TL;DR: The pedal is not working correctly. I suspect it is a wiring error on my part and I am looking for it.
Full Story: I went to test the new pcb for the SSM2166 compressor pedal. The laptop on my test bench had not been used in several months, and Windows had updated. It now was forcing me to log into a Microsoft account and use OneDrive. I don’t need OneDrive and I don’t need a Microsoft account for this computer that is only used for testing and audio recording. Not only that, I did not remember the password for that laptop’s account. But, I had written it down, and after a lengthy search, I found the password and got in.
Next came a succession of errors on my part related to cables and jacks that were not labeled. Once I got that sorted, and all the cables plugged in correctly, I could run a few tests. The pedal did not work correctly. It worked in bypass but not when compressing. That sounds like a wiring error but this is a buffered bypass pedal so I would not expect it to work if the bypass wiring was wrong. But it did.
I looked closely at the switch wiring. It was correct. I suspected the battery but it was lighting the LED to full brightness. I tested 2 other pedals that were on the bench and they worked as expected (on the same battery).
Back to looking more closely at the inside of the comp pedal. Then it struck me… the 3pdt switch was oriented correctly for true bypass, but turned 90 degrees for a buffered bypass. Doh!
I pulled all the wires off the switch and turned it around. All of the switch lugs were plugged with solder so the wires would not go back in without a fight. Blah, blah, blah… I finally got it wired up.
So after some tests, it passes a signal on bypass but not a good one. It is losing some volume. At this point, I have to take a break. It is hot in that room and I am sweating, and I have looked at the wiring too long. Later, after resting my eyes, I’ll have another look at it. I may have damaged the op amp when moving cables and wires.
4/27 Update: I was right in that fresh eyes would be able to spot the problem. It only took me about 2 minutes to find the misplaced wire in the prototype’s ratsnest. The good news is that voltages are perfect and the buffered bypass is clean and stable. The bad news is that it does not compress properly. I was afraid of that because I went WAY off the datasheet’s basic design on this version and it looks like that was a bad idea because the internals of the chip were not doing what I thought they did. I still have to test the ssm2166 chip to make sure it is functioning properly but I expect it to be okay.
