I built myself a Touch replacement about 3 years ago, based on a Raspberry Pi 3 Model B, a HifiBerry Digi+, and the official 7" touchscreen. This feeds into my Beresford DAC via optical link.

It has been fine for most of that time but recently I have been noticing a lot of noise. I would describe it as a slightly scratchy static-y sort of sound. It is not extremely loud but I am using headphones and it is is loud enough to be noticeable and annoying. It can be heard intermittently when no music is playing but it also happens consistently and very audibly just before/as a track starts.

I have a Chromecast and a CD player connected to the same DAC and I don't hear any noise from them. I took my old Touch out of retirement and put it in place of my self-built version (on the same DAC input) and this sounded absolutely fine.

Does anyone have any idea what might be responsible for this sort of noise and if there is anything I can try to correct it?

Thanks.