Thought on OTL tube amps

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.

Most OTL amps to me sound lean. If you like this transparency you can have it. Go listen to live music then you will know.

Jwm you mention that most OTL amps sound lean to you. Have you listened to any of the Joule Electra models? It seems that Jud Barber has somehow managed to capture the harmonic realism so apparent with most SETs without any loss of transparency, the best of both worlds.

In my experience the perceived limitations by some concerning OTLs rest elsewhere in the system providing the speaker impedance/amp are a good match. A poor recording will really highlight problems more so because of the wide bandwidth performance of OTLs.