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New member from East Central Illinois


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Greetings!

 

I recently learned about this site while browsing YouTube videos relating to repair/restoration of vintage Carver amplifiers.

 

I myself am a "vintage" electronic engineer and former owner of an audio retail store (August Systems) and an electronic repair shop (Audio-Video Service Center) located in East Central Illinois. During my retail career I was a Carver dealer and authorized service center. Those parts of my career began in the 1970's and extended into the late 1990's. These day's I'm semi-retired but still restoring/repairing vintage audio gear for my friends and family. This includes Carver and Phase Linear products. My experience is that nearly all vintage Carver/ Phase Linear products can be restored and enjoyed for many years.

 

As a Carversite member I hope to be able to provide assistance to those who are repairing/restoring Carver gear.

 

Here's my personal contribution to Carver history:

 

Only two products were available during the very first year of the "Carver" brand name: These were the C-4000 "sonic holography" preamp and its companion C-500 power amplifier. These items were updated/modernized versions of Bob Carver's previous Phase-Linear 4000 preamp and 400 power amplifier. They looked and sounded great. But except for the addition of the "sonic holography" feature to the C-4000, their circuit designs were still fairly conventional. 

 

The real excitement happened about a year later with the initial release of Bob Carver's M-400 "cube" power amplifier: 200Wpc in an unbelievably small and lightweight box. As a young audio engineer I was entranced by the brilliant circuit design of the M-400. It contained two ingenious (but extremely logical) improvements compared to traditional solid-state power amplifiers: 

 

1) The "magnetic field" power supply circuit:

  • The primary winding of the main power transformer was supplied by an active triac circuit which reduced the conduction angle from full cycles of incoming mains AC to much shorter "pulses" controlled by the triac.
  • Under the "no-signal" condition the pulses of AC feeding the power transformer primary were  only a few msec in duration.
  • As more power was demanded the triac conduction angle increased to maintain a regulated DC output voltage from the secondaries of the power transformer.
  • Both the primary and secondary windings of the main power transformer required a much lower inductance compared to a "standard" 60Hz power transformer.
  • This reduced the size/weight of the "magnetic field" power transformer to about 1/3 of a "conventional" 60Hz power transformer with the same ratings.

 

2) The 3-step "commutating" DC +/- rail voltages applied to the audio output stage.

  • This greatly increases the power efficiency of the amplifier when driving  loudspeakers with typical music audio signals.
  • Audio signals have a very high "peak-to-average" power ratio. This can be as high as 20dB. The average power output is often <10W, but when a musical peak comes along >200W will be required for a few msec.
  • Traditional solid-state power amplifiers apply the full B+ voltage (+/-75V DC for 200Wpc) at all times to the collectors of the output transistors. But during "normal" listening < 20% of this voltage and power is being fed into the loudspeakers. The remainder is dissipated in the form of heat by the output transistors. This is why conventional high-power solid-state amplifiers require such massive heatsinks.  
  • In contrast the Carver M-400 has additional +/-25V and  +/-50V DC power supply rails. A system of diodes and "commutating" transistors varies the collector voltage applied to the main output stage from +/-25V up to the full +/-75V, rising just high enough to prevent clipping.
  • Most of the time, while listening to music, only the +/-25V power supplies are active. This reduces output transistor power dissipation of  by a factor of about 8 times. In other words, much less power is wasted in the form of heat.
  • This is why the M-400 doesn't require large heatsinks for the output transistors: The aluminum case itself provides a sufficient heatsink surface area.

 

Each later model Carver amplifier after the M-400  improved the efficiency and audio quality. To the best of my knowledge nearly all of Carver's later solid-state amplifier designs were improved and scaled-up versions of the circuit design first introduced in the M-400.

 

Best regards,  Elecdonia

 

Edited by Elecdonia
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Welcome.jpg

 

It's always great when someone who was involved with Carver, back in the day, joins - especially when they are active in looking after gear, still.  You'l find lots of kindred spirits, here, along with a mixed bag of other nutcases, like myself.  All of us share a love for great audio, with a particular interest in the creations of Bob Carver.

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Hello Elecdonia, and welcome to thecarversite.com. We're glad you're hear. ;) There is a lot of information here, much technical know how, and a pretty good bunch of folks that are happy to help.

 

That's an impressive pedigree! It's great to have you onboard, and I look forward to reading your posts.


Once you get to Novice status, please consider uploading some pics of your gear in the Members Systems area. We all like pics of all kinds of audio gear.


In the meantime, kick your shoes off, turn up the music, and welcome aboard.

 

giphy.gif

 

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Edited by johnrotten
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Welcome to the site @Elecdonia! I am impressed with your knowledge and skills of selling and servicing Carver gear! I too look forward to reading your posts about past experiences and current ones. What kind of gear do you have?

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Welcome Elecdonia!! Impressive background. Sure is good to have you. This is a great group of guys that are knowledgable and just a whole lot of fun. You will enjoy it. If you need it, ask for help. Everyone is very nice and willing to help out. Enjoy the great company here😁.

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Thanks everyone!

 

I'm blushing with all the attention my welcome post received. I'm sure that I will enjoy this forum! And I hope to be able to assist those who are engaged in keeping their Carver gear up and running and sounding great.

 

-Elecdonia

 

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