AB bypass looper pop

[kr2p]

I'm having a little trouble with an AB bypass looper popping when I switch between the two loops - a clean one which has a load of pedals, and a dirty one with just a Rat that's always on. The pop is most noticeable when I have a delay on in the clean circuit as you get all of the repetitions which is quite annoying.

It's a completely passive AB looper and I've tried a bunch of things. Originally it was just a plain true bypass switcher which linked the unused send to ground and left the unused output floating. This popped. I tried the most basic thing of putting 1M pull down resistors on all sends and returns. Still popped. I then added .1uF capacitors at each send and return along with the pull down resistors, the idea being to treat the effects in the loop as one big active circuitry requiring its own input and output caps. This still popped. I also tried 1k current limiting resistors before the capacitors at the sends and after the capacitors at the returns. This still popped. For clarity the latest setup looked like the final figure in this link

https://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

with the "circuit block" in the diagram essentially being all of the pedals in the loop.

The pedal has an LED but the ground is separate to the audio ground, so as far as the audio path is concerned there's no LED or power going to the pedal so this isn't the problem. And to verify this it also pops when I don't plug in the power.

I've tried going straight in with my guitar into the input, as well as going through a buffer and it makes no difference. I've tried moving it next to and away from a power supply to see if it is some sort of induced noise but there's absolutely no difference so this isn't it either.

I feel like I've run out of ideas here so if anyone has thoughts that would be amazing. I should mention that I have a boss LS2 which doesn't pop as it's an active buffered circuit, but I'm trying to avoid using it as it adds a bit of hiss which seems unnecessary since a passive pedal should be able to do the same thing.

[idy]

Have you tested to see if any of your pedals is leaking DC on the input or output? Really the question would be if the string of pedals in the "clean" side is doing it.

You may not need all that, the caps and such. I would be suspicious of the stomp switches, the cheapies don't always perform noiselessly. It's a simple pedal, I would try to build another (if this works, you'll want two anyway) and maybe spring for a "better" stomp switch.

[kr2p]

Have you tested to see if any of your pedals is leaking DC on the input or output? Really the question would be if the string of pedals in the "clean" side is doing it.

No I haven't tested the pedals in the chain for DC leakage, how would I go about doing this? Is it simply a case of measuring across the tip and sleeve of the output/input patch cable using a multimeter?

You may not need all that, the caps and such. I would be suspicious of the stomp switches, the cheapies don't always perform noiselessly. It's a simple pedal, I would try to build another (if this works, you'll want two anyway) and maybe spring for a "better" stomp switch.

I've been thinking the route of caps/resistors might not work as I would have thought something would have made a difference. I can have a look at getting a different switch, although the pedal was actually one I bought from bright onion pedals who do really great high quality hand wired stuff that I tried modding a bit with the resistors and so on. It feels like a really solid 4pdt switch and the wire and jack sockets are all high quality so I don't think it's a cheapie.

[idy]

You check for DC like you said: with pedal powered up and engaged you use your meter on DC volts on a cable plugged in. You'll probably see at least a little...

4PDT are in my limited experience noisy, worse than 3pdt, just more work for the plunger, more to go wrong. But they allow you to do am LED. I have made A/B loopers for testing pedals and for the kind of set up you are using, but 3pdt no LED.

[kr2p]

Just measured and there was pretty much no DC. At the start of the chain there was about 1mV and at the end it measured 0. It measured more potential just moving the leads through the air so that's probably not it.

It's probably the footswitch as you say. The pop isn't that loud, and I only really notice it when there's the delay on and it does the clattering noise, so I will probably just live with it. Once we're able to practice as a band again at high volumes I'll see how much it bothers me but I think for now the reduction in hiss, which comes right before my gain pedals, is worth it over the silent switching of the LS2.

[duck_arse]

have you measured for DC leakage at the input jacks of your amplifier?

[kr2p]

Yes it's about 40mV or so across the input when there's no pedals plugged in, although would this matter as there are other pedals after the switcher?

[idy]

A looper is so simple and useful, If I were you (IIWY) I would just build another: 6 jacks, an enclosure, a 3pdt, some wire.  No LED. Maybe splurge on a 3pdt like the $17 FullTone bakelite baby. Really even the blue Chinese ones should be good enough.

I use them to test circuits that are not boxed up, and the way you are doing it. Also make great stocking stuffers...