IMO, well-designed equipment should be OK with 10% high AC input voltage.
consistently running a bit high on the voltage may be indicative of a problem with the power line neutral conductor (most homes have both 120V / 240V single-phase service). have your local power company check the drop from the pole to where it connects to your meter socket. also consider having an electrician loosen then re-torque all connections inside the breaker box including the neutral bus. a poor neutral connection can cause noise spikes from motors / appliances on other circuits within your household to be coupled into your audio gear.
often the utility company's drop from the power pole to the house contains splices in the black "hot" conductors which are then purposely slacked to provide some spacing between the splices and the bare neutral wire. So the neutral wire winds up as the only conductor in mechanical tension and supporting the entire weight of the drop cable, and the strands can break slowly over time near the splices...
room lights getting brighter when an appliance is turned on / dimmer when an appliance is shut down might be indicative of a neutral problem.