You guys may remember that I have changed the layout of the pots on this pedal, forcing me to run wires to the pots and tone cut switch rather than PCB mounting. I have completely rewired the pedal from my first posting when I was having issues with picking up a radio station and had a high pitched squeal when cranking the volume and treble pots all the way up. After rewiring, the wires from the input/output jacks to the PCB are approximately 3" in length, as are the wires from the foot switch to the PCB. Each must cross under the PCB to the other end due to clearance issues that forced me to rotate the PCB 180 degrees. I have significantly reducing the amount of wire that was used from my first attempt, however, there is still a lot of wire compared to the stock pedal layout.
The radio interference I was getting is all but gone and the squeal as well. I now seem to have an issue with background noise. It seems more pronounced than the first time I wired this pedal. If I turn the volume, bass, and treble all the way up, I get a fairly significant amount of background hiss through the amp, especially if I plug into a single coil guitar. I get a much lower level of hiss with my Humbucker guitar but it's still there. The hiss does not occur when the pedal is in bypass.
What's interesting is that the first time I built this pedal, it didn't work when engaged. No sound. I eventually resolved that by reflowing the switch wires. The same thing happened the second time. I think I do a decent job of soldering so I'm not sure what that's all about.
Obviously this is an amplifier pedal so maybe some level of hiss when cranked up is normal. Can anyone who has built one of these tell me if they get any hiss? I can just start hearing it even if the volume and treble are only half way up.
- The PCB is free-floating in the case but I'm assuming is sufficiently grounded through the input/output jacks, but when I hear hiss, I think grounding issue or shielding issue, but I'm no expert.
- I have a sheet of adhesive copper shielding foil as is used to shield inside guitars. I have yet to shield the backs of the pots but will do so. I don't think this will make a difference in the hiss as it occurs even when I remove the assembly from the case and can place each component well apart from each other.
- Obviously the length of the input and output jack wires doesn't help the situation. I currently have the conductors braided. I'm not sure if that makes a difference one way or another. I was simply trying to keep it neat and tidy. I could try using the copper shielding tape to wrap them if you guys think it might help. I could also find some multi-conductor shielded cable and replace them.
- The wires to the foot switch are also an issue. If I lightly pinch those with my fingers, I can get a bit of hum out of them. Would shielding possibly help that situation?
- Is there any point in shielding the interior of the pedal with copper, the same way you might shield the cavity of a guitar (since I happen to have a sheet of guitar shielding copper)? It may not solve the hiss but might prevent picking up anymore radio stations.
Worst case I could try and flip the PCB back around into the correct orientation but I'd have to replace at least one of the tall caps and lay it down flat on the board to create clearance.
Any suggestions are welcome. I'd especially like to know just how much hiss, if any, is inherent with this pedal. I don't want to do a third rework if this is normal or if the hissing problem likely has nothing to do with long wires from the jacks or foot switch. What's the most likely cause of volume related hiss in a pedal like this?
OLD Wiring - this is now GONE. What a mess.
NEW Wiring - note the greatly reduced amount but still not ideal. Orange wire is to a secondary LED indicator for the tone cut switch.
Component Layout (pots have since been replaced with Lug type equivalents rather than the kit-provided PCB mounts):