Tube Watts vs. Solid State Watts - Any credence?

Ralph,
thanks for pointing this out - you're right feedback & output power are not related. I should have written that sentence differently pointing out that output power depends on the topology of the tube - triode vs. ultra-linear vs. pentode with the output power going progressively higher as one moves from triode to pentode.

10-11-15: Bifwynne
Thanks Bombaywalla. I really enjoyed reading the 1983 Atkinson and Messenger ......

welcome Bifwynne.
yeah, I figured it might be difficult to understand what was written in that patent application not only because of the material of the subject but also due to the fact that it was written in technical legal-ese that patent attorneys love!
I believe that the basic premise of the partial cathode-coupling in the ARC output stage is to reduce output distortion while reducing impedance in the output stage circuit at the same time. This technique also allowed the ARC amps to have a "complex load driving ability" (written in his patent application) which in plain English means that they could drive tough speaker loads (the types that exhibit crazy phase angles that flip between capacitive & inductive over the audio spectrum).

10-12-15: Frogman
I will let the more technically astute than I debate the technical side of this
issue, but experiences with both tube and ss amps have shown me that
there is much more going on than "a watt is a watt", or wether
the amp in question is driven into clipping and how it reacts to being driven
into clipping.

I'm afraid that a watt is a watt & it is the distortion characteristic of a tube amp vs. that of a s.s. amp that appears to give the listener the impression that a tube watt is more powerful than a s.s. watt. It is not.

I bought my first pair of Stax F-81 electrostats back in early '90's when my
system included a NYAL Moscode 600.

this makes sense - an amp that is good for driving dynamic cone type loudspeakers (Thiel) & magnetic planners (Magnepan) cannot be assumed to be good enough to drive an electrostatic speaker. Electrostatic speakers are effectively a large capacitor to the power amp. This model of a capacitor for an electrostatic speaker comes from the fact that you have a stator on either side of the rotor/energized thin film that effectively creates 2 parallel plates of a capacitor where one is the top-plate & the other the bottom plate. Both stators create either the top-plate or the bottom plate. If the electrostatic loudspeaker looks like a large capacitor to the power amp, it also means that the impedance of such a speaker follows a 1/f profile i.e. speaker impedance is very high at low freq & very low at high freq. Just the opposite of a cone type speaker or even a magnetic planar. Since the electrostatic speaker's impedance is very high in the bass region, guess what?, the power amp has to pump current into a high impedance at the bass freq. Any s.s. or hybrid amp (which acts like a constant voltage source) will reduce its output with increasing speaker impedance. No wonder your NYAL Moscode 600 sounded horrible with an electrostatic & it was totally expected. A tube did much better because most tube amps act like constant power sources constantly adjusting their output current & output voltage to keep output power constant as the speaker impedance changes. This also means that a tube amp can give you relatively constant power (20% variation can be expected) over the 20Hz-20KHz range while a s.s. & hybrid amp will decrease its power into a higher impedance speaker load. it is no wonder that the Dynaco outdid your NYAL hybrid amp. Totally expected.
You have to be very careful which amp you connect to an electrostatic speaker due to the speaker looking like a capacitor to the power amp. Most power amps oscillate & self-destruct when they have to drive large capacitive loads.
It is no coincidence that SoundLab customers use tube amps almost exclusively (I think a lot of them use Atma-sphere amps) & that Sander Sound Labs makes a special s.s. amp for electrostatic speakers.

A watt is a unit of quantity and all are the same, but each case is different regarding the characteristics of each watt produced and how it sounds. Same amp can perform radically different with different speakers.

So saying a watt is a watt is true in theory in terms of how much power is generated, but in practice, all watts will be different sounding case by case. So there is certainly credence in saying that and value in knowing it, but alone it still determines only one piece of the puzzle in practice.

Are you trying to tell tube/solid state amps measure RMS differently?