Power Conditioners: Myth, Magic, or Necessary

I do know from experience that, as others above have attested, different components will benefit to differing degrees from AC power tweaks. Your amps simply may not need this treatment to sound good. Or, your system (or ears) could be failing to inform you of the differences, which can range from large down to subtle in nature. And then there are always the matters (as was also mentioned above) of *which* PC you're using, and how contaminated your AC is in the first place.

So I'll just bring up two things additional here. One being that, other than your AC quality straight out of the wall, there's also the issue of stray environmental RFI/EMI to be protected against, and the possibility exists that in your particular location and system, this may simply not be a big problem. The other thing is that in many instances, it can be source components that will reveal the most benefits from an upgrade PC, so before you sell the cords, you may want to try them out there instead just for grins.

I have found that filtered power, and especially balanced filtered power, can and does make a positive (though not life-changing) difference, particularly on my digital front-end, so you may still want to try a PLC out. But after all is said and done, I agree with Tim and the others - if you can't hear an improvement, then be all means get rid of 'em and just enjoy your music!

How to decide if your system needs conditioning is the big question. Some thoughts:
1) If you see an improvement late at night.
2) Turn your volume up with nothing being played. How far do you turn the volume before hearing "white noise"? In my case I hear nothing even inches away from my speakers until the 12:00 o'clock on the volume. Since I listen at 8-9:00 them EMI/ RF is probably not a problem.
3) Try a "noise sniffer" sold, I think, by Quiet Lines or Audio Prism. If this thing has no noise probably not in your system.

Vrsola, you can get a mini-stealth for $499 from one of A-gon's "approved dealers". I forgot which one. They normally retail for $599. It is a 2 outlet version of the Stealth and the mfg'r told me identical in every other way.

Cdchas the right test. I am able to turn the volume up 100% and hear nothing 3" from the speakers. Just for fun I tried plugging everything into a standard outlet with stock cords and at 50% volume I could hear a whooshing noise from my listening position.
As far as the scam of power cords and conditioners, I have come to believe there is a lot of products out there that do little to nothing. I have tried a great deal of power cords and conditioners, and it's the power cord business that I most suspect. I found very little of true improvement in the $50-$700 price range. Most of the more expensive cords I tried di indeed help.
I live in a very quite suburb and receive my power from a pole mounted transformer 50' from my house. I am the only user on that transformer, so if it's possible to get great power I've got it. Power cords, dedicated circuits, outlets and conditioners all help my system. As the system has improved and become more detailed, the need for clean power increases. Perhaps the people who hear nothing have larger issues to address first.

power conditioners
contd
Some basic things which I ignored.
(1)One day I saw the ground connection for my TV cable was broken.This was done by the lawn mowing service person.

(2)The Power cables, speaker cables,Interconnects which I separated them, and elevated from the carpet are on the floor,parallel to each other probably dislodged themselves as they are stiff or by my spouses cleaning efforts.

all the above 2 I corrected promptly

I also obtained a cheap quantum clear power module(about 40 dollars from an audiogon dealer) and connected it to the TV.
Instead of using 2 wall outlets, I used a third one near by.
Now the TV picture is also close to the picture at the late night.The audio also improved significantly,closer to but not exactly the same as late night listening.

The only thing I can say is- Start from basics, check them frequently( cables, ICs, ground etc)
separate digital components including to TV,DVD, CD, DAC and the Cable Box to another outlet and power cleaner.
The quantum power cleaner for 40 dollars is fine and it works.at least for me in TV.
regards