Thought on OTL tube amps

"...what we want to do is engage the human limbic system rather than the cerebral cortex "

That should be motto of every audio designer and it is ours, see - http://www.enjoythemusic.com/magazine/manufacture/0708/index.html

Yet, I cannot agree with Athmasphere that negative feedback is bad.

Our entire method of amplifier design is based on the approach which considers an amplifier as a control system. Because of this, our amplifiers are designed with an emphasis on very, very, very high speed control loops. The ultra-short transit time allows the amplifier to correct for many small errors; and the control loop can follow the input much more accurately. It does not (or very minimally) create odd order harmonics, it does not create pahse discrepencies and other garbage conventional NF does. These electrical characteristics result in a more detailed, transparent sound with less noise and louder yet cleaner musical reproduction.

Its very difficult to compete with OTL in harmonic richness for any solid state amplifier. I admit it. We are doing our best but its difficult. However, if don;t like heat, weight, tuning up, warming time and may be have difficult to drive speakers then - you are welcome to try our (and others) ss amps.....otherwise, everybody would own OTL amp...

Oh, almost forgot - there were a few well deserved praises to Jud Barber (of Joule-Electra) OTL designs but Jud does use very judiciously negative feedback....to control speakers even better.

I hope that after RMAF 2010, we will be able to add to this discussion of fidelity to true acoustic music we all strive to achieve and have in our systems.

Good Luck to Everybody.

At the risk of re-igniting the long-running debate about David Berning's designs, I would say in response to Spectron that the issues of heat and weight and difficult to drive speakers do not apply to David's amps, certainly not to the extent they do to other OTL's. I know someone with Joule 160's, and standing over them when they are fully warmed up is a good way to sweat off a few pounds in a hurry. In contrast, I can put my hand on the grill right above the power tubes in my Quad Z's and leave it there as long as I want, even when they are fully warmed up. And I have had preamps that weighed about as much as the Quad Z monoblocks.

Yes, let's not get into the issue of whether or not Bernings are or not OTL technically, they do seem to be in that camp to most users, and very fine sounding amps to boot.

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.