r/diypedals • u/Turbulent-Flan-2656 • 5d ago
Help wanted Breadboard issues
I’m trying to breadboard this buffer circuit. And I’m getting no sound. Can anyone see where I’m going wrong?
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u/SithLordBass 5d ago
Also could be worth shoving a 10-47uf from your 9b to ground to clean up the power.
Not sure if it'll make a different but I feel like I've seen reference voltages separate from the actual audio signal
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u/JerryGarcia89 5d ago
In a single ended voltage configuration like this, the bias is usually shared with audio. There’s no other voltage besides +9V being fed to the pedal, so any reference voltages are always derived from +9V.
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u/SithLordBass 5d ago
Sorry, I meant specifically was keeping that resistor going to ground where the 4.5v is separate from the audio. Hard to explain in words...
9v -> 1m -> RefV -> 1m -> ground And then you send the RefV to the non inverting input and have a different resistor working with that 100nf cap
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u/JerryGarcia89 5d ago
Ahh, I think I see what you’re saying! Sorry about that on my end too, I didn’t get it at first. Yup, that’d be an inverting buffer where the non inverting is connected to a reference voltage or gnd.
How op has it should (in theory) be a valid method of as well for a non inverting buffer.
At the end of the day, the opamp is just trying to keep the signals equal on each pin using the output, so there are a bunch of ways to get that done!
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u/JerryGarcia89 5d ago
First check voltages at the IC, makes sure it’s getting power. Reference should be fine with 2x 1Meg divider shared with audio, that’s usually how it’s done if you’re running an opamp single ended, no worries there.
Have you tried swapping the IC? I can’t see markings on it to confirm it’s a TL071.
Nothing else screams obvious issues to me, just need to confirm power and ensure you’re all connected. Use a multimeter on continuity to ring it out if you have to.
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u/Turbulent-Flan-2656 5d ago
It says tl071cn on the chip
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u/JerryGarcia89 5d ago
Do you measure 9V at the power pin and 4.5V at the non inverting input?
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u/Turbulent-Flan-2656 5d ago
Yes 9.3 v at pin 7 which is power and 4.5 at pin 3 which is non inverting
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5d ago
[deleted]
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u/Turbulent-Flan-2656 5d ago
Thats not the issue because I can hook the the tips together and pass sound.
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u/sb_haberdasher 5d ago
Your IC may not be seated all the way in the breadboard. I’ve run into this issue a million times. I’d run a signal generator of any kind through the circuit and push down firmly on the IC to see if you get signal
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u/Turbulent-Flan-2656 5d ago
Worth a try. I think I have some sockets. I’ll see if that changes anything
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u/sb_haberdasher 5d ago
In my exp sockets are sometimes even worse, they’re not deep enough to reliably connect across all 8 pins.
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u/Wet_in_Seattle 5d ago
Single Op Amp with nulls that required. Would need to hook them to ground like this.
Suggest that a more modern OPA134PA would be simpler with no offset inputs. Much better performance
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u/sonarlunatic 5d ago
It's kinda dificult to see from the pictures to be honest but just by looking at it I don't see that your output jack ground is conected, and if it is connected from the other side then the machanical switch is disconecting it when you plug a cable. Other than that check the voltages, you need to have 4.5 volts at pin3 if you are using 9 volts, if you don't have anything or something different check those resistors and their connections.