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 audiokinesis

I own and sell both OTLs and SETs, and would say that they have many of the same qualities. At the risk of overgeneralizing, I'd say that OTLs tend to be a bit more lively and dynamic and SETs tend to be a bit sweeter and warmer (I can comment some on why if you'd like). I've heard superb presentations from systems with both types of amplifiers.

Since it sounds like you have a single Atma-Sphere amp, I presume it's an S-30. As long as you don't ask it to drive a speaker whose minimim impedance dips below 7 ohms you should be fine. An SET would be much more forgiving of lower speaker impedance, as would the larger Atma-Sphere amps. On the other hand if you pair the S-30 with a 12 or 16 ohm speaker, it sounds even better and will put out more power (roughly 45 watts into a 16 ohm load).

The S-30 is definitely a specialty amplifier when it comes to loudspeaker matching. Are you looking for speakers, and if so what are your requirements and ballpark budget?

Duke
Hi Otto,

If I understand correctly, you're driving the Thiel 3.6's with your S-30. The Thiel's impedance is way below what the S-30 is comfortable with. Apparently you tried the Silverline Sonata also but it didn't have enough bass to do justice to Mahler ("Mauler"?).

High efficiency, ultradeep bass is the most expensive commodity in audio, both in money and in real estate (due to box size requirements). I'm sure you've thought of this, but one possibility might be easier-to-drive but bass-limited main speakers plus a subwoofer or two.

Another possibility is for you to keep the Thiels and use an autoformer to make life easier on your Atma-Spheres. Pauls Speltz's "Zero Autoformer" has saved the day for many an Atma-Sphere owner, and I have customers who use it with more conventional transformer-coupled tube amps. In the majority of cases the Zero is a significant net improvement, but not always, so it's best to try before buying if possible. I do think it would be in your case. I just sold my demo pair or else I'd offer to let you try them.

Pardon me now Otto, but since I've mentioned and suggested something I sell, there's a matter that I have to take care of. I have a stalker who sends me threatening e-mails when he perceives my posts as being overly commercial - according to his criteria, rather than Audiogon's. This morning I got one from him because of my first post in this thread, and I'm sure my mentioning the Zeros will cross the line he has drawn.

Stanhifi, I am tired of your threatening e-mails. Please stop sending them. Don't e-mail Otto as you threatened to either. If you have a problem with my conduct on Audiogon, let's get it out in the open. Go public and take your best shot, or leave me alone.

And Otto, if Stan does e-mail you to attack me, I would very much appreciate your letting me know. I'm not trying to hijack your thread so I invite you to let me know via e-mail if you'd rather, but I'll leave that up to you.

Okay getting back to Otto's situation, note that if you do go for a high efficiency, easy-to-drive fullrange speaker that has genuine deep bass you're talking about a very big enclosure. Without an idea of your price ballpark I hesitate to make specific recommendations among new speakers. In used speakers I'd suggest the big Altec Model 19's which show up occasionally for ballpark a grand or so used (more for a pair in very good condition, but still less than new speakers of comparable performance).

Finally, is building your own enclosures a possibility? If so, prhaps I can offer a suggestion or two that would work well with the S-30.

Duke