Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: jedisteve on February 21, 2007, 10:03:36 AM

Title: Having Issue Clipping my signal....
Post by: jedisteve on February 21, 2007, 10:03:36 AM
I am trying to build a distortion pedal and when I hook everything up I only get a clean signal right back.  I am trying to make the signal distort by clipping it symmetrically using two diodes.  If anyone has any idea why I might not be getting the distortion I want or if they can offer any help I would greatly appreciate it...

I have attached my circuit below
Title: Re: Having Issue Clipping my signal....
Post by: ambulance-voice on August 14, 2007, 02:47:49 AM
maybe you should try the traditional 2 diodes to ground clipping configuration
Title: Re: Having Issue Clipping my signal....
Post by: teemuk on August 14, 2007, 05:26:00 AM
First stage gain = 0.8 - 8.8 x

That is generally too low (consider that a nominal output signal amplitude of a pickup is only few millivolts). The attenuator configuration (gain of 0.8 ) may also lead to isntability of some opamps. As a rule of thumb, do not use them at less than unity gain.

12.5k is too low input impedance for a guitar pickup and you will experience a phenomenom that many describe as "tone sucking". You should find a way to make the guitar see at least 500 kohm impedance (preferably 1Meg) - an input buffer perhaps?

Second stage gain: 2 (and limited after diode forward voltage drop)

Again too low, especially considering the low gain of the first input stage. Those diodes will clip at about 650 mV (I assume they're Silicon), so you need about 37 mV input signal to get some clipping (and this is @ max gain). I assume you are already might be getting some slight clipping at signal tops but that's just about it.

Increase the gain, if that won't help then check that you have built the circuit correctly. It should work.