Mine used to when I had a Pass x350. I don’t think I had a direct line for the amp at the time. I kind of liked it. It made me feel like it was really powerful.
I now have an Audio Research Ref 160... no dimming.
Do your lights dim when your amp powers up?
Mine do. Even though I have a home electrical system that is only 15 years old, a separate 20 amp breaker, 10 gauge line, and the amp plugged directly into a medical grade outlet.
Do you have this issue? If so, do you care about it, and is there any chance that it is affecting the quality of sound?
kn