OTL or SET? Differences?

You are one lucky and/or smart fella. Not many of us are blessed with OTLs. (Lifetimes ago, I had a pair of NYAL 'Futtermans'.)

OTLs, I think, are noted for their cleanliness and neutrality. SETs are noted for their musicality. I know this is a vague description, but for some reason SETs seem to retain more of music's harmonies; what they produce simply sounds more like music. SETs generally are lower powered, having by definition only one output tube, and hence are well suited to driving high-efficiency speaker systems. OTLs, because of their relatively high** output impedance, are not well suited for driving speaker systems that are lower than around 8 Ohms impedance or that demand high currents. High-ouput SETs have to use relatively large and exotic output tubes that often use VERY* high rail Voltages. Even my relatively common 50-Watt ASL Explorer 805s use over 900-Volt rails.

I wish I could find an affordable 150-Watt SET*** to use with my Eminent Technology 8s; meanwhile I continue to love the sound of ASL Hurricanes in triode driving the MR and tweeter panels of those 8s. Maybe I need a pair of all-triode 140-Watt Atma-Sphere MA-1 MkIIIs with their 5-octal frontends and FOURTEEN-6AS7-triode output stages.

* as is lethally high.
** sand-amp lovers probably would call that 'astronomically high'.
*** If, and I do mean 'if', an SET is the ultimate amplifier of music, and if that glorious rightness is due to several factors including 1. the use of indirectly heated tubes, 2. the use of only triodes, 3. the use of no paralleled tubes, and 4. certainly no push-pull operation, then my ASL 'canes, even running in triode, commit sin numbers 1, 3, and 4. The Atma-Spheres, too, commit those same 3 sins but have the benefit of not requiring output transformers. Hmm...
.

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

Duke, you are right. What I have is Atma-sphere M-30 and it is part of my second system which is for chamber music listening. The project is for my main system as I am experiencing slightly hearing loss on my left ear. That is the reason for me to change my Thiel 3.6 to speakers with high efficiency. I DO love the bass Thiel 3.6 brought me for the past 5 years. Yet I put lots of effort to tame its metal tweeter with little success. I also owned Silverline Sonata I around 4 years ago but the bass from Sonanta I just not enough for me while I listen to Mahler's 2nd symphony or some organ music. Please provide your suggestion.

Thanks!

Otto