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RE: From what I understand the Zero's...

Chris, You and a few others are the ones taking the purist stance. I have no desire to argue the point except to say what I said. Yes, the Zero is a kind of crutch to improve the match between an OTL and a typical low impedance speaker. That doesn't bother me. Most people who have employed zeros with their Atma and other OTL amplifiers report that they are happy with the pairing. I was too, until I found a way to modify my speakers to raise both their efficiency and impedance curve such that I no longer needed to use the Zeros. As you know, too, there are also ways to reduce the output Z of many OTLs, by adding NFB, that also might do the job and obviate the need for Zeros. It depends upon which is the lesser of two evils. It's all good, so far as I am concerned.

I would maintain though that a well designed autoformer, like the Zero, used at a 2:1 impedance ratio (I never went above 2:1; the Zeros permit up to 4:1, I think) is in fact likely to give wider bandwidth and lower distortions compared to a true audio output transformer as found on most OTC amplifiers, driving the same speaker, for reasons noted. If you want to say that an autoformer-coupled OTL no longer fits the strict definition of an OTL, I would not argue with that.

One other small point, the Zero is placed at the speaker end of the path from the amplifier outputs, not at the amplifier end, for whatever difference that makes. You might say it acts on the speaker. But I don't want to go there, either.

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