Are all amps being built wrong?

Ralph (Atmasphere) posted: 

If you add a resistor to the output of a solid state amp it will indeed simulate some sort of tube amp that uses feedback. Most transformer coupled tube amps with 15dB of feedback will act as a pretty good voltage source. You might have to play with the taps on the output transformer. Between Voltage source and Current source there is Power Source, which is how a tube amp will behave if it has no feedback or if it has voltage and current feedback of equal amounts.

I think Ralph is right on.  My ARC Ref 80S is a transformer coupled tube amp that uses 14db of negative feedback.  And I do **play** with the taps to get the best sound.  At this point, I have settled on the 8 ohm taps, which I believe have an output impedance of approximately 1 ohm.  The DF is 8 if the amp is coupled to an 8 ohm speaker off the 8 ohm taps.

As to comments made by others, I believe that it is correct to say that matching my amp (or one like it) to a speaker that was designed and voiced to be driven by a constant voltage source amp is a bit of a tone control.  To some extent the amp's voltage output will vary to some degree as a function of speaker impedance, which in turn, will vary with frequency.  

All that said, I like the sound of my amp/speaker combo, ... tone control and all.  Ironically, I surmise that between room affects which probably boost the bass a bit and and the tone control affects of the amp which soften the tweeter/high frequencies, the overall frequency response and sound is musical and pleasant.  Just my opinion. 

BIF

@atmasphere 

Ralph, quick question on negative feedback (NF) distortion.  I seem to recall that Audio Research output stage coupling is a combination of "Ultralinear" and "partially cathode-coupled" topology.   I have no idea what that means.  I clipped it from a Google search. 

Does that type of feedback create the same distortion as the type  of NF used in solid state amps or is the distortion still there but tamed to some extent?      

@atmasphere 

Ralph, thanks for the info.  I recall that many years ago you explained that global NF creates temporal intermodular (TIM) distortion because of the infinitesimally small amount of time that it takes for the signal (after phase inversion) to loop back from the output stage to the input stage.  That small time delay causes TIM distortion, ... if I recall your explanation correctly. 

Perhaps in the case of "[u]ltralinear" and 'partially cathode-coupled' topology," the physical distance is shorter because the local feedback loop is shorter.  Just a guess.        

@atmasphere  ... thanks Ralph.  I would be fibbing if I said I understood everything you just posted, but at a high level I can appreciate a little bit better why feedback is used and what its limitations are.

Too bad our hobby is really a business.  What I mean by that contradiction is that it would be interesting to compare various types of amps (e.g., zero feedback, some feedback, solid state, tubes) in a controlled environment with the same speakers at the same time.  That is the hobby part of our musical pastime.

The business part is that, IMO, it is unfair and unrealistic for one to think that they can sit for hours on end in a brick and mortar store, take up a salesperson's time comparing amps, ... and then not to buy something.

Thanks again for the great posting on feedback.  It shows that a lot of thought and experience goes into designing and manufacturing really good audio equipment. 

@holmz ... I agree with your last 3 sentences.  As to your 2 bullet points, ... sure, try to spend time educating your ears, switch gear in and out, burn sales people's time.  If the sales people think your not a buyer, they will toss you. 

IME, it takes time to listen to gear, switch stuff in and out, and so forth.  And even then, unless you are switching gear in and out of your system, ... in your home, there is risk that what you think sounds good in the store may not sound so good when you get it home.      

That is why I read reviews and buy brands that I trust, like ARC.  So far, I have been lucky.  But I will never know if I could have done better because I don't sit in brick and mortar stores comparing gear.  I simply don't feel comfortable.