I have an annoying little noise that is constantly emanating from my speakers. At first upon Googling I thought it was the usual hum, hiss, or whatever sounds that is the by-product of a normal audio configuration. Although the sound persists even with no inputs connected to my amp (my configuration is just 4 speakers connected to one amp, nothing else), and all of the speakers connected are unpowered, so I don't know if that eliminates the possibility of a ground loop? Also, interestingly the amp only has a two-prong plug and therefore does not have a ground.
However, while trying to figure out whether this was hiss or hum I measured the frequency (admittedly, using an old iPhone app, but the app is pretty darn sure the frequency stable at 240 Hz).
Upon Googling this it seems that possibly, this is indicative of an issue with the power supply (or something related to power) because 240 is a multiple of 60, and that is the frequency of the power here.
The sound is definitely coming out of the speakers, not the amp. And as I turn up the treble/bass the noise increases, and vice versa.
That's all I've got, if anyone can help me confirm what the problem is (and whether it is repairable or if I should buy a new amp) it would be much appreciated.