SET vs OTL

In a nutshell, hypothetically, if the speaker is a "very easy drive without any hindrance" at all to either amp, the OTL in class-A will be the better amp full stop.

BUT!! for an OTL not to be hindered IN ANY WAY at all by todays "better sounding speakers loads" that have NOT had "their sound compromised" (because they were designed "firstly" too give a very easy load), is a big ask.
And those type of "very easy to drive speakers" usually have big other glaring problems to many listeners that are susceptible to their colorations,  so it’s a bit of a catch 22.

Cheers George

The autoformer used as an impedance matching device is, in effect, an output transformer.  It is doing exactly what an output transformer does.  To me, if something sounds good, I don't care how it got there.  I've heard many great tube amps, and I would not dare to say if any particular topology beats out another.  My personal favorite happens to be an OTL amp, but, it is an utterly unique, one-of-a-kind design.  A very close second (maybe not even second) is a pushpull amp that is extremely rare and costs six figures for a pair (Western Electric 59A).  I own a pretty good SET amp (Audio Note Kageki) and I've heard many other good SET amps, but the amp I currently run in my system is a low-powered pushpull amp.  

I know the Duevel line fairly well. What I would like to know is how low the impedance actually goes and with what type of swing. I agree that using an auto-former somewhat defeats the purpose of an OTL and would not be an option for me.

For the record I have heard Atma-sphere, Joule Electra, Berning quasi-OTLs, the older Tenor, Transcendent Sound and Einstein. 

I also have auditioned/owned several P.P. designs from Thor Audio, VTL, EAR, VAC, French company I cant remember that was famous for CD players and SETs using 845s, 2A3s, 45 and 300Bs. Granted no SET design that was over $ 20K. 

I believe that each type of amp share many similar sonic characteristics. But removing the transformer is always a plus if you can feed the amp its entre of choice. 

The best SET amp I have heard was an old Mastersound made 32B integrated amp running only an an amplifier.

@audition_audio,

the higher the impedance, the better for OTLs. On the Graaf, the autoformers gave a marked improvement to going without. Old speakers used to be 16 ohms which would be ideal for OTls, however most modern designs have impedance dips under 4 Ohms with which OTLs have a hard time The Duevels in this regard are relatively benign and an easy load.