Questions for Bob Carver. Ask here.

[Ar9Jim 6,501]

I'll be talking to Bob in the next couple days. I'm writing down questions.

Feel free to ask your question of the week about anything, past, present or future.

Controversial topics are encouraged. Crimson 275 questions are welcome. Ram 285 questions are welcome.

Questions of science vs audio beliefs, or any topic you would like a short, straight, honest answer about, ask here.

Don't be shy!

 

Enjoy!

 

UPDATE: Now question of the week is a regular weekly event.. Post questions before Thursday and have an answer on the weekend.. Our hobby is polarized and being taken advantage of with beliefs at both extremes at the hobbies expense. Bob Carver has been a maverick in this industry for many decades by simple telling the truth as filtered through his physics and mathematics education, combined with decades of study and experimentation. Bob is great at explaining and is a wonderful teacher. 

 

Edited November 23, 2023 by Ar9Jim

[PhilDent 1,827]

Maybe I missed it, but did you ask him why we should buy tube amps when we are satisfied with our solid state Carver gear?

[wrf 4,395]

Inverted amplifiers such as the M-400 and M-500 are an interesting idea.  Yet it didn't really catch on.  In fact, I can't find any inverted amplifiers today.

 

From your perspective, why have inverted amplifiers faded away?

[Ar9Jim 6,501]

4 hours ago, PhilDent said:

Maybe I missed it, but did you ask him why we should buy tube amps when we are satisfied with our solid state Carver gear?

It's a subjective question. You may be happy with solid state Carver gear because it has a tube amp like transfer function by design. Being happy with it, you have no reason to buy a tube amp.

 

Has Bob improved sonic performance in the last 25 or 30 years? Of course he has, but the solid state will still measure better than a tube amp, so objectively there is no reason to buy a tube amp. You have to compare Bobs tube amps for yourself to determine the sonic value to you. 

 

That's why we have the Carver Amp Challenge. We don't expect anyone to take our word for it. We don't deal in snake oil at one extreme in the hobby or chasing the best numbers at the expense of sound quality priorities, to satisfy the best measurements sounds best believers. If best measurements are the goal, solid state is the way to go. People have to experience audio. Then the choice is clear. It just happens to land in our favor 98% of the time. I'll ask Bob what he thinks, but this reflects our mission statement. Great question.

Edited November 18, 2023 by Ar9Jim

[Ar9Jim 6,501]

Bob,

In the Crimson 275 why did you use your Edcor EM0946 output transformers that you had designed years earlier. They are labeled only 15 watts. Why were those chosen?

 

The owners adore the Crimson 275s and no one can deny that they sound great. How and why are they built so light? What were the design goals?

 

 

 

 

 

Edited November 18, 2023 by Ar9Jim

[Kurt 2,215]

Question for Bob: Of all the products he's designed over the years-  What is his favorite and his least favorite?

[Ar9Jim 6,501]

14 hours ago, PhilDent said:

Maybe I missed it, but did you ask him why we should buy tube amps when we are satisfied with our solid state Carver gear?

A) Bob- For myself I just like the tubes. Listening to music at night with the tubes glowing is just special.

[Ar9Jim 6,501]

13 hours ago, wrf said:

Inverted amplifiers such as the M-400 and M-500 are an interesting idea.  Yet it didn't really catch on.  In fact, I can't find any inverted amplifiers today.

 

From your perspective, why have inverted amplifiers faded away?

A) Bob - I think it has to do with people liking larger transformers. With the inverting design you can get the same power from a transformer about 1/2 the size, saving weight and making the products more affordable. It's been successful for me in the market.

Edited November 19, 2023 by Ar9Jim

[Ar9Jim 6,501]

1 hour ago, Kurt said:

Question for Bob: Of all the products he's designed over the years-  What is his favorite and his least favorite?

The Phase 700. It made more power than anyone else and it put me on the map. Before that it was Bob who? Least favorite- I love them all like children.

Edited November 18, 2023 by Ar9Jim

[Ar9Jim 6,501]

Bob,

Q) Why do tube amps have much smaller power supply caps than typical solid state?

 

A) Bob - Well, they are smaller in capacitance but not energy storage. Its about energy storage. Remember .Work(W)=1/2Capacitance(C)Voltage(V)2. Tube amplifiers have very high voltage and the high voltage capacitors store a lot of energy.

 

 

Edited November 18, 2023 by Ar9Jim

[Kurt 2,215]

1 hour ago, Ar9Jim said:

The Phase 700. It made more power than anyone else and it put me on the map. Before that it was Bob who? Least favorite- I love them all like children.

Thank you, Jim!.... and Bob!

[Ar9Jim 6,501]

7 hours ago, Ar9Jim said:

Bob,

In the Crimson 275 why did you use your Edcor EM0946 output transformers that you had designed years earlier. They are labeled only 15 watts. Why were those chosen?

 

The owners adore the Crimson 275s and no one can deny that they sound great. How and why are they built so light? What were the design goals?

 

 

 

 

 

A) Bob - The Crimson 275 is designed to be light, powerful and affordable. Work(W)=1/2Capacitance(C)Voltage(V)2. Remember the voltage is squared. To increase power 9x requires a voltage increase of 1/3. With this high voltage design, I chose my EM0946 output transformer designed more than a decade ago. They provide the amplifier / speaker interface qualities I prefer at the best value. The 275 makes a lot of power. Does any other tube amp make that much power at 19lbs.?

 

Q) On the bench in Rockford the 275s make 75-80 watts at 1KHz into 8 ohm resistors. Frequency response test at full power showed some roll-off and some anomalies below about 50 Hz.. We changed the power spec to 75w @1KHz like tube amps are typically specified as you instructed when we started the new company. The full power to 20Hz spec was corrected.

 

A) Very good. Designers should write specs, never marketing or salesmen. When running loudspeakers and measuring, those anomalies don't show up. The frequency response is flat. The power response curve closely matches the spectral power distribution of music. It's one of my best designs.

Edited November 18, 2023 by Ar9Jim

[Ar9Jim 6,501]

A new week ahead. Ask your question before 11-24 for the 11-26 reply from Bob. Enjoy!

[Ar9Jim 6,501]

Question:

J. Clark - There is a big difference in bench test numbers between the RAM 285 and Crimson 275. The 285 weighs 56lbs and the 275 weighs 19lbs. Can you explain the different approaches and design goals please.

 

A) Bob - Sure. With the 275 I spent many months listening and applying many decades of research and what I've learned about making an amp sound best. I wanted the Crimson 275 to sound great while being light, powerful and affordable. The roll-off you noticed is by design it starts at about 60Hz actually. This kept the weight and cost down, so more people could afford it. Frequency response needs to be flat, but power response does not. The spectral power distribution of music is not flat and there is not as much power requirement at either end of the spectrum. At the high end no tweeter in the world could take 75 watts at 20KHz. 

I designed the Crimson 275 to sound the best at the best value and let the bench test numbers land where they may. 

 

 J. Clark - That makes sense. If we turn off the amp but leave a sub running that's crossover around 50Hz, most times it's not actually doing much.

 

Bob - Exactly. The majority of full range speakers won't go that low and people use subwoofers.

 

J. Clark - The specs were written like boilerplate solid state specs and caused a commotion as we have talked about before, but it's good to get it on the record.

 

Bob - Yeah, I tried to retire and just walked away for a couple years. I didn't pay much attention and you have had a tough job to deal with because of it.

 

J. Clark - No doubt. I promise you sales or marketing will never write specs on my watch. What a mess.

 

Bob - The RAM 285 is designed to a higher price point. At this price point and selling direct things get exciting. I've designed everything I have learned at the bench and decades of study into what sounds good into the RAM 285 without concern for weight or cost. The 285 in a legacy product. I really can't imagine how anyone could design a better sounding amplifier than the RAM 285, I really can't.

 

J. Clark - I can't either Bob. At any price. I'll bet we never lose Carver Amp Challenge. The 285 is really special. 

Edited November 20, 2023 by Ar9Jim

[Ar9Jim 6,501]

On 11/17/2023 at 5:16 PM, Ar9Jim said:

I'll be talking to Bob in the next couple days. I'm writing down questions.

Feel free to ask your question of the week about anything, past, present or future.

Controversial topics are encouraged. Crimson 275 questions are welcome. Ram 285 questions are welcome.

Questions of science vs audio beliefs, or any topic you would like a short, straight, honest answer about, ask here.

Don't be shy!

 

Enjoy!

 

UPDATE: Now question of the week is a regular weekly event.. Post questions before Thursday and have an answer on the weekend.. Our hobby is polarized and being taken advantage of with beliefs at both extremes at the hobbies expense. Bob Carver has been a maverick in this industry for many decades by simple telling the truth as filtered through his physics and mathematics education, combined with decades of study and experimentation. Bob is great at explaining and is a wonderful teacher. 

UPDATE.

[Ar9Jim 6,501]

Thanks for the questions.

 

Edited November 23, 2023 by Ar9Jim

[Kurt 2,215]

shoot, I had more questions... I just didn't want to be the only one asking them.... If you get this routine back up and running, here are a few more questions I had....  

 

1. Does Bob benchmark other brands/other amplifier builders?  Are there any current makers, besides Carver of course, who make nice sounding gear?  Or, who would Bob consider his chief competition?

 

2. (I happen to really like vintage Infinity speakers.) Did Bob ever do any work with Arnie Nudell?  Does he have any stories/anecdotes from back in the day?

 

3. What is Bob's favorite music to listen to when he's dialing in an amp?  What is his "test" music of choice?

[radtraveller 266]

If “straight line” with fewest parts between source and speaker is supposed to be better, why all the circuitry and doodahs in a pre-amp?  Just a gain, impedance match and call it the “best ever made”?  (Would probably measure really well)
Don’t forget your unobtainium power cord sheathed with magicanium maybe aSignal Projects Golden Sequence ($4,675 USD),

Furutech Lineflux and Speakerflux (from $2,650 and $3,650 USD pr) and a who can go without a couple of Skogrand Beethoven USB ($11,000 USD) for that vintage mp3 player.

Edited November 22, 2023 by radtraveller

[jeffs 3,056]

2 hours ago, radtraveller said:

 Just a gain, impedance match and call it the “best ever made”?

If you use a C-1 in it's simplest form using a line input with no switches engaged, that's pretty much what you get ..... except .....

 

The problem with this circuit is the way balance is implemented. It's really less than ideal. If you leave tone control out, the input is essentially connected to  the left side of R335.

The preamp input impedance becomes R335+R336+ (20K volume in parallel with 25k( 1/2 of the balance pot)= 13.42K. Already somewhat low but acceptable.

If you turn the balance pot all the way to one side, the volume pot is shorted to GND on the other side. The input impedance on the opposite side becomes R335+R336= 2.32K .... So the input impedance is dependent on balance pot position.

 

Otherwise the C-1 simplest path is more-or-less just a volume pot followed by a simple gain circuit (18.6dB).

 

 

Edited November 22, 2023 by jeffs

[Ar9Jim 6,501]

13 hours ago, jeffs said:

If you use a C-1 in it's simplest form using a line input with no switches engaged, that's pretty much what you get ..... except .....

 

The problem with this circuit is the way balance is implemented. It's really less than ideal. If you leave tone control out, the input is essentially connected to  the left side of R335.

The preamp input impedance becomes R335+R336+ (20K volume in parallel with 25k( 1/2 of the balance pot)= 13.42K. Already somewhat low but acceptable.

If you turn the balance pot all the way to one side, the volume pot is shorted to GND on the other side. The input impedance on the opposite side becomes R335+R336= 2.32K .... So the input impedance is dependent on balance pot position.

 

Otherwise the C-1 simplest path is more-or-less just a volume pot followed by a simple gain circuit (18.6dB).

 

 

After that the straightest path is a "passive preamp" It's a conflicted word but often the description. Steve McCormick ? IIRC . Made some really nice passives under Mod Squad brand. There is a purity about them but they are a bit lifeless. The construction of the Mod Squad I tried was excellent. That's a straight wire without gain.

[4krow 5,863]

IME, passives are called 'passive' for a reason. When I suggested adding a buffer to a passive that he built for me 30 years ago, at that time he shrugged his shoulders. Then he did it and was very impressed with the result. For whatever reason in that case expecting a good result directly from a CD player to Forte' 3 power amp was as mentioned above, lifeless. I am sure that not all buffers are the same. The least impressive was one that I built years ago using a 6SN7 tube. Suffice it to say that I suspect that it had far more to do with circuit design than choice of tubes used.

[Ar9Jim 6,501]

Passive and preamp are often used together.. If it's passive, is it a preamp? That's the conflicted word, imho.. It's like passive active. Seems a bit conflicted. I've only used the Mod Squad with a 2 v DAC and CD player feeding the passive. Preamp with gain was better in that set-up.

 

[Ar9Jim 6,501]

This makes a good question for Bob.

Why did feeding a passive preamp with line level (2v) source, seem less dynamic than adding a preamp with gain outputting less than 2v output during use.. 2 volts would be plenty of voltage to clip the amplifier. Was it more voltage potential or headroom that made the improvement? Impedance match issue? I read about passives with buffers being better, so the impedance doesn't change with volume pot position.

Edited November 23, 2023 by Ar9Jim

[Dennis47 904]

Jim,

 

I have an off-the-wall question for Bob:

What does your top twenty music playlist look like and what source medium do you prefer?

 

Thanks,

Dennis