Thought on OTL tube amps

The atmasphere amp is a great match for Soundlabs. Soundlabs generally are very full in the midrange and atmasphere goes very well with them.

negative feedback....to control speakers even better.

Negative feedback cannot be used to control speakers. It can only be used to control amplifiers. The idea that it helps with speaker control is part of the myth of damping factor, a subject that has its own thread on this forum right now.

This myth has heavy subscription by the Voltage Paradigm camp- see the link I provided in my second post to this thread. It is true that higher speeds in the amplifier will reduce odd-ordered harmonic generation when feedback is applied, and it is also true that the amount of this is variable from amplifier to amplifier, and does account for some of the differences that we hear.

Most OTL manufacturers use feedback. I think that we are one of the very few that do not. It is true that this limits the speakers that work with our amps, but it is not a matter of speaker control- usually its a matter of tonal issues related to incorrect voltage response for that speaker. Our philosophy is that if the speaker requires feedback for the amp to work with the speaker, there will be no way that speaker will ever sound like real music as the amplification will be inherently incapable of the task. It might sound like a good hifi, but that is not our goal.

There is no question that this philosophy has been a major marketing problem for the company, and it has contributed to the idea that OTLs are load sensitive (again, see the link I provided earlier). But if you want it to sound real that's what you have to do as its all about human perceptual rules. In the end, this means that there are dozens of speakers that work with our amps rather than hundreds.

Hi Athmaspere.

"Negative feedback cannot be used to control speakers. It can only be used to control amplifiers. The idea that it helps with speaker control is part of the myth of damping factor, a subject that has its own thread on this forum right now. "

Dumping factor is a "myth", I agree with you 100%.

I also agree with you that more accurate describtion of Jud Barber use of negative feedback in his OTL amps leads to control amplifier for....for......for...better sound coming from ... from...speakers. So lets not play with words ( it is not presentation of peer-review technical paper here)

If you do not use negative feedback then its great for you, however, in my eyes its not the virtue either. I will propose that for every technology used in amplifier design there is its own advantages and its own disadvantages. Otherwise we all would use one "perfect" design. Solid state amps have class A, AB,C, D etc. Tube amplifiers have traditional push-pull, OTL, SET etc.

I firmly believe that its not "what" technology you use is important but "how" you use it and sonic results are that count at the end. Obviously, each technology has some advantages specific to it e.g. low weight per watt of power in class D - but by itself its totally useless

Finally, regarding gorgeous OTL amplifiers (and I am lover of them!!!!) I can only repeat you conclusion:

" In the end, this means that there are dozens of speakers that work with our (OTL) amps rather than hundreds." - Sure and when it works its spectacular !!!

In our approach (i.e. control theory, which I believe unique in this industry), we are trying to match not only hundreds but every speakers available to produce musically involving sound comparable to the sound of acustic music.

Sounds like the Spectron approach would lead to broadbase good and the Atma-sphere to a narrower range of as good as it gets - certainly a market for both approaches. With my speakers its the OTLs I would go with, with Thiels or B&W, perhaps the Spectron approach would make more sense.

Hello Jwm,

I just wanted to let you know you're not alone in your thoughts. At least with regards to the brand I heard driving my speaker. Although it does have some wonderful audiophile traits overall the faults I hear ruin the illusion for me.

best,
Tom