Tonepad Chorus - Low freq hum w/ Max Effect Level

[Stratomaster]

Hello, I was redoing my pedalboard and noticed that I get a low frequency hum that's quite noticeable (sounds like bad ground) when I crank the effect level pot.  I added the effect level mod per tonepad instructions.

I can dial out the hum by just turning down the pot, but I also turn down the effect that way.  Any ideas on what could be the source of the hum?  I've used a few different power supplies (including a t-rex chameleon) and still have this problem--so I believe it's the effect, not the power, that is suspect.

The hum isn't overbearing and I can hear that the effect is working correctly--aside from the audible hum. 

Troubleshooting measures I've already taken were to change out the caps in the power supply section and replace the zener. Neither accomplished anything. 

Any help would be greatly appreciated.

[amptramp]

If you could temporarily operate from a battery, this would permit you to see if it was hum conducted via the power supply or picked up from the ambient 60 Hz field.  In some cases, running a connection to ground may reduce the hum.  I found that recently on a pedal that had a severe hum which dropped about 20 db when I connected the ground to the zero volt rail.  (I am using an Ault wall wart adaptor with +12, 0, -12, GND and spare connections.  Wiring GND to 0 provided this reduction.)

[Stratomaster]

Thanks for the suggestion.

There is no hum when run off the battery, only with the power supply.  This is very strange.  Also the Visual d Sound 1 spot seems to power the pedals without hum. Looks like this is just some weird interaction between the T Rex Chameleon and the chorus I built.  I'm very disappointed in that supply seeing as how they power supply had everything needed to satisfy the footage requirements of my pedal board.

What is even more strange is how not all pedals are acting up.  Tried different outputs to no avail. Used a daisy chain and tried powering directly as well (using both the T Rex and the 1 spot) and only got hum with the T Rex when using the chorus.

Thanks for your help and unless you or anyone else has possible solutions then I'm going to contact T Rex or look into getting a refund.