OTL or SET? Differences?


With my limited knowledge, I know that OTL is transformerless and SET is single-ended. But what are the main advantages and disadvantages of these two designs? How to choose matching speakers for these two different designs?

Currently I have an Atma-Sphere OTL amplifier.

Thanks in advance!

Otto
yu11375

Showing 2 responses by rushton

Yu11375,

The Atma-Sphere MA-1 and MA-2 amps are far more flexible in handling a wide variety of speaker loads than the lower output Atma-Sphere amps (S-30 and M-60). With the increased number of output tubes, they have much lower output impedance (as well as higher power) making them much more flexible partners. The MA-2 will drive just about any speaker whose minimum impedance doesn't drop materially below 3.5 ohms. With the MA-1, you need to be a bit more careful in speaker matching, but still a broad selection. With either the MA-2 or MA-1 and appropriately matched full-range speakers, you will get bass impact, resolution and agility that is as good or better than you can get from the best solid state amps I've listened to. Plus, you get that magical reproduction of timbre and harmonic overtone structure that only tubes provide.

In contrast, SETs, as mentioned above, deliver a magical quality through the midrange that can be quite addictive. SETs are often described as sweeter and more "musical;" never quite "accurate," but making the music more beautiful than real -- all of which can be a good thing given all the trade-offs we work with. But, a big trade-off for a classical music listener is that I've yet to hear any SET/speaker combination that can begin to deliver on complex orchestral music (like the Mahler 2nd) or large organ. (There may be a combination of SET and horns out there that does this, I just haven't yet heard it.) If your primary listening preference is small ensemble jazz or chamber music or singer songwriter, SET can be a wonderful way to travel. But be prepared to trade-off on more complex music and on music with substantial mid- and low-bass information.

On the flip side, the Atma-Sphere OTLs will be very neutral, very detailed, highly resolving -- in the words of a listening partner here: pristing like a clear glass onto the music. They won't make the music more beautiful, you'll simply get what's coming from your front-end source without editorial.

N.B., I'm an Atma-Sphere MA-2 and Avalon Eidolon owner.
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Tubegroover, thanks.

Audiokinesis/Duke, you're consistently one of the most balanced and helpful people posting on Audiogon. I'm amazed someone has made a point of attacking you; that's unconscionable. Thanks for all that you've added here over the years, and I hope the nonsense doesn't put you off.

Ralph, I've never heard that hysterisis loss explanaton before. Thank you.