Is dirty power the culprit?

I would guess both power and the human factors cited above are likely culprits.

It could also be you just don't like your present system. I've had similar feelings about systems over the years, I'm finally at the point where I like my system all the time. While I may not enjoy it to the same level at each listening session, I never end my sessions feeling something is fundamentally wrong with the system, now chalk it up solely to mood/disposition variables.

well, for what it's worth, i live in boston as well and have experienced similar differences with my systems that i attribute to the power.

oddly, the evenings in boston seem to be the worst times for power. often things sound pretty good to me in the morning and early afternoon, but get noticeably worse in the evenings -- until 1am or so.

and it does seem that some days are worse/better than others.

oh well. i just deal with it by listening to better-recorded material or by just watching tv. flight of the conchords sounds funny with bad power or good...

one day the system sounds so wonderful you are convinced you do not need to change a thing in your system and are set for life. Then the following day or a couple of days later the system sounds like a collection of items purchased at toys are us.
Montepilot (Threads | Answers)

Montepeliot, what you describe are *extreme* swings in your evaluation of your system's performance, not marginal ones. Don't allow anyone to suggest to you this is some psycho- acoustic phenomenon, tied to your mood or emotions, or state of mind at the time. These swings in performance are tied to the AC. Other than dedicated lines, which you cannot do where you live, I really don't know of a conditioner or regenerator to recommend. My attempts with the PS Premier were a failure (it did more harm to the sonics than good in my setup) I did try the APS Purepower regenerator and I'd like to try it again. For me it beat the Premier. I'd still have it if not for a glitch with the backup batterty. If only we could isolate our equipment from the power grid altogether and have pure clean power! Then we could hear what the gear is really capable of. That would be ideal!

These swings in performance are tied to the AC.

I always admire the way that vague symptoms in a nine line post (sounds "wonderful" versus "collection of items purchased at toys are us") can be diagnosed by others with such unquestioning certitude even though they haven't seen, much less heard, the system themselves.

It would like phoning a doctor who has never seen you, complaining of generic symptoms, and getting a precise diagnosis.

Power line issues can cause problems but it is hardly the only cause. Several avenues of investigation have been suggested to the OP. I hope he finds one - or a combination of them - helps with his problem.

While I am a firm believer that the listener is a major variable, and that often differences will be perceived when nothing whatsoever has changed (including the recording), I think that if the differences here are as great as you seem to be describing, something else is going on.

I'd suggest first that you buy or borrow a multimeter, and measure your line voltage on the good days and on the bad days. Also, take an AM portable radio, tune it to an unused frequency near the bottom of the band (e.g., 540kHz), set the volume level to a repeatable point, and compare how much rfi it picks up when placed near your power cords, on the good days and the bad days.

That will address (at least roughly) two of the four ways I can think of by which power might be affecting your system (voltage and noise). The other ways would be harmonic or other distortion, and dc offset, but you would need more specialized equipment to address those factors.

Beyond that, my bet would be (as Mapman suggested) that you have an intermittent problem in one of your components. Perhaps a capacitor that is leaky and on the verge of breaking down. Perhaps you can borrow some other component(s) to swap in on the bad days.

Regards,
-- Al