Hi Larry. Yes, it could be your step up transformer. When using a transformer, you need to over spec the transformer otherwise it will effect the sound in ways you mention. While this may be totally overkill, I wouldn't consider using one unless its capacity is 9 to 10 times that required by the amplifier. When over spec like that, they do not restrict the amp and serve to reduce the noise on the power lines.
You could could try a larger capacity xformer and see if it sound better or you could contact the vendor and see if the amplifier power transformer could be wired to 110v. I suggest you do the latter. Many amplifier transformers have multiple wiring options to accept 100, 115 and 220 volts.
Regards
Paul
You could could try a larger capacity xformer and see if it sound better or you could contact the vendor and see if the amplifier power transformer could be wired to 110v. I suggest you do the latter. Many amplifier transformers have multiple wiring options to accept 100, 115 and 220 volts.
Regards
Paul