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Where did you get the enclosure from? It's great as well. And yes, having a separate patch box will help with HF interference.

I am using eagle for schematics :-)

P.S. This is an impressive work, if you get all of this to work. Having designed Eoo3, I know about the effort. Having a display and other digital components in such a unit can induce some serious HF noise in the audio path, and fixing that is a PITA. I had issues with the 7-segment display driver... my goodness!

If I should ever design a 3rd version of this, I would try to add a WIFI Chip (ESP-wroom) and make the unit configurable via smart phone. Other features I failed with were configurable fx order and configurable displays/label on the fx buttons.

For the digital potentiometer: It does not work for continous volume control, it's just not discrete enough. It's ok for setting a static volume, though. You will have to mute the output for the volume change time, though, because it creates some nasty artefacts during the change... They are available in 50k and 100k (recommended)as well.

Summarizing some points for your debugging endeavor concerning the pop:

I see no reason in the hand drawn schematic of the mixer above for a DC on the output. For the spillover circuit used in Eoo3 I provide a simplified view of the relevant part of loop 7:


It's hard to image, where the DC on the output should come from in bypass mode (that's the mode the schematic shows): C27 should block all DC coming from the circuit, if R52 is connected to GND, there is no chance for a potential difference on the OUT.

In FX mode, Return is directly connected to the OUT Jack, so if the FX itself has DC in it's ouput, that would be the source (unlikely, but easy to measure). The IN signal is fed to the FX in AS WELL as towards C28. It is directly fed to the Output via C30, where it is mixed with the return signal (this is where phase issues might occur with the direct signal part of the fx return, but I did not care, as I never had any issues).

On the input, the send is grounded in bypass mode. Switching to FX mode should not create any popping. The output switch has pulldowns on both sides, this should not create any popping either.

If I fully understand my approach (it's been a good year now...), the direct signal in fx mode coming through C30 should not cause any issues. I think I tested that as well, but to be 100% sure, you could test the following:

Pull R60 (any trails would disappear)
Switch from bypass to FX mode
If the pop is gone the phase inverted (IC1A!) direct signal does not go well with the non-inverted signal from the return path (RET7)

Can you try that?

Nice. I am very much interested in the technical details. Schematic, Display, code :-)

I'll be back home next week so I'll chime in too. The tails board is ready to go in and I think that'll be a big part of my rig...getting in and out of delays.

Cool. Gordo, maybe you can check, if there is DC on the output in spillover mode. If that is the case, please let me know. I would fix it with a new design for just that board.

Marshall Arts, I visited, examined and tested everything you suggested in that link, but things didn't work out well... On the other hand, your looper schematic works perfectly in terms of tone and volume and function, it's really amazing! BUT I still get that huge pop when spillover is turned on or off via relay, it's not that innocent bypass pop, it's something else... Measuring voltage at the output Jack I get 0V when bypassed, 0V when fx is on, but 1.1V (!!) When spillover is activated (constantly). It's that big voltage difference that makes the huge pop... Any ideas on that?

Is that 1.1 V DC? Hard to imagine, as the only connection to the output is a cap (e. G c27 for loop 7) and a resistor to Gnd (r52) for bypass in spillover mode. For fx on in spillover mode it's just the return signal and a resistor to Gnd (r40) and another cap (c30). Did you try other caps as well? There should not be any DC in that part of the circuit.

I will check with my Looper, but it will take some weeks... I don't use the spillover loop and don't want to rip my board apart right now.

Maybe I find time for breadboarding, who knows.

Please post the schematic you are using, and where you measure what. Or at least pictures of your breadboard.

I decided to skip phase reversal... Never needed it...

P. S. The E003 uses jumper switches to change loop 7 and 8 to true bypass loops. The return signal is buffered by the effects in the loop. I Breadboarded a lot, and this solution was the best I found.

Different approaches have been discussed in this thread

https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2Fwww%2Emadbeanpedals%2Ecom%2Fforum%2Findex%2Ephp%3Ftopic%3D28875%2E0&share_tid=28875&share_fid=53198&share_type=t&link_source=app

I only have blend circuits in the spillover loops, and it's actually not too much popping. Can you point us to the sources you found? And maybe a schematic of that part of the circuit? And yes, maybe a separate thread in this forum to discuss your circuit and how to fix it...

Hello everyone, it's my first time here and boy oh boy what a wonderful forum this is! I might need to start a new thread for my own programmable looper build which is coming very soon... But I have a couple of questions that the experienced looper builders might be able to help with 

I have separated stomp unit and relay unit (to add new stuff whenever needed and be more versatile away from the pedalboard
So the stomp unit has a touch screen to be programmed easily. The relay unit features 10 loops, midi out, 4 amp switches, switchable buffers for input and output (adjustable gain too) and I am currently working on the trails mixer for loops 9 & 10. But FOR THE LOVE OF GOD, how do I get rid of the true bypass relay pops? I've been reading about true bypass for days, and it seems to come down to either accepting the pop, or muting the output for 10-20ms until the switching is complete.... So what are your thoughts? Which circuit do you use for that job, and whych parts do you mute, output only?

Thanks for your patience...
Vangelis

See schematics for the E003. I use a solid state relay to mute just the output for 10 ms. However, another problem is a couple of leds changing, which might feed back into the power or Gnd rail. This is nasty, esp. With delays in the spillover loops. Read r. G keen for some approaches on how to fade in leds slowly to prevent popping.

I think there is still room for a battery :-)

Cool. I guess that hookup wire is totally fine, unless you use multiple high gain pedals. Let me know, please. Hope, that the spillover works for you and does not create switching noises... So excited to see yours come alive!

As a motivation: Re-labelled mine and use it mainly as a controller for my HX Stomp and Amp Channel Switching. Looks like this these days: