First distortion pedal issues

supermoose2011 · 21st March 2011, 04:31 PM

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

Nigel Goodwin · 21st March 2011, 05:17 PM

The supply connections seem a bit vague?, for a start check the voltages around the opamp.

firechief · 21st March 2011, 05:46 PM

re-draw exactaly what is on the breadboard. Doing so probally help you find the answer.

Minion · 21st March 2011, 11:21 PM

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 .....

wakibaki · 22nd March 2011, 02:33 AM

Quote:

Originally Posted by Minion

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

supermoose2011 · 22nd March 2011, 07:56 AM

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.

geraldfryjr · 22nd March 2011, 02:18 PM

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

poynton · 02:33 PM

What is the op-amp ?

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

21st March 2011, 05:17 PM	#2
Nigel Goodwin diyAudio Member Join Date: Jul 2005 Location: North Derbyshire	The supply connections seem a bit vague?, for a start check the voltages around the opamp. __________________ Nigel Goodwin

22nd March 2011, 02:31 PM	#8
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	What is the op-amp ? The resistance of the meter could be causing the 4.5v to drop.Try changing the 1M to 10K . __________________ If it ain't broke, break it !! Then fix it again. It's called DIY ! Last edited by poynton; 22nd March 2011 at 02:33 PM.

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21st March 2011, 05:46 PM	#3
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	re-draw exactaly what is on the breadboard. Doing so probally help you find the answer.

21st March 2011, 11:21 PM	#4
Minion diyAudio Member Join Date: May 2006	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 .....

22nd March 2011, 02:18 PM	#7
geraldfryjr diyAudio Member Join Date: Feb 2008 Location: Jackson,michigan	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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