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Re: I do use OTL's and personally love them...

Posted by Lew (A) on October 20, 2004 at 12:39:16

In Reply to: Re: I do use OTL's and personally love them... posted by Rich Brkich on October 19, 2004 at 14:05:14:

Rich, I mean this only in the gentlest way, but since your own last name appears to be shy a few vowels that is perhaps why you did such a bad job of spelling the names of the most well known OTL designers. You got Julius' name correct, but after that it's "Rosenberg", "Karsten", "Judd (Barber)", and "Rozenblitt", respectively.

I can provide some history dating from Futterman forward. I had the privilege of knowing him, and in the 70's he built two sets of monoblock amplifiers for me. Whatever one may say about the sound of those amps, they were dead nuts reliable in my hands. I kept the second pair of amps for about 20 years and changed the output tubes once after 10 years, only on the empirical judgment that 10-year-old tubes probably needed to be replaced. Bias-ing them was a 10-minute job using Julius' instructions and a voltmeter. Also, let me say that he was one of a breed of craftsman that is in all too short supply these days. He was honest and caring, and he really sold his time and products too cheaply. In the late 70s, Harvey acquired the rights to build amps with the Futterman type OTL circuit at NYAL. I never heard or owned a pair of NYAL amps, so I cannot comment on their sound or reliability. George Kaye, an engineer who worked for NYAL, made some mods to the Futterman circuit to improve the bass performance. In the 80's there were several other iterations of the Futterman-type circuit (single-ended, "totem pole" output circuit). These included the Counterpoint SA4, the KSS amps, the Fourier amps, Prodigy monoblocks, and eventually Transcendent. The Counterpoint and KSS products were apparently very unreliable, and it may have had something to do with the fact that both designs did away with the output coupling caps that were in the Futterman circuit to protect the speakers from DC. Fourier amps were also unreliable but perhaps for different reasons, maybe due to quality of construction issues which also apparently plagued the KSS. I owned a pair of Prodigy amps in the early 90s, and they were also totally reliable and were built like tanks, sounded better than my earlier Futtermans. Rozenblitt made some changes in the basic Futterman topology that apparently also improve bass performance and overall sound quality for Transcendent compared to all the earlier products. And of course the Atma-sphere amps are a totally different animal, using a balanced input circuit and a balanced output based on the circlotron, no relation whatever to Futterman's original design. My Atmas are indestructible and it is almost impossible to imagine how they could ever damage a speaker without gross abuse. In summary, the whole notion that OTLs are inherently unreliable is baloney and always was baloney, probably perpetuated by makers of other types of amps that cannot compete with OTLs in sound quality.

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