Daniel Prieto posted an answer for this Alesis M1 Active 320 USB Speakers:
"I have the same problem. ¿What happened when the problem started? I disconnected them and..."
Daniel Prieto posted an answer for this Roland Cube 40XL Guitar Combo Amplifier (40 Watts, 1x10 in.):
"Sadly, that doesn't seem to be the schematic for that amp."