Ground hum issue - May not be Kemper related

  • I have a battery powered pedal (DOD 440 Envelope filter) plugged into my Kemper rack's FX loop. The loop is situated in Stomp B. The pedal works fine when the stomp is engaged, and as long as the pedal sits on top of my rack case, I get no noise. However, I recently mounted a sliding rack shelf into my case and when the pedal sits on the shelf I instantly get a lot of (what sounds like) ground hum. I tried messing with the Kemper's ground lift switches, and also changed the patch cables, but this didn't help. When I put something non-metallic between the pedal base and the shelf the noise goes away. My Boss DS-2 doesn't produce the same noise (but it has a rubber base).


    Can anyone suggest why this is happening and how I can fix it at source without using a workaround such as removing the shelf, leaving the pedal on top of the rack, or sticking something permanently on the pedal base?