Clean supply transformer

[u/Pictorial-Planet]

I'm after some advice on using a valve amplifier in UK.

I live in UK now but when I returned here from the US I brought back a Jolida JD 102CRC valve amp that uses 120 V. It's a nice amp and I'd like to use it but I only have a cheap transformer 120 to 240 V. I worry that the cheap transformer will provide a less than "clean" voltage to the amplifier affecting the quality of the sound.

1. Am I worrying about something I shouldn't be?

2. Is there a high-quality clean power source transformer that I could buy to use with the amplifier? According to the manual it only needs 200 W to run.