Improved Hum-free A/B/Y is .... humming?

[morcey2]

I built a hum-free a/b/y from geofex and it works great except for one thing.  I get lots of hum from it.  Actually the hum I think is coming from the guitar because it's floating and doesn't have a real ground reference.  That or I'm just smoking something.  Here's pictures.



I found that if I run a jumper from the ground on the input jack to the ground on one of the output jacks, the hum goes away.  Should I just add ground-lift switches to the output jacks?  I'm using a strat which will hum anyway, but this is far and away worse than what it picks up plugged into the amp directly. 

BTW, the enclosure is temporary and so is some of the wiring.  When I get a smaller enclosure, the wiring will be shortened as needed.  Please ignore the poor shielding job.  But it works!

EDIT:The bottom of the board is insulated from the shielding.  It doesn't look like it though.

Thanks,
Matt.

[MetalGod]

I seem to remember that one of the outputs should be isolated from the chassis - have you done this?

[morcey2]

Both outputs are isolated.  The only connection to the chassis/shielding is at the input jack.  I'm pretty sure it's not a ground loop problem, but a gotta-ground-the-guitar-somewhere problem.  Maybe I should just isolate one output and ground the other.  There still wouldn't be any ground loops and the guitar will have a ground.  That would probably be the easiest.

Matt.

[theundeadelvis]

When I built mine I had hum with some setups and not with others. What I did was add a three position switch that allowed me to have the outputs isolated, one grounded, or both  grounded. One of those options would give me a hum free setup. Not sure if it makes sense, but it seemed to work for me.