SET vs OTL

@pani,
’Even a large instrument like Cello, when bowed has a very direct and focused sound, like it is speaking to you. Only SETs get this directness. Is it because it just amplifies without any further "processing" ? May be.’

Yep! Precisely my same reaction with initial listening exposure to a SET amplifier. In a nutshell,  more real, more natural.   Different people hear and are drawn to various things when listening to music via home audio. There is not a single topology that gets everything right, no perfection. So people resort to choosing what comes closest to sounding ’more’ right than other available alternatives. So it may be SET, OTL, class A solid state, class D or whatever. SET for me and something else for somebody else.
Charles

How about an OTL SET ?

I don’t think it is possible.  The tubes in a SET amp are constantly outputting dc that is the modulated up and down in output by the audio signal.  That changing output fed to the primary windings of the output transformer then induces an alternating current in the secondary.  Absent a transformer, a SET amp would be sending a very large dc signal to your speakers, particularly when there is no music playing, and dc is very bad for speakers.

Could a DC offset protection circuit be used to make a OTL SET?

No, it would constantly be in protection mode, meaning no output.