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Old 21st March 2011, 04:31 PM   #1
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Default First distortion pedal issues

Attached is the circuit I am using for my first stomp box build. I've gotten rid of D1 and D2 and made D3 and D4 always switched in. At the moment its been built on the breadboard several times and I haven't been able to get any sound out of it . Any tips on how to fault find or anything that anyone can spot wrong with the circuit would be very much appreciated. Cheers
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Old 21st March 2011, 05:17 PM   #2
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The supply connections seem a bit vague?, for a start check the voltages around the opamp.
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Old 21st March 2011, 05:46 PM   #3
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re-draw exactaly what is on the breadboard. Doing so probally help you find the answer.
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Old 21st March 2011, 11:21 PM   #4
Minion is offline Minion  Canada
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I agree that the schematic is vague , it doesn"t show how to get the Bias voltage , that has been left out of the schematic .....
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Old 22nd March 2011, 02:33 AM   #5
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I agree that the schematic is vague , it doesn"t show how to get the Bias voltage , that has been left out of the schematic .....
Yeah, there's no indication where the 4.5V is supposed to come from. Connect the 1M resistor at the non-inverting (+) input on the opamp to the 9V rail and connect another one from the same input to ground.

You should get something out of it.

w
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Old 22nd March 2011, 07:56 AM   #6
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Thanks for your replies. Sorry I should have put the bias diagram on it too, here it is. I built the bias bit first and tested that out and the voltage does end up being 4.5v however, when I connect the op amp and test the voltage between pin 3 and ground it has dropped to 0.71v. Not sure if its supposed to do that because I am a complete beginner at this.
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Old 22nd March 2011, 02:18 PM   #7
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Your audio ground (input and output) should be taken at the +V/2 (4.5v) point, and only the -v of the opamp connected to neg supply along with the bias circuit. jer
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Old 22nd March 2011, 02:31 PM   #8
poynton is offline poynton  United Kingdom
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What is the op-amp ?

The resistance of the meter could be causing the 4.5v to drop.Try changing the 1M to 10K
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