PedalPCB Median Compressor

M

Mikeydubsj

New member
Hey guys, I am building a few Median Compressors, and I just finished my first one and had a few questions as I can't get it to work.

I've been building pedals for a few years, and have learned a lot, but this is my first compressor. There's a few things in this build that I haven't encountered yet. So I apologize if this i'm just missing something stupid, but here is what I've got.

*Main Issue
TR1 10K Trimmer potentiometer, 3362P type. The PCB itself has a 5 hole spot for this pot, however the only 3362 types of pots i've seen only have 3 poles. Am I wrong in using this? Is there a different pot that I should be using? If anyone has questions that would be amazing.

IC replacements
I've seen other people using the TL072CP chips as opposed to the OP1678. (I had originally bought the OP1678 and the through hole adapter, but the ICs I bought weren't the right size. I will update that in the future. But will this still work with the TL072CP?

Q1 & Q2
When installing, I used a socket for the transistors for easy access to reversing them in case I got it wrong. Is this a bad practice? I just figured it would make things easier in case I made a mistake.

I've been reading up on how to bias the transistors, but i'm not sure i'm even to that point yet since I can't get any audio out of this circuit. Even if I roll the TR1 from one extreme to the other, I get no signal.

Other than that, I linked a picture of my build in here as well. Any help would be greatly appreciated!
 

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Mikeydubsj said:
- Yes, i have sound in bypass (that was my first point of troubleshooting) , I also took a multimeter to every solder point on the pcb (a lengthly process 😂) but everything has connectivity.

- I have tested blend & level controls in all positions with no sound.

- I will test with the blend down and different IC.

I do have new TL072 ICs arriving today, so hopefully that may fix things.
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I am having similar issues with my build, did you solve the problems? If so, what whas the culprit? I'm going nuts trying to figure out what's wrong on my end..
 
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jorisroos said:
I am having similar issues with my build, did you solve the problems? If so, what whas the culprit? I'm going nuts trying to figure out what's wrong on my end..
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Dude... no. It's been frustrating. I replace the IC with the proper ones with soic adapters, and it still wasn't working. I built my second one lsat night thinking maybe I had messed something up with the first PCB or ruined any of the components while trying to replace all my ICs . I double and triple checked all my solder joints, and I still have nothing. I'm beginning to wonder if my Transistors are the issue. I have built about 15-20 pedals now, and I've never had an issue like this. I'm at a loss as to how to fix it.
 
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From the image in the build doc Q1 and Q2 should be installed with the flat sides facing down toward the footswitch.

They're wrong in the picture, but you said you tried them both ways. Are they in correctly now?

1760472143042.png
 
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jorisroos said:
I have sound when bypassed. When engaged I get ether a lot of hiss noise or when adjusting the trimpod no noise at all. Tone, compression, blend and level seem to affect the hiss, so I am at a loss
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This may (emphasising ‘may’) have to do with your selected JFETs. My first Median build (details here) failed because the JFETs wouldn’t bias correctly. The next one I built using SMD 5457s worked fine.

That said, check your soldering to eliminate any possible cold joints, shorts, what have you. 99/100 problems I’ve experienced have been of my own making. Try gently tapping components one by one with a pencil to see if there’s a loose connection somewhere, for starters.
 
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