Help tracking down hum in onboard dlator

[soje]

I'm in the process of tweaking a Bluesmaster build, and I'm trying to get rid of some humming (no it's not me )

The amp has a built in dumbleator. When I ground the the grid of the recovery stage, the hum disapears. When I ground the other end of the 220k resistor going to that grid, the hum is still there (the junction of the network from the plate, the 220k||500p grid network, and the 270k resistor going to groundt).

I've tried to move the ground of the recovery stage around, but nothing changes :-/

Any ideas?

[Structo]

If you bypass the D'lator is the hum still there?

You may have a ground loop.

I was looking through my layouts and schematics.
I thought for sure I had some stuff on a built in D'lator.
This is all I can find at the moment.
See if this helps at all.