Author Topic: Saturation analysis of MXR Distortion +  (Read 2633 times)

ShamaKx

Saturation analysis of MXR Distortion +
« on: February 06, 2015, 09:26:10 AM »
Hello everyone,
My final project preparatory class study is the saturation of a guitar signal and more precisely the distortion from the MXR Distortion +.
In my study, I have already begun to reproduce this wiring diagram on LTSpice software to simulate the circuit and have references measures.
Also, I bought all the necessary electronic components and started reproducing the circuit.

The schematic is the following :



What I would like to do, is separating the circuit into parts and calculate the transfer function of each part to finally get a global transfer function of le circuit.
I think that I could use the Millman's theorem in several points of the circuit  to get the relations and equations.

But I'm not on my results and I have difficulties to find the equations. That's why I need your advice.
Thank you in advance for your answers.
Best Regards.

PBE6

Re: Saturation analysis of MXR Distortion +
« Reply #1 on: February 06, 2015, 12:06:48 PM »
I suggest taking a look at the MXR Micro Amp and Pro Co Rat analyses at the Electrosmash website:

http://www.electrosmash.com/mxr-microamp

http://www.electrosmash.com/proco-rat

It's a brilliant resource for understanding the building blocks of analog guitar pedals.

PBE6

Re: Saturation analysis of MXR Distortion +
« Reply #2 on: February 06, 2015, 12:18:01 PM »
If you're looking to model the clipping behavior of the diodes, I've found that the Shockley diode equation gives pretty good results:

I = Is*(exp(vD/n*vT))-1)

where:

Is = 1x10^(-12) A
n = 1.25
vT = 0.026 V

for silicon diodes seems to work well. Just get your expression for vin in terms of vD, then solve for vD iteratively.