reverb add on mod / hum problem

[firmdragon]

so i'm looking to get some ideas on hum source. i have an older vox ac30 that i'm getting my tech add reverb to. we're using an accutronics reverb pan with simple tube driver stage and recovery stage. in testing it all works. nice reverb no issues.

however as is the case an issue has arisen once we try to finally put it back into the amp. we're getting hum. i've narrowed the hum source down to a particular location , i think. whenever I touch the grid of the tube (where the output from the recovery stage of the reverb connects to the power driver stage and mixes witht the original signal) with a piece of wire the hum appears.

the reverb driver and recovery stage are neatly grouped separately on the board and the grounds are all in one star ground point.

[Amp Kat]

Did you try shielding the run wires. Move them around and see if you can cause the hum to fluctuate. Sometimes you just have to hold your mouth right to find the right location for them.

[Zouto]

Sometimes it helps to turn the reverb pan's output side far away from the amp's power transformer. Using shielded cables for reverb can In/Out is also a good idea.