What power conditioner will help in my situation?

Just shut off the fan when listening to your stereo!

I turn off the AC or heat, due to fan noise and circulating air, when I listen.

"I turn off the AC or heat, due to fan noise and circulating air, when I listen."

I guess many of us do. I do, but there is that other problem, "Is your refrigerator running?" which despite the old joke many of us do wish it would runaway considering the disturbing noise these modern refrigerators make. Smaller homes where listening spaces are in close proximity to kitchen is real concern, for unlike AC/heat shut off at thermostat, shutting off a refrigerator full of food invites real risks.

Aperez -

a dedicated line to your system would be the best option.

I had that same problem before I put in a dedicated line. The switch for the ceiling fan was one that allowed you to increase or decrease the fan speed. I changed the switch to a simple on/off switch and the hum disappeared.