[Analogue man]

I found that Powerline units commonly send out interference that is picked up by some amplifiers at a very low level and some pre-amplifers at a significantly higher level, a magnetic phono pre-amp (obviously with the most gain) being the worst. I tried some medical mains filters that reduced the interference but did not kill it completely, I chose the easier route at home and installed a cabled data network instead which is fine.