If the lights are brighter enough to notice, your mains voltage must be pretty low. Have you listened to stereo with generator on?
Power conditoner..
I have a stand by generator for my house. I've noticed when we have an outage & the generator kicks on the lights in the house are brighter. They are getting a full 120v. Because of this I thought a power regenerator would make a big difference in my stereo. I installed a PS Audio Stellar 3 Power Plant & I can't tell any difference. Oh well, live & learn.