For a few years now I’ve been using video bending as a way to learn more electronics. It wasn’t too long ago I thought a fun project would be to really experiment with audio reactivity on a “Mutant Enhancer”. I got some BJTs and built one of those dirty “Enhancer” circuits on a breadboard and got to twiddlin’ and turnin’ knobs.
First I built a dirty 2 band envelope follower to feed the BJTs, then I bent that Enhancer all up looking for some cool effects and was really happy with what I had.
With all the connections between the envelope follower and the bent archer board I was really struggling with getting a semi-permanent prototype (I could bring to shows). So I decided now was a good time to learn PCB manufacturing. (Jesus christ was that bad timing with the tariffs on China.)
After trouble shooting my way through a poorly designed PCB, hand soldering 603 surface mount parts out of cheapness and blowing up an SMD Op-Amp because I installed it upside down. I got my second prototype up and running and to my surprise. All my bends are having the exact same problems as the previous iteration. Sick!
They are all behaving completely differently than the breadboard prototype!
I checked my old breadboard prototype many times over and my schematic matches perfectly. Surely I can’t be that wrong so consistently?!
So I guess my question is, would there really be that much of a difference between the bread board and the PCB? Are the electromagnetic forces acting between the rails of the breadboard playing that much of a roll?
The only thing that works as it did is the “Blur”. Just a capacitor to ground on the input.
I also noticed the PCB enhancer is a lot more… enhancey… The sharpness and brightness come up a lot at the loss of a little contrast. Also some weird looking warping that kind of reminds me of video aliasing. I was at least smart enough to throw in a bypass switch.
CrazyViz_01.pdf (297.7 KB)
Can you describe the issues a bit more?
as in: what did you expect each function to do, and what is the change between the breadboard version and pcb version.
what I do see, is that your power section lacks decoupling capacitors. This can cause instability and interference.
Use a 100nF at each opamp (as you use a single supply). place these close to each opamp on the pcb layout.
It can also be a good idea to use ferrite beads to filter high frequencies coming from the PSU.
What trace size did you use? It looks thin.
Hey thanks for replying! I’ll have more details to come. I definitely posted this out of frustration before doing my due diligence. I discovered after reviewing the breadboard version that I used different NPN transistors. I can’t imagine that doesn’t play a role somehow. I fear this misjudgement will impact my performance review.
I’ll see about high frequencies from the PSU, though that’s pretty low on my priority list. I didn’t include a decoupling capacitor on the op amp power supplies because honestly I’m not worried about a noisy audio signal. It’s going to an envelope follower anyway. Although as I think it through it may be what’s causing the high band indicating light to light up a little bit with no audio signal. So I’ll throw that on the list too.
Traces are 0.4mm and power is one phat mm wide. That’s pretty big from what I’ve gathered.
I’ll update.
So there were several large mistakes.
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The breadboard enhancer was built wrong! I had accidentally put R6 and C1 to ground instead of +12V. This also rendered the “gain” pot and C4 useless Isn’t that nutty? I tell ya, if you love being confused get into electronics. The cool thing is that this allowed for a very different set of effects.So I’ll be continuing with those
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Low band audio filter was routed wrong making it do bad things instead of the the good things we wanted.
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The video signal was actually routed to go straight to ground, with the ground routed to pass through where the signal should go. I don’t know how I saw any video at all and hey maybe there’s something fun to discover with that.
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The audio port is too small. 
Thank you for your help! Now I must re-design yet again!
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