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NEwbie pedal build question

Started by theoptionexplicit, February 03, 2008, 01:45:47 PM

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theoptionexplicit

So I decided to start simple on my first project and build a guitar pedal out of a voice changer toy i've had for a while. I opened it up and it had in/out leads, went online and found a basic true bypass circuit and wired it up. The schematic I used is here - http://www.flickr.com/photos/39729358@N00/2239032639

Unfortunately, a clean guitar signal going into the effected channel is too weak for some reason....seems to be some sort of gate in the circuit. If I plug in a powered source I can dial it in so that I get smooth volume transition between clean and effected, but an electric guitar on its own just doesnt cut it.

I want to remedy this by boosting the signal in the effect chain- IE AFTER it goes through the DPDT switch but BEFORE it hits the toy. I tried doing this with a little radioshack test amplifier, but all i got was terrible deathly screaming noises with no indication of the original guitar signal. I probably wired it wrong and it looped back onto itself or something crazy like that. So basically, I have a simple +/- in and +/- out from that little amp that I want to insert into that specific spot in the pedal circuit. Can anybody help me do this? I'd be so grateful, and this would mean my first successful build.

-Mike


n9voc

Sounds to me like an impedance mismatch causing the amplitude issue.  I have attached an image of a simple preamp, one multipurpose FET and one general purpose NPN transistor.  Overall gain is approximately 5, and the bias is adjusted to have output centered around zero (so no lopsided clipping).  9 volt battery powered.

I hope this helps you! :)