Device for voltage at 120

I have troubles with tubes being damaged and believe its from voltage changes. I have amps and cd players that turn on by themselves. I was told it is from that problem. Is there anything I can do to keep the voltage a constant 120
Look on Ebay for a Tripplite line stablizer/conditioner(LC). These come in 600-1200, 1800, and 2400 watt sizes and are dirt cheap by audiophile standards; <$100.00 for a LC-2400; <$40.00 for a LC-600.

These things use a heavy autotransformer to keep voltage within a couple percent of 120. Sounds like what you need.