You really should have your AC unit examined first, not to mention your wiring to your stereo. Lifted grounds and neutrals can do all sorts of fun things.
Ideally, it would be great to have an oscilloscope view of what was happening. For instance, if your problem was common mode, then an inexpensive isolating transformer would probably do the trick.
Among noise suppressants what I would expect would work well for you are the series mode surge suppressors available most commonly via Furman, some quite reasonably priced. They filter noise at 3kHz and above, a much lower frequency than most power strips which start around 100kHz or higher.
On the expensive side of things Richard Gray’s Power Plants would also work. The resonant circuits they use can be very effective in otherwise noisy environments. I just find them priced out of this world.
Of course, something like the PS Audio regenerators or (my favorite) PurePower units (designed by the same engineer as Jensen Transformers) should work.
Ideally, it would be great to have an oscilloscope view of what was happening. For instance, if your problem was common mode, then an inexpensive isolating transformer would probably do the trick.
Among noise suppressants what I would expect would work well for you are the series mode surge suppressors available most commonly via Furman, some quite reasonably priced. They filter noise at 3kHz and above, a much lower frequency than most power strips which start around 100kHz or higher.
On the expensive side of things Richard Gray’s Power Plants would also work. The resonant circuits they use can be very effective in otherwise noisy environments. I just find them priced out of this world.
Of course, something like the PS Audio regenerators or (my favorite) PurePower units (designed by the same engineer as Jensen Transformers) should work.