Gigrig Humdinger hum issue

lukedlb

I picked up an older white gigrig humdinger from the forum and while testing I noticed considerable hum with only the isolated output used. I did the following tests with the following results and wondered it it behaving as built or these's another unrelated issue.
Powered by gig rig Isolator.
Amps are all 3 pronged grounded.
Humdinger placed at the last position of the pedals.

1. Only Isolated (Main) output plugged in: Hum
2. Both outputs connected to Cinco Cinco but only the isolated output goes to an amp: Hum
3. Both outputs connected to Cinco Cinco and both go to 2 amps: No hum.
4. Humdinger placed inside a switchable loop with only the isolated output following through the loop out to an amp. The buffered output has nothing connected: No hum

I have a passive Arteffects ab-Y signal splitter which does not suffer from any hum problems in any of the above situations (there may be an almost indistinct drop in highs but it could be my imagination after reading the manual).

I'm going to put this to the gigrig team too. I wanted to keep this in my tool bag in case i wanted to do a wet, dry, wet setup where the humdinger would be in a loop. However, it would have been a space saving exercise to have the humdinger in the final position connected to the cinco-cinco, where the choice of one or two amps is made by physically plugging or unplugging the cinco-cinco outputs.

lukedlb

Ok, I may have the answer:
READ THE MANUAL.

The main output is the buffered output, not the isolated output....

Hand to face slap.

lukedlb

As the manual says:

Only use the isolated output when you have already used the Buffered output, or when you have some other single earth to your pedals. The Buffered output will provide your one and only signal ground. 

Sassafras

Glad we were able to help resolve this issue.
You're welcome.