While I am a firm believer that the listener is a major variable, and that often differences will be perceived when nothing whatsoever has changed (including the recording), I think that if the differences here are as great as you seem to be describing, something else is going on.
I'd suggest first that you buy or borrow a multimeter, and measure your line voltage on the good days and on the bad days. Also, take an AM portable radio, tune it to an unused frequency near the bottom of the band (e.g., 540kHz), set the volume level to a repeatable point, and compare how much rfi it picks up when placed near your power cords, on the good days and the bad days.
That will address (at least roughly) two of the four ways I can think of by which power might be affecting your system (voltage and noise). The other ways would be harmonic or other distortion, and dc offset, but you would need more specialized equipment to address those factors.
Beyond that, my bet would be (as Mapman suggested) that you have an intermittent problem in one of your components. Perhaps a capacitor that is leaky and on the verge of breaking down. Perhaps you can borrow some other component(s) to swap in on the bad days.
Regards,
-- Al
I'd suggest first that you buy or borrow a multimeter, and measure your line voltage on the good days and on the bad days. Also, take an AM portable radio, tune it to an unused frequency near the bottom of the band (e.g., 540kHz), set the volume level to a repeatable point, and compare how much rfi it picks up when placed near your power cords, on the good days and the bad days.
That will address (at least roughly) two of the four ways I can think of by which power might be affecting your system (voltage and noise). The other ways would be harmonic or other distortion, and dc offset, but you would need more specialized equipment to address those factors.
Beyond that, my bet would be (as Mapman suggested) that you have an intermittent problem in one of your components. Perhaps a capacitor that is leaky and on the verge of breaking down. Perhaps you can borrow some other component(s) to swap in on the bad days.
Regards,
-- Al