[Audio_Empire[_2_]]

On Thursday, December 20, 2012 1:16:46 PM UTC-8, Arny Krueger wrote:
"Scott" wrote in message

...



But none of these ABX DBTs that are being touted as scientific proof on

the subject...



Since nobody who really understands science and statistics is claiming that

ABX DBTs are scientific proof of anything, you would appear to be arguing

with yourself.



It is fundamental to science that all of its findings are provisional until

better findings are obtained. Therefore the very concept of some kind of

final "scientific proof" is itself nonsense.



In the one Stereo Review article about their big amplifier challenge one of

the amps was an old Futterman OTL. Strike 1



The amp in question was not an old Futterman OTL but rather it was a modern

amplfiier (in new product production at or near the time of the tests) that

happened to pattern itself somewhat after the origional Futterman OTL tubed

amp. There were many differences. If memory serves it contained solid state

devices, perhaps some in the signal path.

Tube amps are the exception. Many are designed to have the "tube sound" and
a DBT with a good solid-state amp will show definite differences that are by no
means subtle (in thet they stick out like a sore thumb. OTL amps are even more
so. Unless it uses a pair of transistors as the output stage, OTL have a relatively
high output impedance even if you parallel 8 pairs of output tubes! They just
can't be as neutral as a good S-S amp. The only time I've ever heard a OTL amp
sound great was when it was designed to be coupled to an electrostatic speaker.
Talk about a marriage made in heaven (or some-such place) the high output
impedance of the OTL and the high input impedance of the ESL, if designed to
be used together, eliminate two transformers.


If an underpowered antique OTL isn't being heard as different that should

tell you something about that set of tests.

Unless, as, I said above, the output stage is solid-state.

The amp in question was not an antique and was never operated beyond its

realm of linear operation so it was not underpowered. Strike 2

again it depends upon the OTL amp's output impedance. Futterman
did make several hybrid amps with tubed input and solid state
output. He called them Moscode amps. One was 150 Watts/channel and the
other was 300 Watts/Channel. They were called the Moscode 300 and the
Moscode 600 respectively. Was it one of those?



Your lack of technical understanding of OTL tubed amplifiers seems to

include a lack of appreciation for the fact that an OTL amplifier removes

any output transformer from the signal path, thus removing a large source of

inherent nonlinear distoriton and bandwidth limits.

....While introducing a fairly high output impedance unless you parallel a
dozen output tubes, and still you won't get the really low impedance
looking back from the speaker which is common with almost any
solid-state amp. Sometimes that's a good trade-off and sometimes it isn't.


If there was any kind of a tubed amplifier that would be most likely to

sound like an equally transformerless SS amplifier, it might be one

patterned on the old Futterman design. Strike 3.

No, I don't think so. Most OTL amps don't have the speaker dampening characteristics
that SS amps have. IIRC, the Futterman design was an exception and had an output
impedance of something like 0.5 Ohms (don't take that to the bank, I may be mis-
remembering here. It's been a long time since I've auditioned a pair of them. The
only thing that I thought the OTL didn't do as well as a SS amp (or tube amp with output
transformers) is bass. The Futterman OTL amp gave really "wooly" bass.