I hope I can explain this question right, bare with me.

If you set it at whatever setting you like, lets say it is half way up. Now I don't know what the db number is that it may cut, but that doesn't really matter, so for example lets say that half way up will cut 10db. When you are playing, the notes you play will come through because they are more then the 10db it is set at. (Again I am just making up numbers because idk what they are.) Now when your notes are coming through, is the signal open for sounds that are less the 10db.

Say your note is 11 db and your hum is like 8 or 9db, when your 11db note is ringing will you hear the 8 or 9 db hum, or is anything less then what you set it at, not able to come through even if the gate is open from a note ringing that is louder then what it is set at.

Let me know if you guys understand what I am trying to ask
Use 10db as an example: When ever you exceed 10db the gate will open and all sounds will come through, including the hum.

If you're using a guitar with single coils you could probably kill the hum by properly shield the control cavity.
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