What commerical audio system tweaks provide sound quality improvement??

Quite right, Todd. I missed room treatment. Mea Culpa.

Assuming that you have a nice system which you like, you might want to consider the following. I save my money for the physics - that is, if and only if the physics is solid and uncontroversial. Then I have been known to spend real money.

Those areas are: capacitors (film and foil are the best), resistors (nude Vishays are best), solid connectors (not necessarily expensive, just solid), clean power, clean stylus, and clean records. And the most cost effective tweak of all: little rectangles of sticky jelly-like substance, which can be stuck on things to control resonance, Moongel, for $10. I use the stuff extensively on my air bearing tonearm.

You may notice some high-mark-up items missing from my list. So is everything controversial. That's how I approach the subject: physics first. YMMV

These are common on test equipment, which can be influenced by ambient radio noise because input signals can interact on some settings. For audio, not so much, although at the preamp, the tape out RCA's and amplifier RCA's can be connected. In that case, be damned sure that you don't use shorting caps on the tape out RCA's, which short the signal line to ground.

I suspect that the main advantage is cleanliness, which should not be under-rated.

@geoffkait  

Make sure you turn off the power at the breaker box before you clean the outlets. PLEASE !

Geoff, you would have to be cleaning ONE outlet, the hot one, with a material that becomes conductive, for one reason or another; e.g. wet with perspiration. That and a path to ground, no matter how elusive or invisible.

And Geoff, I did not insult you nor your intelligence, so pray do not insult mine. There is no need for that.

@geoffkait  "I never turned off the power prior to cleaning outlets and am fine. I mean except for a slight twitch."

Bad advice, Geoff, in my opinion.

Perhaps you know enough to do that kind of thing with some safety, but not everyone does. I suggest you withdraw that.

One does NOT need to touch both hot and neutral to get a shock. All that is required is an electrical path from hot to ground. That can happen innumerable ways: damp floor, kid spilling his drink, or any other innocent means of being in contact with a grounded object while cleaning.

Oh, and did you ever think of your kid emulating what daddy does? There is 2 horsepower hiding behind every receptacle, waiting to get loose.

I stand by my posts. PLEASE disconnect at the panel.

Yeah. Right.

Thanks todd, sunnyjim, and falcon. I was starting to feel a bit lonely.