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In Reply to: RE: ADH isn't a class, like class A or D, its a marketing thing with a trademark posted by Freo-1 on March 31, 2022 at 09:25:16
There are two amps: a high power but lower accuracy amp and a low power but very hi accuracy amp. The low power amp is driven with a correction signal and it's output is added to the output of the high power amp such that the combined output is as precise as that of the low power amp alone. Or something like that. I've heard it described as a form of feed-forward.
Edits: 03/31/22Follow Ups:
Peter Walker must have been born on another planet. I have Quad 57's and a current dumping amp for the quads as well as a few different amps.I remember something like the low power amp is class A driving 2 class C amps, one + the other - , and the waveform put together to then drive the speaker. That's a lousy explanation and I forget how it's done exactly but it sounds quite good. If I also remember correctly, he also invented tertiary windings on output transformers that was later used by McIntosh but received no credit for that.
I once mailed Quad across the pond for help restoring my Uncle's 1957 57's and he personally mailed me guidance and original picture manual of the Quads and how to update them. Back then at 21 Y.O. I didn't recognize the significance of that, what can I say.
edit - I was wrong, it's 2 class B sections not class C
Edits: 04/03/22
Best sound I ever got out of my partially refurbed 57s was with a passive attenuator driving a pair of completely refurbed Quad II tube amps. Never seriously tried them with anything solid state.
NT
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
over the last 40 years of playing music thru them with different amps, they can be extremely revealing. Back then I tried a Phase Linear 400 through them and that was bad. The usual import receiver with loads of feedback was bad. I don't know anybody local with Quad tube amps, my Uncle had a Dynaco Stereo 70 and I have a few different including Mark III's.
Quads have euphonic qualities, at least the 57's. They also throw a wide spacious soundstage beyond the left and right and have a good sense of depth. You can't tell where the mid/tweeter panel is, even with my plain speaker cloth and metal screen long gone. Revealing of sources, yes, so much so that deficiencies in recordings are plainly evident. My quest is over except for music where the money should go.
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