overdrive troubleshooting help

[bob, just bob]

I made an overdrive for a friend that basically strung 3 fetzer valves together.  I liked how it sounded and was interested in a dual overdrive, so I tried putting two together.  I have the first 3 gain stages on a switch such that they are only active when the second 3 are active.  It worked on the breadboard, but when I soldered it up and stuck it in a box and it doesn't.  Here's what I've tried:

1) looking for cold solder joints
2) making sure the components are connected where they should be
3) checking that connections that shouldn't exist don't
4) I biased the jfets' drains to about +4.5 volts; the gates are all at 0v; the sources are all between +0.2v and +0.6v

When all 6 stages are on, there is noise coming through that I can reduce by turning down any of the gain or volume controls.  When just 3 stages are on, I don't hear this, but it isn't really a noisy circuit to begin with. 

I removed the circuit from the box and tried it.  In general, I may have some static until I touch the guitar strings.  But, in this case, the opposite was true - touching something that was grounded caused hum.

Any suggestions of what to try next?  Thanks.

[grolschie]

Perhaps check for solder bridges where they shouldn't be? Sometimes they are hard to see. I have never used one, but people sometimes suggest using an audio probe to debug.