Cycle Conversion

Krell's power transformers are already set up for 50Hz. So the real issue is line voltage. If you are already set up for that then there is nothing else you need to do.

Lower freequency will certainly dictate lower RMS of already rectified voltage.
Why am I using the term RMS is because at the output of the full-wave or half-wave rectifier(whichever applies) there's still a pulse that needs to be smoothed by electrolytic capacitor. The value of such capacitor is being selected depending on the timed distance and certainly an amplitude between sine pulses at the output of the rectifier so to make such output as streight as possible. The larger the amplitude of such DC pulse the more precise selection of such value is desired. The larger value of such capacitor will have not enough time to get charged and the smaller value of such capacitor will discharge quicker than it should.
For full-wave rectifiers that rectify the voltage bellow 100V the internal power-supply surgery is less-likely neccessary.
For half-wave and tube rectifiers it most-likely does againe due to the large distance between peak pulses.

...and in addition:
Since the rectified RMS voltage is expected to be a-bit lower than same with 60Hz the lack of 220V/50Hz voltage is undesirable.
The best voltage stabilizers, power-conditioners and noise filters at one are TripLite available at digikey.com or newark.com. They're far more cost-effective than PS products.