11-29-2019, 08:47 AM
There are rc filters on input output lines to speakers. (P14 of Pinebook pro schematic). I’m not as sure about headphone jack but if I’m reading it right filter components have different values for head phone . Given this you might not have a whine via headphone. A change to the filter compost values might be a fix at the cost of a narrower frequency range. The cheap home brew solution might be to wrap the speaker leads around a ferrite donut to act as inductor and perhaps more of a low pass filter. This will probably not work for a very high pitched noise but if it is the pulse width modulator for brightness is should be low enough to work. Waiting on my pbp so I can’t try unfortunately.