Apparently the standards on mains frequency are going to be loosened in the US. No articles I can find give actual numbers or specs, but apparently it's something like instead of steady 60,00Hz it will be 60Hz +/- something. Again, I can't find any actual numbers in any articles except dumbed-down ones like 20 seconds per year (as if that told you anything useful).
What audio equipment could be affected by this? Most modern/commodity stuff has switchmode PSUs. Amplifiers with regular power supplies won't care about mains frequency, although there could be some extra harmonic content in the mains (again, it sure would be nice to have actual numbers).
Does anyone here know anything about Technics turntables? I have an SL1600 that has a strobe for you to adjust the speed with, but I don't know if the strobe itself is sync'd off the mains or of it has its own crystal source. And I don't know if this turntable speed itself will change if the mains frequency changes. I used to have a cheap Marantz turntable that had a synchronous motor. A turntable like that would definitely be affected by mains frequency. Most of the high-end-belt-drive turntables use servo or stepper motors so their speed won't be affected. But what about Technics? Can you think of any other audio gear that depends on a steady mains frequency?