Aragon 4004 mk2 vs Adcom 555 mk2

Two things:

1. The feedback loop would not use a pot if the design is worth anything as the guy suggested. The switch, as a designers opinion, switches high-quality resistors in and out - doesn't use a pot so that argument is not worth reading. He is right - pots sound terrible, that is why they are rarely used or done so as to no affect the circuit.

2. The feedback switch is so that if you are using inefficient speakers, the amp will be stable with higher feedback. A zero/low feedback design can become unstable very very easily if the right (rather, wrong) conditions arise. So the switchable feedbacks are to match speakers - not correct sound. Arthur

If the feedback signal were perfect with regard to gain and phase it could only improve the overall performance of the amp. High amounts of feedback become a problem when the feedback is less than perfect, either because of circuit design or real-world component tolerances. "Too much of a good thing".

Yep, anything in excess is bad, feedback included. Yet, I don't understand the hang up that audiophiles have with feedback. When I say feedback, I mean GLOBAL feedback. It has a zillion advantages that any engineer can name off for you because in the rest of the electronic world, feedback is absolutely critical in just about every circuit I can think of. In audio, I don't think feedback causes any detriment to the sound per se. I have looked this up several times and the post Gmood pasted above has too many inconsistencies to be reliable IMO. Local feedback is present in 99% of amps. I talked to Nelson Pass and what he calls "zero feedback" means he has local feedback but no global. This is fine however no one ever seems to complain about local feedback sounding poor. Kind of funny that guys who buy zero feedback amps for the name are actually listening to high local feedback designs and proclaiming its benefits. An amp with no feedback at all, will crash and burn with most speakers. I guarantee it. I have seen it in the lab many many times. So, before complaining about feedback sounding bad, consider what I have said. There is probably an exception out there somewhere (meaning no NFB at all) but we probably wouldn't buy it due to audible oscillatory reactions with the speaker's reactance. Arthur

You probably have less problems with feedback phasing around one stage (local) than across the entire circuit. So in the real world, local feedback may be less problematical than global feedback, even if the net total dB is the same. In an ideal world, both would be perfect.

It is unfortunate that we use the word "Negative" to indicate polarity of the feedback. That word has negative connotations.

Im not an engineer by any means but I kinda thought that ALL products have to have feedback of some kind. But Ive been in arguments in the past where people are telling me their products sound "superior" due to 0 feedback, and that they can "hear" the difference between amps with feedback and amps with no feedback which I kinda felt was a bit flakey. Ive always thought that what matters in the end is how good the product actually sounds regardless of design,pricetag or "brand name".