124 is right. when you don't use knobs on amps, instruments...anything, they get really "scratchy". A couple of quick turns will often help.
This is a problem for me, because I only use the volume on a guitar or bass. The rest of the knobs get really "funky".
My kid is my tech, and he's always complaining about this.
We go thru a bunch of tuner cleaner.
R.