OTL or SET? Differences?


With my limited knowledge, I know that OTL is transformerless and SET is single-ended. But what are the main advantages and disadvantages of these two designs? How to choose matching speakers for these two different designs?

Currently I have an Atma-Sphere OTL amplifier.

Thanks in advance!

Otto
yu11375

Showing 1 response by jeffreybehr

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...
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