I' trying to record guitar using line-in. But there's a noticeable noise in the recordings, and it is present even when guitar is unplugged (only cable is connected).
As you can see its clearly mains hum. But what I think is strange is that the amplitude of the hum kind of depends on how close I am to the cable.
At 2 seconds mark i moved away from the cable, then came back at around 20 sec, at 26.5 I laid my hand on the cable (on isolation, not on the plug), which resulted in that huge amplitude change (amplitude had been adjusted by me to show it more clearly).
Is there any way to fix this so I can record my guitar wihtout noise?