Serge Auckland wrote:

A mains filter will cost a few pounds/euros. You're not thinking of an
audiophile one are you? That's a £€5 part in a £€ 50 box with a £€ 1000
price tag.

I can only find the audiophile ones. Would you kindly show me where I
can get one a lot cheaper than that?

I get drop-out from the DAC when flicking the mains switch on my Cyrus
tuner, and it's plugged into a different gang plug from the DAC!