Anyone runs Euro voltage power amp or integrated with transformer ?

Frequency converter will though. 

I ran 2 Cayin integrated amps for several years on a cheap upconverter. Bought both in China so 220V 50Hz. No issues. Currently still running JL Fathom sub I bought in China with upconvertor. No issues. 

I would use what looks quite good acupwr.com transformer.

I've had no hum or any other anomalies. Still always kinda bothered me in the back of my mind for some reason. Tried to get them switched but nobody wanted to mess with it in my area. 

This wouldn't bother me but I would not use cheap Chinese transformers, that's for sure.

Why  would you want to use a transformer in the first place??

Example is Gryphon. They said they wouldn't convert to North American voltage, and there are many more Gryphon pieces for sale in Europe than here.

I think you can get away with out the frequency converter if its just an amp and preamp with no digital or clocks. then just the step down-up. I ran a Luxman L560 Japan only Integrated on a step down TX for a couple years worked great, so did the amp. The amp even said 50-60hz 100vac.

Turn table with an ac motor would be affected by frequency. 

No , no digital.

I thought this too about turntable motors, but I may only need it for amps or integrated.