Thought on OTL tube amps

With my speakers, Merlin VSMs, the Atma-sphere M60s have proven to be the best all around amps for my taste, up against a few amps I have had in rotation in my system, the best of them being the CAT JL2, Pass XA30.5, First Watt Aleph J, Music Reference RM Special Edition, and Quicksilver V4s - that is, for me the OTLs produce the best sound up against some of the very best tube and SS amps made - though the Music Reference is right up there, and have no doubt that with more difficult speakers might edge out the OTLs, but with proper matching (not hard to do) OTLs are pretty tought to beat. I would put the Joule OTLs right up there with the Atma-sphere, you cannot go wrong with either IMHO.

A good OTL has the immediacy and presence of a SET amp while generally providing even better bass response. You will also hear a lot of people using the word transparency. OTL's have a liquid yet very neutral and open sound. I love both OTL and SET amps. I own an Atma-Sphere S30 as well as 45, 2A3, 300B and GM-70 SET amps. I would not part with any of them. To my ears the SET amps colour the sound more than an OTL does but the sound is so gorgeous I don't care to be a purest. I find I use the S30 OTL and GM-70 the most. They have more power than the smaller SET's and I find they are also better balanced - not unduly emphasizing the midrange like the 300B does (which can be wonderful in its own right depending on my mood). I think all audiophiles should experience both a SET and OTL amp as a right of passege during their audio journey.

I'm sorry, but OTLs can't begin to match SET amps on the right speakers. That being OTLs on the right speaker as well.

Ralph,
If you would address speaker load, I for one would be interested. I can express my preconceptions but it would be better just to have the subject addressed in a broader way. I can say that I would love to try some OTLs on my speakers (four way, horns for top three and isobaric woofer configuration on bass). Efficiency for woofers vs horns is about 8dB different and I am pretty sure the high three are padded down the crossover. I think the mids and treble (104dB) have a relatively high impedance but I expect the isobaric bass (96dB) may dip as low as 4 ohms (I remember reading that somewhere). I need about 30W or what I think is significant damping on the bass. My 13W EAR 859s just don't cut it on the bass, and my 8W AudioTekne PP 2A3 amps produce almost no bass.

Would an autoformer allow the low-power tube amps and an OTL to work?

Almost all of the OTL amps I heard had an incredibly appealing immediacy and liveliness that solid state never has and most tube amps also also lack. That comes with a bit of a touch of roughness with certain recordings (particularly classical music). Several models I heard also seemed to have a bit more tube noise than other kinds of tube amps that might be an issue with extremely efficient speakers (a friend sold an M30 because of noise with 107 db efficient speakers. I thought that was a mistake).

A really good SET amp can also have similar kind of liveliness and immediacy. But, low powered SETs are much more limited in the models of speakers they can be matched. Although OTLs are expensive because of the amount of wiring needed for the multiple tubes, really good SETS can be even more expensive because they demand a top quality output transformer. For the vast majority of applications, I like OTLs.

Personally, I run 99 db/w speakers with a parallel 2a3 SET (two output tubes per channel), but, I don't play my system that loud.