How do you know if you need a power conditioner?

I'll partially agree with Albertporter about conditioners as many just compress the sound.

I have not tried regenerators such as PS Audio so I can't comment on them.

I have used transformers in isolation and balanced setups that have given mixed results from worse to better. As isolation only and properly sized, they have not been any worse. Typically, a small isolation transformer would supply the CDP as backflow protection, in plumbing terms.

If you got noise coming from the speakers when the music stops, isolation might be the simple answer. Unfortunately, the problem may be more complex.

When my system reached a certain level of resolution I noticed that reproduction seemed much more natural and less tense after 5pm, especially during weekdays, and then even more so after say about 11pm or midnight. The involvement factor improved much more so than just implied by ambient noise differences. I added dedicated lines (2 X 20A and 2 X 30A) and still sensed a dramatic (to me) difference due to times of the day. Adding power regenerators rendered the differences of times of listening moot. I'm afforded after midnight purity anytime now. I'm certain that this may be fairly unique to my system due to condo living and which businesses share the power grid I'm assigned to. Also different component's power supplies would have varying suseptabilities to power quality. I feel this would be a good starting test to determine whether you need additional power conditioning or regeneration. As always YMMV.

I have a power conditioner in my system. I've read many pros and cons, primarily sonic considerations about them. I remain neutral as I truly don't hear a major difference in sound quality. Suffice to say, if it made a substantial change for the worse I'd remove it. The biggest benefit for me is that it accepts so many plugs and in essence just cleans up all that spaghetti and power strip nonsense I had going on for so long!;)

A friend of mine has lent me his PS Audio P300 on three seperate occassions and a large balanced power unit one time. I only used these devices for cdp and pre and had them for long auditioning periods. I could never discern a difference using either of these units, either positive or negative. The audio community sometimes makes me feel as if I'm doing myself a disservice by not using some sort of conditioner. But my findings are strengthened when I read posts' such as the one above from Mr. Porter. But, as stated, I'm sure in some situations they are beneficial. I am running two 20amp dedicated circuits...

It's so interesting to read the different experiences people have had. I agree with everyone, but also think it's important to investigate your own particular situation. I used to have a house here in central Tucson. The power grid I was on also serves the U of A and the (huge) U of A Medical Center. The power was always above 122 (usually 123V) and never a hiccup (except occasionally during thunderstorms when it just flat quit!)

So I'd never even thought about power devices. Yes, installing dedicated circuits made a big difference in lowered noise floor and bigger dynamics, and I quit right there (un-intimidated!)

2 years ago, I sold my house and now live in a 50 unit apartment complex ca. 1950. It's on the same grid as my former house. Without even debating the issue, I bought both the ExactPower units and installed them; the balanced unit, for the source stuff, is powered by the main regenerator unit. It was all fed by some nasty 15A branch circuit. It did sound great though, and I settled down to a life of processed power ;~((

Then, one day when labeling the (real fuses) in the fusebox, I ran across a 20A circuit that I couldn't trace to anything. With my adrenalin pumping, and a few mis-steps (read: electrical shocks) later, I discovered it went (ONLY) to an outlet under the kitchen sink, meant for a garbage disposer that was never installed! OH JOY!! ;~))

I bypassed the disposer wall switch, with soldered connections. Changed the wall outlet for audiophile grade. Cleaned and Caig'ed the fuse and socket. Then I made a 12 foot Belden 10AWG umbilical to the ExactPower regenerator and let 'er rip!

Result: Sounds as good as it ever did at my house (Note: my whole system only draws 450 watts at full bore)

Moral: Always label your fuse or breaker panel!

Cheers