I think any transformer MAY effect the sound. I was using a Furman AR-16 voltage regulator (which uses a variable torroidal transformer to regulate voltage) on my Cambridge Audio 840c and I noticed a considerable amount of high end "fuzz" and other distortion in one channel. Went away completely when I removed the Furman.
Best bet is to see if you can alter the voltages via taps on the transformer within the unit (as has been suggested).
Best bet is to see if you can alter the voltages via taps on the transformer within the unit (as has been suggested).