Did you notice that all inputs from the selector goes through tape monitor switch? Give it a dozen of pushes and it might improve that noise issue. A dirty contact could be the cause of that. I soldered a bypass on the switch as I don’t use tapes anymore.
Yes all the inputs goes through tape monitor switch, but there is one input (marked as “tape” I think) doesnt go through the selector, I simply used that input so it bypasses selector
