• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

60Hz/220V??

A bit surprised about the 220V/60Hz made in Britian. The standard there is 230V/50Hz. Britian used to be at 240V/50Hz, but they changed to be in line with the EU. In actual fact they didn't change a thing, their generators still put out 240V, but this is within the spec of 230V +-10%.

So the voltage of the unit will be no problem.

With the frequency again there should not be any problem. Btitian uses 50Hz standard and any transformer they use at the input of the power supply should run at this frequency. If the transformer was designed for 60Hz, it will still work, just be slightly more ineffiecient.

Cheers
 
The tube should work fine but since the ac supply is lower by 10 volts the power of the amp would be effected. This is because the voltage after transformed would be much less( 10 volts times the ratio of turns). For 60hz however the caps has less work to do as the ripple voltage would be smaller. COuld be a problem were the amp works but not to what it was designed for. As zener diode used for reference might be wrong. Just giving you some examples. You have to look in the amp to see how it was built. Also less voltage you are running the tube at a lower current.
 
There seem to be 2 possibilites:
Either it's a mis-print, in which case ignore it.
Or, It really has been built for 60Hz. In that case the mains transformer will not be suitable for a lower frequency, it will be too small, and might have a high energizing current at 50Hz. It will probably get too hot. This is more of a problem than the smoothing caps, which can be added to.
Who is the maker of this amp? You should check with them, or someone who knows of them.
Regards
John