How Do The Carver Magnetic Field Amps Work?

D

DaveThreshol

More Q's than A's.....
I had a real Estate Sale haul today. I just picked up an M-0.5T at an Estate sale. It's 140/chan. @ 8 ohms, 220/ chan @ 4 ohms, Can somebody explain to my non Ohms Law brain, how those amps work? The Harmon HK870 I also got today is 100/ chan @ 8 and weighs twice as much. I thought they were like early digital amps or something. I guess he did away with the transformer?

Enlightenment needed. :)

Dave
 
Carver amps, And Sunfire for that matter, Go a different way than normal amps
in the power supply, and the transistors. He figured out some kind of down
converter, to lower voltage, That is he converts high voltage and low current,
low voltage and high current. I understand 90% of the input power goes
straight to the load(speakers), the power supplies are light 30lbs, for an amp
that can output 380wpc (Carver TFM-45). Carver does his circuitry differently,
but the 2 I've heard put out a huge amount of power(TFM-45/ZR1600), 380 and
400wpc respectfully.
 
Yep. The 870 is just a boat anchor. You better send it to me for proper disposal. :D

And welcome to AK!
 
The magnetic field amps do have a power transformer. What he did is put an SCR in series with the primary of the transformer, and he switches it on and off at a high frequency. He controls the power supply voltages by how long a time the SCR is on for, each time it turns on (he changes the width of the pulse to make it turn on longer.) Basically this is called a Pulse Width Modulated power supply. If you were to short out the SCR you would get a very high power supply voltage, like + and - 120V. It is adjusted for + and - 100V supplies. I haven't checked, but I think that the power supply circuit probably monitors the output and can put out a higher voltage for a short time, for transients.
 
Thanks everyone. Yes the tracking down converter, and I remember the PWM. The guy seemed to be a visionary. (?) But I think to really tell the new ideas from the blather, you have to know electronics to some extent, like this thread shows. I'll re-read the white paper.
 
Urizen said:
When you hear one, let us know. Thanks for the enlightenment.
Click to expand...

Exactly, I heard a TFM45 with 4312b's and it sounded very nice. I've read on
forums there popular to bi-amp and drive ribbon speakers, that soak up power,
(apogee/carver etc). There also known to have headroom to burn.
 
NeedForSpeed said:
Exactly, I heard a TFM45 with 4312b's and it sounded very nice. I've read on
forums there popular to bi-amp and drive ribbon speakers, that soak up power,
(apogee/carver etc). There also known to have headroom to burn.
Click to expand...


My first Carver was a TFM-35x. It handled sets of Advent and Bose 501, in parallel, with aplomb.

I use a Sunfire 300 with my Magnepan 1.5 Q/R in my main system. It never runs out of steam.

I believe that Bob designed these types of amps around ribbons and planars.:yes:
 
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Urizen said:
My first Carver was a TFM-35x. It handled sets of Advent and Bose 501, in parallel, with aplomb.

I use a Sunfire 300 with my Magnepan 1.5 Q/R in my main system. It never runs out of steam.

I believe that Bob designed these types of amps around ribbons and planars.:yes:
Click to expand...

I would agree, With the kind of output these put out, For home audio no
less, We haven't touched the guys Pro Amps..Xi2600, 510wpcx2 at 8ohms.
Weight, 28lbs. The guy is a crazy nut for wattage!:screwy:
 
Sansui Louie said:
From the couple of them that I've seen, they work best as a doorstop. Though they're kind of light for that, too.
Click to expand...

Ouch! :nono:

I can see where they may not be every ones "cup of tea", as far as sound goes, but you have to give Bob some credit, he has produced some very fine and innovative gear over the years, and although I have no experience with it, his Sunfire line up has had some very good write ups.

I have owned a few items from Bob Carver in the past, and I currently am running a CT-23, TFM-55, and a AV-405, that I couldn't be happier with. The TFM-55 has way more output than I could ever need for the Klipsch Chorus speakers I have it hooked up to. Of course, at 101 Db efficiency, the Chorus's would make a good amount of noise with 10 watts, never mind 380 per channel!

I like Loud, Loud and me have been best friends since before puberty, yet I don't think I've peaked the TFM-55 at more than 50-60 watts since putting together this latest combo (TFM-55, CT-23, Chorus I's). I'm happy, Loud is happy, and I bet Bob Carver would be happy as well, knowing that Loud and I are having a great time listening to our favorite tunes through his gear!

You're OK in my book, Bob! :thmbsp:
 
Magnetic doorstop and Magnetic field power amplifiers
To each his/her own, is in the eye of the beholder.
(thanks for the pic Avrisers)
 
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I have now repaired about 8 of these amps, all with minor problems; bias mis-adjusted, bad solder joints, dirty pots. I have only seen one that was DOA and that was because some so - called tech finger @##%%^-ed it. He had it mis-wired and also left out a screw that provides a common ground for the amp. Anyway, I find that they sound very good. These amps I worked on looked like they have had rough use, and they stood up to it, they seem well built to me.
 
My memory of this is hazy, but IIRC when Stereo review tested the original Carver Cube (M-400 or something like that), it ignited and self-immolated. I think even Julian Hirsh may have commented on the uniqueness of that (although he was loath to ever say anything critical, or distinguishing, about any amplifier).

Y'all do know, don't you, that, in some circles, he is known as "Sideshow Bob" Carver?
 
I've used several Carver "M" models at home and "PM" models for sound reinforcement.

Had one PM1400 that was initial defective with a bad circuit board trace, and the larger models, say M1.5/PM1.5 and up are definitely AC line sensitive needing good stable "fat" AC mains power to perform to their limits.

They're very good sounding amplifiers that i've spent many hours using and abusing................... I cannot think of one legitimate complaint in my experience outside of the above mentioned.

Other's mileage will surely vary.................
 
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