ZPSDX (original, version 1) boosting signal when engaged, slight ticking

[lincolnic]

Hey guys, I need some help with an older build. I'm about to sell my original ZPSDX, but I've discovered a couple of issues.

First, the overall signal level is getting boosted when the pedal's engaged. What's the best way to solve this? Should I increase R3?

Second, there's a faint ticking in the background when the pedal's engaged. I think it's the LFO, as it speeds up/slows down when the Rate knob is adjusted. The ticking disappears if I touch one of the knobs (they're aluminum), so maybe there's some weird grounding issue?

I should add that everything else works properly and sounds good, so hopefully these issues are easily solved. Since the PCB's been out of production for a while, I'm attaching the build doc so you guys can check the schematic.

Here's a gutshot. After I took this picture I added a 10k resistor across the Feedback pot to try and tame it a bit, but otherwise everything's as is:

[lincolnic]

Gonna give this a bump. Any ideas?

[m-Kresol]

for the volume boost, try lowering R5 to maybe 8k2 or something. that should give you less boost.

I don't know how to fix the ticking. maybe try to move your wiring around a bit?

[lincolnic]

I'll take a look at R5, thanks. I'm not sure what I can move in the wiring, though -- you're looking at all of it! The pots and switches are board mounted, and the wires are routed to nearby pads. The brown wire goes right to one of the "IN" pads, the gray wire goes to one of the "OUT" pads. The only wires that actually go under the PCB are for the momentary switch, which shorts the feedback pot. Not sure how that'd pick anything up.

[stecykmi]

hmm, i notice you're using plastic jacks, maybe the case isn't grounded properly? try using a alligator clip to ground the case and see if it goes away.

you could also try a different power supply, maybe the one you're using is letting noise bleed in. using a TL062 for IC5 (the lfo) might help too, i cant make out if that's what you're using.

[lincolnic]

hmm, i notice you're using plastic jacks, maybe the case isn't grounded properly? try using a alligator clip to ground the case and see if it goes away.

you could also try a different power supply, maybe the one you're using is letting noise bleed in. using a TL062 for IC5 (the lfo) might help too, i cant make out if that's what you're using.

I'll try grounding the enclosure. The input/output jacks are both grounded to the DC jack (input jack connects via the 3PDT, output jack connects via the PCB), but it's true that the enclosure itself isn't seeing the connection. Worth a shot!

My power supply is good, it's four regulated and isolated outputs. I bought it from someone on the BYOC forums years ago.

IC5 is a TL062, sorry for the bad photo.

Thanks for the suggestions, guys, I'll try them out on Monday (busy weekend).

[Matt]

The build docs recommend r3 to be 470k. If I'm seeing this correctly yours still has the original value of 1M

[lincolnic]

The build docs recommend r3 to be 470k. If I'm seeing this correctly yours still has the original value of 1M

I do have R3 at 1M, but if you read the doc again it says to change R3 to 470K if you want to reduce the dry volume. I've got the opposite problem! Thus my question in the first post about increasing R3.

[Matt]

The build docs recommend r3 to be 470k. If I'm seeing this correctly yours still has the original value of 1M

I do have R3 at 1M, but if you read the doc again it says to change R3 to 470K if you want to reduce the dry volume. I've got the opposite problem! Thus my question in the first post about increasing R3.

Hey guys, I need some help with an older build. I'm about to sell my original ZPSDX, but I've discovered a couple of issues.

First, the overall signal level is getting boosted when the pedal's engaged. What's the best way to solve this? Should I increase R3?

Just imagine R3 as a gain control on an overdrive pedal. If you want more gain when the pedal is on increase R3. If you want less gain decrease it.

Hope that makes sense. Good luck with it!