Anyone else’s OP-1 produce a strange extra sound during grooving when the unit is charging?
yep. it’s magically gone with with a noise isolator.
yes. Basically a ground loop except it’s a high frequency whining noise rather than the common hum. The noise isolator works and is cheap. DI units should also do it. I just turn off charging when I use my OP1, leave it plugged in when I don’t.