Hum from FX Loop until an Effect is selected

[EvileOL]

Wondering if anyone can help me out. I have a delay then an EQ in the FX loop of the amp using the GCX.

The FX loop is humming, until I turn the delay on, then it's crystal clear and quiet.

setup:

guitar>
1. Tuner
2. Powerscreamer
3. Compressor
>amp

FX Send>
4. Delay
5. EQ
> FX Return

[JohnClark]

Try connecting the FX Send to the In of GCX Loop 4, then run the Out of GCX Loop 4 directly to the FX Return. With nothing else connected to GCX Loop 4, and with GCX Loop 4 bypassed do you get the same problem?

Try the same simplified test on GCX Loop 5... do you get the same problem there?