@Vmax
@dchang05
If you haven’t yet, you guys might be interested in considering a Schumann resonator.
Why it can work, it might have to do with the effect on the listener and the equipment both.
All electronics ever have been designed and constructed under the influence of the Earth’s field (and we’re all born under it too) so it’s natural that stabilizing its average frequency in the room can affect the performance of electronics and our nervous system too.
(This is why a 100% mu-metal coverage would not be a good idea in any case)