Atmasphere amps trustable?

Unfortunately, my experience with my M-60 was not all that great.  I bought it new about 4 years ago through an authorized dealer.  Within the first 3 months, 3 output tube failures. Every time a tube failed, I would hear a loud pop through my speakers scaring the c***p out of me.  Tube hiss was another issue.  Power transformer hum was another.  By far the noisiest tube amp I've owned. After 6 months, I sold it and never looked back.

On the positive side, it had the best high frequency I've ever heard from any amp.  Smooth, crystal clear, and detailed.

B: I hear you, thank you.

When I encountered the OTL concept for the first time and read about Futterman's early efforts along with a few editorial accounts of experiencing "sonic bliss" but with the acknowledgment of some (potentially tube only-based) unreliability issues, I researched more and learned about a design that seems to make sonic sense on paper, and in some critical listening, but has challenges matching optimally to the impedance spectra of many well known and popular speakers. Still, the ability to make it work reliably and sonically is cited to have improved even though the ~4 Ohm output impedance still seems to a limiting factor; it's difficult to apply the ten-to-one minimal nominal speaker to amplifier impedance ratio often cited in order to maintain flat frequency response.  

I would love to hear an OTL based system properly set up. So, perhaps while I don't know what I'm talking about either, I am interested in hearing from those with real experience owning and living with OTL amplifiers. I also agree that to jump to a critical stance without knowing is not the best choice, but I am humbled by the experience and expertise of others to help enlighten. 

Been reading about Transcendent’s products. I want to build one (or two monos)!

Tubes are retro of course from the beginning.
They're noisy, require LOTS of wall power; generate LOTS of heat(especially OTL ones!) and LOTS of distortion(even considering even order ones) making the playback far from real. Very often the soundstage will seem like sounds from far away. Also as tubes about to become bad, these unpleasant effects multimultiply including some unwanted echo, RF or EM interference or microphony. Tube components indeed sound different, but they're just toys and nothing serious no matter of reputation or credibility of one or another manufacturer. 

Stevecham 8-4-2016 10:34 pm edt
... the ~4 Ohm output impedance still seems to a limiting factor; it's difficult to apply the ten-to-one minimal nominal speaker to amplifier impedance ratio often cited in order to maintain flat frequency response.

Many and I believe the majority of tube amps of all kinds will not meet that criterion.  For an 8 ohm speaker it would imply a damping factor of 10 or more.  Most high quality tube amps seem to have damping factors somewhere between 8 and 2 (with some being even lower than that), corresponding to effective output impedances of between 1 and 4 ohms or so, respectively.  (Audio Research and McIntosh tube amps are among the minority having DFs greater than 10, just a bit more in the case of most ARC designs and as high as the low to mid 20s in some McIntosh designs).

As you recognize, the 10:1 ratio you referred to will assure minimal variation of the amp's output voltage as a function of variations in speaker impedance over the frequency range.  However meeting that criterion is neither necessary nor desirable in many cases.  Assuming that the particular speaker does not require a higher damping factor for woofer control, meeting that criterion will be unnecessary and/or undesirable in the following cases:

1)The impedance of the speaker varies relatively little over the frequency range.  In that situation the amp's output voltage will vary relatively little as a function of frequency even if the ratio is much lower.   

2)The impedance of the speaker is relatively high at all frequencies.

3)The design of the speaker is such that the variations of the POWER it receives as a function of speaker impedance variations over the frequency range should be minimized for best sonics, rather than variations of the VOLTAGE it receives.  See Ralph's paper on "Paradigms in Amplifier Design."  While such speakers are in the minority, there are many such choices that are highly regarded.

4)Cases where the load impedance seen by the amp can be raised to a suitable level via a Zero autoformer.

Regards,
-- Al