OTL amplifiers

Tubegroover, Harvey DID have his inspired moments, which this "child" must have sprung out of. I alas, was not that lucky. By the way, I would imagine that this combination, you've mentioned, must sound absolutely heavenly.....

Thank you Detlof, I have no plans or desire to replace ANY of my "sources".

Hi!
(Some)OTL amps are amongh the best sounding amps on the planet. They mostly are very expensive but their performance justifies the investment. As Wellfed pointed ZERO Autoformers are the solution (except for the heat dissipance). And not only for OTL designs! You should check the Paul Speltz Website and read/learn about them. After a month (or so) of extensive use i became a believer. They are my next "investment"!
Cheers!

I really cannot add much to the advantage/disadvantage of OTL amps, except to say that they certainly do possess a magic and realness that is hard to beat.

But, I would like to say something about the Zero autoformers. If they work for you, and you like them, then please just use them and be happy. However, I feel they are not a good solution whatsoever. They steal most of the OTL magic out of the sound, imparting a very white, bleached sound which makes me feel as if I am listening to solid state.

In my experience, the way to do it is to find speakers which present the amp an OTL friendly(that means high impedance) load.

Not to take anything away from Paul Speltz; the man is obviously a genius, when it comes to AtmaSphere amps, and his mods boggle the mind. Using the Zero autoformers will allow people with not the best matching speakers to be able to use OTL amplification. But again, it simply does not sound nearly as good as doing it the right way.

I agree with Trelja that finding an OTL friendly speaker is the optimal way to go, but I did have exceptional results with the ZEROs and a previous set of speakers that, on paper anyway, were a good match for OTL amps (nominal 8 ohms that never dip below 6.5 ohms). I obtained these results by using an alternative 2X configuration that I understand involves using less of the windings in the autoformer. Using this configuration, I was able to retain the refinement of the Atma-Sphere M-60s, in the process though bass performance suffered. I then put a second pair of ZEROs, using standard 2X configuration, on the woofer binding posts and the overall performance of the system went through the roof. The whole spectrum was improved, bass performance was phenomenal, and the mids and highs benefited in major way as well. The resolution of the system improved enormously. I had strong expectations that by using the second pair of ZEROs I would get the bass performance back that was lost when switching to the alternative 2X setting. I ended up with performance that vastly exceeded the sum of the parts - making me a wildly enthusiastic believer in the ZEROs. I now use a pair of speakers that are rated at a 10 ohm nominal impedance and I achieve better results without the ZEROs.