, The Lafayette 550 was his very best and most inspired work. Complex but brilliant. I'm using a 6AW8 video pentode plus triode. Thanks for your comments and for asking. Bob Carver
Q: I thought these were designed by Carver and DePavaracini? When did this change? Jun-28-08
A: These are completely different amplifiers. The ones designed by Tim and me were auctioned two weeks ago. I'm glad you asked because I think others may miss that point as well. Bob Carver
Main System:180 Tube Monoblocks, ALS Hybrid Plats, Oppo BDP-93, TD-1400, TX-11b, Sunfire Classic Vacuum Tube Control Center, C-9 Sonic Hologram Generator, Dual CS 505-1 turntable, Streaming iTunes through an Apple TV to a Cambridge Audio DacMagic 100

Temp system: C-1, M500 MkII

[b]On loan: C-16 preamp

Blue Mouth Promotions LLC Where the music matters most!
1 user thanked weitrhino for this useful post.
RichP714 on 4/22/2010(UTC)
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