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Thought on OTL tube amps

Just curious....how do these sound/perform compared to tube amps with transformers? Why do you prefer one or the other? Any particular brands of OTL amps you would recommend listening to? You can see my system on my tag here...listen mostly to rock and roll with a smattering of jazz and a bit of classical once in a while. The next stop on my amplifier adventure is an OTL model, and I have no intention of trading it for either SET I currently have, as I'm very happy with both. One of the ways I enjoy experimenting with different "sound" is by switching up the amps. Just trying to solicit some opinions, of which I know there are many strong ones here at A-Gon. Thanks in advance!
afc
ghostrider45
449 posts
 
Most SS amps are OTL. Transistors are intrinsically low impedance devices and most circuit topologies don't need an output transformer. Tubes are high impedance devices and most circuit topologies do require a transformer to drive low impedance speaker loads.
glide3
402 posts
 
I really enjoy OTL amps and have owned examples from Tenor (75w, 75Wi), Atma-Sphere (M60, MA1) and, Joule(VZN 100) and Berning (Siegfried, 270 and ZH 230...this one I use currently).

I have not had reliability issues with any of these or certainly any more than any other tube based amps.

They require careful speaker/system matching...your speakers would likely work well.

There is a transparency and immediacy to the sound that is very appealing to the OTLs they can also do bass and highs very well if set-up and used properly.

I would say that overall they are my favorite type of amp...but like you, I have several (types of amp) and enjoy the virtues of all.
I have yet to find anything that is perfect in all cases.
stanwal's avatar
stanwal
3,147 posts
 
Macintosh is the only SS amp using output transformers that I am familar with.
mcfarland
356 posts
 
The Atma-Sphere web site (Atma-Sphere.com) has several "white papers" explaining many of your questions. I own a pair of M60Mk2.2's. Absolutely stable, (you can even short the outputs, and switch output tubes while running, though I would not recommend doing so (I have seen Ralph Karsten do it) and I have had no problems. Happy Listening.
simontju
257 posts
 
"Blow a tube with your OTL and you could fry your speakers. Great sound, but some risk if you listen loud, or run tubes till they drop "

Properly designed OTL amp represent no more danger to speakers then properly designed regular tube or transistor amps.

For example, in many tube amp designs, output tube is connected to resistor which work as a "fuse of last resort". if output tube blows then it takes out this resistor.

I never heard that OTL amps by Joule-Electra and Athmasphere produce any troubles. I suspect that with proper maintaince these amps can work half century or longer - at least I see not a single reason why not?
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