Pass Labs XA30.5 and ModWright KWA150

So designer of OTL amp believes that output transformer is BAD (for his varous reasons) and did everything he could to create...OTL (OutputTransferLess) amp and you saying basically to him - you did huge job to eliminate output transformer but I will install it into the signal path ANYWAY and destroy your intention and your goal...and your sound.

Michael_moskowich (Threads | Answers)

I have owned Atma-Sphere amps on and off, and I have had some extensive email discussions with Ralph. For exactly the reason Michael_moskowich highlighted, the issue of using ZeroFormers with OTL amplifiers has always struck me as being counterproductive to the goal.

I agree, though I have never heard the ZeroFormers with the M60s (don't need them), there is something about the very idea of it that doesn't quite feel right - even if they work.

What is the purpose of owning an OTL amp if you're adding an autoformer?

Because it might still sound great with an autoformer. For instance, it is still a Class A, triode amp. But I do agree with the general idea (not based on any technical knowledge at all)that there is some dissonance in the idea of using an autoformer when you have purposely decided on an OTL amp.

I agree with all of the statements about using an Autoformer (I don't use one and this is one of the reasons I went from M-60's to MA-1's) with Atma-Sphere amps.

When I ran tests with and without the Speltz Autoformer, I could always pick out when the Speltz Autoformer was being used. Anybody who tells you that it doesn't have a sonic signature is definitely fooling themselves - it is there.

However, Atma-Sphere amps + the Speltz Autoformer still sound better to my ear than most amps I have tried. The sonic penalty you pay for inserting the Speltz Autoformer isn't huge and is far less significant than the sonic improvement one gets by raising the impedance that the amp sees via the Speltz Autoformer.

George