Axiom Home Page Forums General Discussion Stereo Upgraded Vintage Amp Makes M60's Soar!

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--

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?

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?

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.

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

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--

Cool!

Every time I see "Bob Carver" my mind keeps reading John Carter. Especially when mentioned along with terms like "magnetic-field coil."

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

thanks everyone for all the info.

that sounds a lot like today's class G amplifiers

Yes it sounds like it, but not really, since there is no digital circuitry involved.

I always liked Carver amps. The first thing I think of when I see Carver is, Carvers Amazing Loudspeaker.

Copy.....and pasted:

Me, I remember the cube amp. I always liked the idea of Carver.

Bob Carver, it seemed, had that ability to look at a problem and find a path to a solution that no one else had traveled.

Might we be looking at the same thing here with the new M100?

I just read the thread on the "as yet unnamed" omnidirectional speaker / DSP creation and yes, it sure sounds like it! Very cool!

Next, I think Axiom should look into bringing this efficient amplifier technology back! Sure would fit in with the current times IMHO where less bulk and higher efficiencies rule...hmmmm...the new speaker requires extra amp channels... whaddaya think Axiom brain trust??? The only odd component is the "magnetic field coil". Since the "BobFather" is on to ultra hi-end tube stuff, maybe he'd give up the patent cheap?!?!

I have one of those little Carver cube amps. 201 watts per channel in to 8 ohms. Still works fine but I should probably send it in to be redone.

MarkyM, any suggestions as to where I might be able to get this reworked?

I also have a Carver cd player from the late 80's that works just fine.

Ed, just send that amp down my way. I'll see how well it works

You got it Rick, but then, when the caps and capacitors need fixin', you gotta send it in and fix it up for me!

I tell ya, it sure does a hell of a job making the M80's pound when I get the notion to hook them up to it.

Plus, it is fun to watch the LED lights bounce up and down when it is cranked up.

I miss meters....VU, LCD, Fluorescent...whatever.

I hear ya Mark. I have an older HH Scott receiver with vector tuning and power meters. I still use that one as well with one of my pairs of M3's. Takes me back to my college days!

I'd love to get a big ass vintage amp with some VU meters.

Until then, you'll just have to watch your avatar!

LOL!!

Yes, you can try Bob Carver's Audio Service (formerly Rita's Vintage Audio): http://www.ritasvintageaudio.com/

Awesome, thank you very much Marky!

Merchman, H.H. Scott amplifiers, tuners and receivers were wonderful.

Mapleshade upgrades the Scotts. When I have room for another 2 channel system, I hope to get one of those.

By the way, this one's for you ...

Is that think beautiful or what?

You want analog meters do you?

Carver has an amp for that too! (and this is the only other one besides the 1.0t that they do the Mk2 mods to):

Nice!!

Yep, that is a nice looking amp, Marky! Always wanted one of them.

There ya go Wid, buy two and send me one!

Do want!

Me wanty too! Nice.

hmmm...and I thought people in Axiom forum mostly do not believe in more power = better equation?

I did mentioned that when I 1st got my XPA-3 and you guys said I am wasting my money and my mind is playing with me for what I heard of better sound came out from my M60.....

mpyw, I think you'll find people on both sides of equation here, as you will on any other audio forum. A lot of it has to do with how much room you are filling with sound, and of course, your desired listening level but at lower levels or smaller rooms extra power is just unused power.

If the first watt is no good, who cares how many more like it are lined up behind it.

SET Tube amplifier (5-10 wpc) + M3 speakers + sub = audio bliss

Michael, "believe" has nothing to do with it. Audio equipment is technology, not theology, and measurements of amplifier power required are a matter of applying well-established principles with a little relatively simple mathematics. This isn't a matter of personal opinions and isn't decided by vote.

Most of time the listening you described in your previous thread would have used only a watt or two and none of the reported observations reflected the reality of the situation. Your sincerity isn't in doubt, but you simply can't apply the simplistic "Just trust your ears" standard in judging amplification. Blind listening tests at carefully matched voltage output levels(which you didn't do)fail to support mythologies surrounding magic amplifiers.

Well, that put a damper on things

I had a SET and I sold it before I got my M3s. I really wish I still had it and I might replace it some day. It was beautiful, and used they are not too expensive. I can have my big tube amp modded by the manufacturer with an option to use the pentode tubes as triodes(with less power output). I am thinking of doing it because I have it mated with the 3s for late night bed room listening. And it will be fun.

I am also thinking about adding a little sub to the bedroom mix.