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What's your OTL tube amp experience and suggestion?

Are OTL amps in general much less reliable due to their nature, or due to the implementation quality, or both?

Perhaps this has been discussed a zillion times in the past.   Perhaps, however, makers have now improve on past experience?  So it could be worth re-visiting.

My past encounters with OTL tube amps are among the most negative: Wonderful (but never great) sound during the brief period that they work.  Otherwise, major fire hazard.  Overheating, red hot plates, sparks, consistently toasted fuses, burning smell, you name it.  My past OTL amps are like crying babies on an changing table - don't you ever walk away from an arm's distance.   The used market seem to reflect such as well --- way more 'as-is for parts' or 'totally refurbished' units than reliable 'used' units that rarely need service.

Beg your pardon if it's just my poor judgement that keep getting the lemons.   What's your experience, and tips to keep OTL amps up and running happily?


bsimpson
billspecfoc
103 posts
 
Some years back I had the then most recent Atma-Sphere MP-1 preamp along with the MA-2 Mk 2.3 monoblocks.  They were driving Dynaudio Confidence C2s with the source being a VSE-modded Sony 777es.  The AS gear was the most transparent, fast, textured, layered equipment I have ever heard.  Everything just sounded right.

I also heard AS gear on the big (at that time) Sound Lab electrostats on a vinyl set-up. I can't remember what that vinyl rig was comprised of but what I do remember was it's total cost was in the neighborhood of about $50k.  THAT was the best system I have ever heard.

The only knock I had against Ralph's gear was the amount of heat they generated.  With the big monoblocks I had, I barely used them during the summer.  But the sound they produced was exquisite.  I also never had any problems with them.
roberjerman
4,319 posts
 
I have owned Julius Futterman H3AA Mono's since 1981. And a recently acquired Harvard Music H3 stereo. Speakers used are KLH Nines and Quad 57's. No reliability issues over all this time! Superb sound - more "life-like" than any other tube or transistor amp in my collection!
ct0517's avatar
ct0517
2,041 posts
 
What's your experience, and tips to keep OTL amps up and running happily?


If you are running higher wattage OTL amps (I ran 225 wpc) monoblocks. Try to make sure they are not placed in the same room/space as the house Thermostat; especially during winter, and especially if the room your wife frequents happens to be on the other side of the house.

Heat was a real issue. I don't recall a single multiple hour listening session where I was not shedding layers.  

atmasphere's avatar
atmasphere
11,633 posts
 
@c

The heat of an OTL is like it is with any other amp- the heat is based on the class of service rather than the number of tubes. The exception might be if you run an amplifier using 6C33s (OTL or not), which run unusually hot!

If our amps are on Standby, after a day of that you can easily grab a power tube and hang on without burns. But start the amp from stone cold take it out of Standby to full On and after a minute of operation, its too hot to touch!

If you had a solid state amp of 225 watts that run class A, you would find it making a very similar amount of heat!
ct0517's avatar
ct0517
2,041 posts
 

Atmasphere
See pics 20 and 25 on my virtual system for the otl's.
Unfortunately AudioGon does allow me to link the pics.
so
If I put a cooking rack an inch above the amps.
The Krell FPB600 will keep an X-large Pizza toasty ready to eat.
The previous OTL's would have cooked it for me as well.  

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