Voodoo Lab

I'm having trouble getting #3 & #4 to work. I reset it so you have to turn on/off each pedal because I use different combos of amps. #1 and #2 work fine. But 3 &4 have almost no volume. If I switch cables around, then AMPs 3 and 4 work fine plugged into 1 & 2, but then AMPs 1 and 2 (now plugged into...