Having a steady 120 volts is fine for almost any modern gear. There is some old vintage gear from the 1950's and 1960's that supposedly work better at 110 volts (I know people who use a variac for that), but, mdoern gear should be built to work with 120. In my area, I have seen spikes above 130, and someone not to far from me measured spikes close to 140. A friend of mine had a Tron tube amp that failed repeatedly. It was always the solid state part of the amp (bridge rectifier), and the manufacturer replaced the diodes several times before he finally decided to source beefier diodes for the repair; the manufacturer said he was unaware of how widely the voltage swings in the US and did not account for this. I read that an ultra expensive Japanese solid state amp made by Technical Brain also constantly failed in service in the US but never in Japan. It turned out that Japan has rock steady voltages and the manufacturer assumed the same for the US. It appears that builders in other parts of the world are slow to pick up on something we living in the US are aware of--the US is rapidly slipping into 3rd world status.
