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#369633 - 03/14/12 09:20 AM Upgraded Vintage Amp Makes M60's Soar!
MarkyM Offline
enthusiast

Registered: 11/13/10
Posts: 37
Loc: Ohio
Up until recently have been using the built-in amps in my Denon AVR-3808CI for stereo music listening. I needed to use the AVR's "Stereo" mode in order to use the DSP-based built-in 80Hz crossover to my equalized SVS sub. Direct mode, sending the full-range signal to my M60v3's, does not work in my room due to a big room peak between 35-55Hz. Also, at least in my room, the M60's have absolutely no need for any of the DSP-based features of the AVR, including the Audyssey "calibration" which did nothing to tame my low bass room peak.

I had been looking at Emotiva etc. but most good new amps these days are kind of large, heavy and pricey. So I decided to take a chance and picked up a vintage Carver M1.0t magnetic-field amp (circa 1987) to drive the M60's. Now the AVR can run in the much better sounding "Direct" stereo mode which is pure analog except for A to D and D to A conversion where required. I dug out my old Outlaw ICBM analog crossover (from the analog-only SACD/DVD Audio days circa 2001) to maintain the proper 80Hz crossover.

In a word...WOW!

I had never been a believer that the power amplifier could make such a huge difference. I am now!

The M60's have always had great imaging but now they sound like the ultimate poor-man's line source ribbon speaker! Also, IMHO the M1.0t's original "tube-like" transfer function is a match made in heaven for the Axiom tweeter.

The stereo image is wider and smoother, the sound is more "liquid", effortless and musical.

The stock M1.0t is rated at 200w/ch. Is all that power really needed for the M60's? Certainly not, but this is not about power ratings. (plus it's kind of nice to have more than 20dB of headroom above 90dB for the occasional recording that still has actual peaks!)

Since the amp is nearly 25 years old, I sent it to one of the members of thecarversite.com to have it re-capped (all electrolytic capacitors replaced - these generally have a life of no more than about 20 years) - and modded to what they call the "Mk2". The mod stabilizes the bias circuit for cleaner operation at all temps as well as reducing distortion at all levels including lower levels. A side-benefit is even more power - it is now rated at 400w/ch! at 8 ohms.

This thing should be all set now for another 25 years. It barely gets lukewarm after driving the M60's at reasonably loud levels for a few hours.

Bob Carver is now into handmade tube amps and ribbon speakers in the $20k+ range but there are plenty of these beasts on the fleabay for about $300. The re-capping and mod is about another $300 so for $600 you've got IMHO one of the best amps ever designed and a perfect match to the larger Axiom speakers. (not sure how it would be into the 4 Ohm M80 though)



--Mark--






Edited by MarkyM (03/14/12 09:28 AM)
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#369641 - 03/14/12 10:21 AM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
dakkon Offline
connoisseur

Registered: 02/08/04
Posts: 1863
Originally Posted By: MarkyM
So I decided to take a chance and picked up a vintage Carver M1.0t magnetic-field amp (circa 1987) to drive the M60's. Now the AVR can run in the much better sounding "Direct" stereo mode which is pure analog except for A to D and D to A conversion where required. I dug out my old Outlaw ICBM analog crossover (from the analog-only SACD/DVD Audio days circa 2001) to maintain the proper 80Hz crossover.



I like how something in the 80's is now "vintage" and 2001 is now a long past memory of the "prehistoric period of analog"... hehehe...

I have always been a firm believer in power amps... The amps i have are 250W @8ohm, and 500W@4 ohms... Power isn't was kills speakers, it's distortion.. with a quality amp, you can drive speakers well beyond what you would be able to do with a receiver...

How much does your new amp weigh compared to your Denon? That is for only 2 channels of amplification, not 5-7 as well as all of the other ancillary circuitry in the box for video and audio processing!


BTW, my amps are circa 1997.... I am going to guess the carver is a class A amp also?

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#369655 - 03/14/12 11:05 AM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
J. B. Offline
connoisseur

Registered: 01/19/11
Posts: 1291
Loc: Quebec, Canada
i'm very curious to know what class amp this is.
i don't think it's a class A amp because at a rating of 200-400 WPC, the amp would need to be very large in order to accommodate huge heat sinks or a powerful fan in order to get rid of all that heat.

i also don't understand how the amp power output jumped from 200 WPC to 400 WPC; i guess the transformer would have had to be changed for that; and then, would the circuitry accept that much more voltage without breaking down?
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#369668 - 03/14/12 12:04 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
Brent Offline

buff

Registered: 03/13/01
Posts: 59
I sold an awful lot of Carver amplifiers - good amplifiers - BoB Carver used many different names for his amplification, magnetic field etc. good hype - however in reality they are a class A/B amplifier.
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#369669 - 03/14/12 12:08 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: J. B.]
alan Offline

connoisseur

Registered: 01/29/02
Posts: 3261
Loc: Toronto/New York/parry Sound
Hi J.B.

All of Bob Carver's amplifiers were Class A/B designs, including the M-1.0t. If memory serves, he never built or marketed a pure Class A design.

It was listed in the 1988 Sound&Vision (Canada) Audio/Video equipment directory (which I edited) as having a power output of 200 watts/channel into 8 ohms and 400 watts/channel into 4 ohms.

Regards,
Alan
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#369671 - 03/14/12 12:16 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: J. B.]
MarkyM Offline
enthusiast

Registered: 11/13/10
Posts: 37
Loc: Ohio
Correct J.B, it is not Class A.

dakkon, it only weighs 24 lbs.

Actually, as I understand it, the amplifier circuitry itself is conventional class AB. It is the power supply that is VERY different.

With conventional amplifier power supplies, the power transformer and rail caps need to be large enough to keep the rail caps charged all the time, so that the full DC power is always "ready" for any large signals that might come along. Bob Carver, in IMHO quite a stroke of genius, came up with a much more efficient way to supply high DC power only on-demand.

So the power transformer in these amps is very different and is called a "magnetic-field coil". This, along with a triac, allows the amplifier to consume very high power only on-demand but run much cooler and more efficiently. This also allows it to have much less bulk. There are multiple voltage rails that are switched between as needed. The M1.0t has 3: 32v, 67v and 112v. Most of the time it is "loafing" on the 32v rail.

That is a way over-simplified explanation. If anyone would like to see the full details, all of the historical material is available here:

http://www.thecarversite.com/yetanotherforum/

Select "Carver / Sunfire Amplifier Technology" and there are a number of fascinating documents available there including "The Carver magnetic field amplifier story, parts I, II and III"

--Mark--


Edited by MarkyM (03/14/12 12:23 PM)
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#369689 - 03/14/12 12:49 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
tomtuttle Offline
axiomite

Registered: 06/20/03
Posts: 8488
Loc: Tacoma
Cool!
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#369691 - 03/14/12 12:55 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
Murph Offline
axiomite

Registered: 10/05/06
Posts: 6955
Loc: PEI, Canada
Every time I see "Bob Carver" my mind keeps reading John Carter. Especially when mentioned along with terms like "magnetic-field coil."
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#369696 - 03/14/12 01:07 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
dakkon Offline
connoisseur

Registered: 02/08/04
Posts: 1863
Ah, my 2 channel amp weighs 43lbs. and has a normal operating temperature of 97 degrees F.. And consumes 250W while idoling!... The owners manual does not say how many voltage rales it has.. but says the normal RMS voltage is 49v...

The A/B design is a much more efficient design.. so you can get much more power out of a smaller package, with less energy "waisted", but if you want a nice space heater. Class A all the way laugh

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#369705 - 03/14/12 02:03 PM Re: Upgraded Vintage Amp Makes M60's Soar! [Re: MarkyM]
J. B. Offline
connoisseur

Registered: 01/19/11
Posts: 1291
Loc: Quebec, Canada
Originally Posted By: MarkyM
Correct J.B, it is not Class A.

dakkon, it only weighs 24 lbs.

Actually, as I understand it, the amplifier circuitry itself is conventional class AB. It is the power supply that is VERY different.

With conventional amplifier power supplies, the power transformer and rail caps need to be large enough to keep the rail caps charged all the time, so that the full DC power is always "ready" for any large signals that might come along. Bob Carver, in IMHO quite a stroke of genius, came up with a much more efficient way to supply high DC power only on-demand.

So the power transformer in these amps is very different and is called a "magnetic-field coil". This, along with a triac, allows the amplifier to consume very high power only on-demand but run much cooler and more efficiently. This also allows it to have much less bulk. There are multiple voltage rails that are switched between as needed. The M1.0t has 3: 32v, 67v and 112v. Most of the time it is "loafing" on the 32v rail.

That is a way over-simplified explanation. If anyone would like to see the full details, all of the historical material is available here:

http://www.thecarversite.com/yetanotherforum/

Select "Carver / Sunfire Amplifier Technology" and there are a number of fascinating documents available there including "The Carver magnetic field amplifier story, parts I, II and III"

--Mark--



thanks everyone for all the info.

that sounds a lot like today's class G amplifiers
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