Distortion effect
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Author:  mackemint [ Tue Jan 17, 2012 8:30 am ]
Post subject:  Distortion effect

Hello all!
So far I haven't seen anyone coming up with a distortion effect for the Fatman and I thoughtt I was gonna give it a go.
Rectification/diode distortion seems straight forward enough so I figured I'd start there.
I've been using this tutorial on instructables: ... he-design/

In the last step of the tutorial it says you should put it right after an amplifier, and I thought point AD should do the trick.
I put the Signal end to point AD on the PCB and then to ground..
Nothing happens!
I've been through a bunch of diodes, LEDS and whatnot, tested all the components if they work but nothings going on here.
Will this modification even work with the Fatman?


Author:  PAiA-Scott [ Tue Jan 17, 2012 11:03 am ]
Post subject:  Re: Distortion effect

The voltage of the audio signal has to exceed the forward voltage (Vf specification) of the diode(s) for the wave to be changed (clipped). With series connected diodes, their forward voltages add. So, with multiple diodes, or LEDs which usually have a higher Vf than regular diodes, the voltage into this clipping circuit will have to be more than is usual for a line-level signal voltage as it is at point AD (audio output). Try moving it over to the G or where this VCO mix control feeds the VCF input resistor R57.

You might like trying this 4049 clipper/overdrive circuit for smooth sounding square waves from the VCOs:


It is the VCO Ramp to Square Conversion modification from over in this section of PAiA Talk:


Best results are with a 4049 that has a U in the part number suffix.

Author:  mackemint [ Tue Jan 24, 2012 6:14 am ]
Post subject:  Re: Distortion effect

Hmm.. That was kind of obvious I guess, but I figured that a line level signal would be higher than an instrument signal, and seeing that this is meant for a guitar... ^_^

This is interesting, but I was going for something with quite a bit of edge do it.
I'll definitely look into it tho.


Author:  mackemint [ Sun Feb 12, 2012 12:18 pm ]
Post subject:  Re: Distortion effect

Oh just one simple question, do you have a recommendation as to where to take the signal ground from?
The only reference to it I can see in the assembly manual is IC 9:8 and IC11:7..

Author:  PAiA-Scott [ Tue Feb 14, 2012 10:32 am ]
Post subject:  Re: Distortion effect

It should be OK to just pick a spot near any other added wires. Ground/circuit-common originates at wiring points AE/AG/DG. DG branches out to the parts involved with digital and power supply filtering action and AG to those with analog. It will be simplest to access either the Sleeve terminal of 1/4" phone jack used for the audio output, or, the shell of the RCA connectors used for the control outputs.

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