I have an Allocacoc Power Cube - basically an extension socket with 2 USB ports included - that makes a very annoying intermittent high-pitched sound while charging most devices. The sound is clearly correlated to the power draw and well within hearing range, I'd estimate about 13kHz or so. I think it always used to be there, but it seems to have become much more noticeable lately.
I imagine the DC conversion circuitry in the socket isn't great, but still it's very convenient and I'd like to fix it if possible instead of buying a dedicated charger. Does anybody know if this is possible? Could it be something like a damaged capacitor, or is it a fundamental design flaw?