i know, i know, expensible mains cables etc are all a big con

but

i just bought a new setup – wharfedale lintons and leak stereo 130 amp. i was enjoying the sound but i started noticing a strange hum, fading in and out, easily audible at least 5m away.

turns out it was coming from the transformer of the amp itself. that is, audible even with no speakers attached.

i tried reproducing in the morning – nothing (unless pressing my ear up to it). but the next evening it came back.

i have a battery backed ups/apc thing. so i added that. yes i am a nerd.

powering the amp via ups via mains (ie just surge protection) the issue is still present.

switching off at mains and unplugging has same effect (and i am in the uk, there is an earth pin) – the hum stops phasing in and out and changes to an entirely consistent, quite quiet, and more buzzy hum (and the ups beeps obviously, which is annoying).

SO

should i buy some snake oil product, assume my amp is faulty and replace it like-for-like, get a different amp, stick it in a cupboard, learn to love it, or something else?

plan a is to at least hold my ear up to replacement one in the shop, and if it is audibly different up close then go from there, but i am thinking this might be inherent to the product…