Question on extra hum in “fat” and “treble” switch

[sthebluesman]

I noticed that when the mini-toggle is in the center position, the amp is very quiet but in any other position, there is extra hum. It sounds like a grounding issue. The center terminal on the switch is wired to the ground terminal (upper) of the input jack as it should be according to the book. Is this normal? Has anyone tried to run an extra ground to the switch to see if they can tame the hum a little?

[djroge1]

I don’t recall having any extra hum when engaging the switch.

[sthebluesman]

Maybe it will quiet down when I get it in the cabinet. Right now, the chassis and speakers are sitting on my table. I won’t have the cabinet until next week. I tried running a jumper wire from the center terminal to the ground lug and that had no effect on the extra hum. The amp sounds good in those boosted positions but with the extra noise levels as compared to the center position which is dead quiet.

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