"MXR distortion iii " Any tips for modding and improving tone

[ali1111]

Hi friends, please help me for improving MXR distortion iii for getting better and creamier tones, like fulltone OCD pedal...thanks.

[Ben N]

Welcome, Ali.

The search function is your friend: https://www.diystompboxes.com/smfforum/index.php?action=search2

[Steben]

Afaik, it is one of those rare inverter clipper loop circuits that do not have added opamp clipping. And therefor a nice "object" within the subject of benefits of opamp clipping... perhaps with the rat as opposite. Or is that the II instead of III?
Many low/mid budget SS amps feature those clipping sections as well (Marshall MG, Fender Frontmans....).

What do you dislike? Sterile tone? Not enough "mush"?
Seems to me opamp with diodes to ground (MXR dist +, rat, ...) clippers are rather to be looked at as opamp clipping units with the diodes as "smootheners"....

[Ben N]

There are a number of mods for adding bass, increasing available gain, adding treble. Check the threads.

[Vivek]

I had downloaded this LTSPICE circuit for the DISTORTION III from somewhere on the net.

Is this correct ?

If you propose a mod, I could run that in LTSPICE and share the effect of that mod

[Vivek]

Afaik, it is one of those rare inverter clipper loop circuits that do not have added opamp clipping.

I posted a schematic of a LTSPICE file "DistiortionIII.asc" that I found on the internet.

Is there an error in the schematic ?

[Rob Strand]

Mods here, which I know nothing about.     
https://ironman28.wordpress.com/2015/04/06/mxr-distortion-iii-mods/

Schematic linked to that page.

IMHO, if you want it to sound like another just mod it to *be* the other pedal!  (within the constraints of the available pots)

[Steben]

Afaik, it is one of those rare inverter clipper loop circuits that do not have added opamp clipping.

I posted a schematic of a LTSPICE file "DistiortionIII.asc" that I found on the internet.

Is there an error in the schematic ?

Guess not, it is the dist II that has inverter loop clipping.

[Rob Strand]

Guess not, it is the dist II that has inverter loop clipping.

It still could be the dist III.  The thing that looks like an inverting stage is the tone pot drawn as two resistors (as LTspice doesn't have a pot symbol).

[Vivek]

Like many distortion pedals before it
and many distortion pedals yet to come

The Distortion III makes a mid hump before clipping

The idea is good, since Bass can overpower the other harmonics and make the pedal muddy

While too much treble could make the pedal too shrilly and fizzy.

The Distortion III also has standard trick of increasing the bass cut and treble cut as the gain is increased

Please see graph of the section around U1. It shows frequency response for various settings of the Gain Pot.




Many initial mods for these kinds of pedals are related to

A) remove mid hump
B) reduce mid hump
C) Change location of mid hump

This is quite easy to accomplish by changing 1 - 4 components near the first IC.

[Vivek]

The tone control appears to be another Mid Boost !!!



That does appear odd !!!

[andy-h-h]

Check out the schematics for the Pete Cornish SS-2 and SS-3   basically they are improved MXR distortion +.

[ali1111]

I really like this mod and its awesome tone, anyone can help me for building this mod?
https://m.youtube.com/watch?v=nBvVMlDVAIk

[Vivek]

The first proposed mod at https://ironman28.wordpress.com/2015/04/06/mxr-distortion-iii-mods/ was to change the Tone Control as follows  :

"A popular mod to open up the pedals sound and raise the 750HZ low pass filter is to remove C4 (.022uf) from the circuit entirely or replace it with a smaller value like a .005uf capacitor."





Here is the effect of removing C4 22nf (Capacitor near output pin of 2nd IC) .

The Mid boost circuit becomes a treble boost. It appears that there is no possibility to cut treble. That is still odd !!!

But it's more flexible than another Mid Boost after the earlier Mid boost.

I would recommend this change.

[Vivek]

Ali111

Could you please post the schematic that you followed ?

[ali1111]

I  search for schematic, but nothing found

[Vivek]

Please try that proposed Treble mod

Remove C4 near the Tone control.

After that, we can work on a bass mod.



This is the most popular Schematic on the Internet :

[ali1111]

Thank you for your help

[Vivek]

Also, try the trick I posted before

Put an EQ pedal in front and after the pedal

Play with the EQ till you reach a sound you like.

Then we may be able to propose some mods to try and acheive similar sounds without the EQ

[soggybag]

Does connecting the clipping diodes to VREF sound different from connection g them to GND?

I'm thinking of the Rat. I guess the Rat has a cap on either side of the clipping diodes and that is missing here.