How close to the real thing?

Atmasphere, unfortunately the way you present the concept of feedback with the term "propagation delay" helps to 'propagate' (sorry, couldn't help it ... :-) ) a misconception about negative feedback. Yes, "negative feedback is always lagging behind" but it is still able to "correct the signal it was supposed to". If it ends up lagging by 180 degrees, half a wavelength, with gain still happening, then you have positive feedback, and an oscillator, and fried tweeters!

So, the feedback ALWAYS lags, even by some tiny amount, but that is just part of the understood design of any working circuit. You can easily buy one of those "terrible" opamps with much more global feedback then a typical audio power amp, that is working comfortably at microwave frequencies, that is, beyond 1,000,000 kHz -- not bad for such a "mediocre" part!

Global feedback in an audio device, on the other hand, with discrete components is typically rolled off (because it has to be for stability, remember the oscillator!) to become non-existent at the higher frequencies, where it is most necessary, and where the ear is most sensitive to distortion -- that is part of the real problem. Also, that is why nearly all gear has rising distortion at higher power, and higher frequencies; in other words, it is not the presence of feedback that's the problem but that at the very time it is most needed, it's done a bunk ... :-) !!

Frank

Frank ,

The time smearing can be significant, this is what Atmasphere was alluding to, I do believe this is so if one get's carried away with NFB. Most SS designers today understand such and dont drink from the NFB pond in excess. The only way to eliminate it's usage is to design amplifiers which are very stable( matching transistors goes along way here) I do Believe Nelson Pass has made an even bigger step and acquired some pretty interesting devices, so we will see.

Tube amplifiers also use less NFB than there SS counterparts, so if NFB is really,really, bad then.....:):)

IMO output stage Bias is also very important in creating "that sound" associated with SS amps, how you balance the 2 ( Bias amt/NFB) when attempting to reduce distortion gives the amp that certain SS "character".

Regards,

Sorry Weseixas, re ".. can follow along ...". My earlier comment was just firstly agreeing with Kirkus that a lot of people have had special listening moments without it quite making sense why, and secondly, that my answer is to be fussy, fussy, fussy, just like people who make and look after aircraft are, which is why flying is so relatively safe, ie. equivalent to audio sounding "real".

Frank

Hi Frank, opamps usually have much lower propagation delays than power amps do! So feedback is more effective with them.

To improve the effect of feedback and decrease the resulting odd ordered harmonic generation, decrease the propagation delay of the circuit.

Irvrobinson, while our amplifiers tend to have higher output impedances, that impedance curve is nearly identical to the frequency response curve of the amplifier, IOW linear from 2Hz-100KHz.

The system was entirely solid state. The format was a digital reel to reel, 1/2" wide. I really did not hear the system, it was only the experience of the music. So what would it have been like if it was 2" analog with my amps on each speaker? Hey, maybe it would have been better.

Atmasphere, I'll admit I don't quite know what to make of this. Although I respect that you have sufficient confidence in your design approach that you feel your products could ALWAYS make a subjective improvement over anything else, it seems that your judgement (or at least your recollection) of this particular experience is totally dependent on your knowledge of the technical matters of its presentation.

This is what I would call a "Maggie Blackamoor" conclusion, after the character on Little Britain: http://www.youtube.com/watch?v=hUpHDtpoY9w

But since I brought up the subject of scientific philisophy (and also to avoid at least a bit of the well-trampled "NFB argument" road). . . to be a bit more precise this would thought of as a plainly "coherentist" argument. That is, the truth or validity of a given conclusion is based upon how coherent it is with an existing perspective or set of beliefs. For the coherentist, the method by which a theory is refined (made more precise) is when data is presented that incoherent with the current belief system, the belief system is revised to restore coherence with new data.

But the logical problem is obvious, it's the same with all theories of justification: it fundamentally relies on one's intellectual "concience" to formulate ideas that evolve beyond one's own belief system. In the field of audio this is particularly problematic, becuause our understanding of many of the perceptual and psychological mechanisms lags far beyond our practical understanding of the physical science on which our technology is based . . . technology that we so routinely use to (attempt to) fool these perceptual and psychological mechanisms.

But we can also see from this line of reasoning that the traditional audio "objectivist" arguments have NO better grounds in modern scientific practice than the "subjectivist" . . . they are both in actuality simply "justificationist". It's simply that "objectivist's" belief system usually can't include a reality outside simple regurgations of common-practice electrical analysis found in an average undergraduate EE textbook, and the "subjectivist's" belief system is so fundamentally undisciplined as to be able to include some really silly, wacky sh*t.