MXR Distortion III/Classic Distortion Mods?

[Martinduo]

Hi! This is an old thread, I know, but still seems like the right place to post this, and it might even benefit someone... 

I have a Distortion III that has been subject to all kinds of modding experiences, here are some of my findings:

To get more gain and a juicier bottom end, place:
R4 1,2 k
C2 4,7 uF

(I also installed a "boost" switch to change between these and original values)

The above mod and a red/yellow led combo at clipping stage will get quite a nice Marshall type distortion.

My other mods:
op-amp 4558P (the original MC33178P is not bad at all, but I prefer this)
C4 reduced to 4,7 nF (more openness and treble control)
C6 raised to 100 nF (more bass)
Switch to disable clipping diodes
Switch to select original diode clipping or red/yellow led clipping

My DIII is already quite versatile (3 switches, each making a big change in sound) - but it still has a hole empty for a miniswitch to add something selectable... Any ideas?

Hey! Great post.
I`m really interested on trying this mods on my DIII aswell, is there a chance to see some pictures of yours?

To see how it`s been done would be very helpfull.

Thanks.

Martin

[Jurbo]

Hey Martin - here's a lowdown of my mods. The modding and experimenting process took its toll on the pedal pcb (for example, removing the opamp was terrible and caused damage), so there are a couple of destroyed copper traces (replaced with wire) and a general messy look, but the thing is alive and stronger than ever, so... 

Here's a view of the controls - I added three switches:



- Gain Hi / Std (Hi gain or Standard gain)
- Lift / Clip (this removes or engages diode clipping - the lift mode is great too, as the opamp screams by itself, too)
- LED / Orig. (if Clip is selected, this toggles between LED clipping (red + yellow) and the original diode clipping)

To understand the changes and the actual soldering points better, you should study the schematic by Gottfried Divos.
In the process, quite a few components have been switched from the top side of the PCB to the bottom side (for a good reason or no reason...).

Gain switch selects either the original R4 + C2 chain (2,2kOhm + 100 nF) or a juicier R4 + C2 chain (1,2 kOhm + 4,7 uF), placed between opamp pin 6 and ground.

The two clipping related switches connect/remove stuff between ground and D1/D2. You can see the original diodes and LEDs on the bottom side.

For easy opamp changing, I installed an 8-pin socket. I like the TI 4558P best.

For easy treble cap changing, I installed a socket for C4 (I actually have 2,2 nF there, not 4,7 nF, giving even brighter sound).

For easy bass cap changing,  I installed a socket for C6 (but the caps I like are so large, that the 100 nF cap (big green square) had to be soldered to the bottom side).

A couple of wires on the bottom side are fixes for broken traces.











At one point I also had an adjustable Big Muff eq installed, with a trimmer (tone pot) inside the pedal and a switch on top to engage/remove the Muff mid scoop. I removed it, because it took too much volume away and I don't know how to design a necessary amplification stage for it. Anyway, that leaves me with an extra hole for a switch, if I decide to try yet something extra for this pedal. By the way, these mods with all the sound evaluations took my one week's spare time, but it was really educative and I learned a lot. And I think the sounds are killer!

[Martinduo]

Hey!

Thank you so much for the pictures!

I will try to do the same to mine.

I really love this pedal, but i feel like it could have more gain, you know?

Will try it and send photos!


Thanx again!

[ddpawel]

Has anyone tried to lift clipping diodes fom bias to ground? Whats happened? Stronger clipping? Or is it wrong in this circuit?

[blooze_man]

Removing the clipping diodes will not result in more clipping. You will get an increase in volume, though.

[ddpawel]

In original version diodes are connected to bias. I asked who connected them to ground, not lift totaly!!! I know what disconnect will do - more volume and op-amp clipping.

[blooze_man]

Ah...a misunderstanding on my part.

[AndrewSeth9115]

could you take off the stock pots and add better quality pots and attach wires to them to make the pedal more durable?

[CynicalMan]

You could, but D-taper pots are hard to find. I think the pots they have in there are fine for durability. As long as the nuts are tight and you aren't rough on the pots, they should be okay.

[zombiwoof]

could you take off the stock pots and add better quality pots and attach wires to them to make the pedal more durable?

My opinion is Don't Fix It If It Ain't Broke!.

Al

[Harold]

I built the Dist III today and I did these mods:

C4: 10nF. The stock 22nF is just too low/middy. I strongly advise against removing this as it will turn the tone knob into a high-shelf knob with way too much highs!
C2: 220nF. Brings back your low-end. Much like the fat mod found on tubescreamers
D1 & D2: Germanium! I tried 1N60 but settled on 1N270's. Removes the modern high-gain sound and adds a vintage character to the pedal.

Overall, I'm quite impressed with this overdrive. Now let's see how long this one will stay on my pedalboard 

[zombiwoof]

I built the Dist III today and I did these mods:

C4: 10nF. The stock 22nF is just too low/middy. I strongly advise against removing this as it will turn the tone knob into a high-shelf knob with way too much highs!
C2: 220nF. Brings back your low-end. Much like the fat mod found on tubescreamers
D1 & D2: Germanium! I tried 1N60 but settled on 1N270's. Removes the modern high-gain sound and adds a vintage character to the pedal.

Overall, I'm quite impressed with this overdrive. Now let's see how long this one will stay on my pedalboard 

Does changing D1 and D2 to germanium lower the output of the pedal?.
Thanks.

[Harold]

Does changing D1 and D2 to germanium lower the output of the pedal?.
Thanks.

Is sure does! Using 2 parallel pairs of germaniums in series should increase volume, but remain "vintagy". I'll be the next thing I'll try!

[hair_energizer]

This was one of the first threads I found on this topic. Although it's very old I want to state s.th. here after trying out various mods. This pedal can be seen as a very effective unit to tighten up your sound using drive level at 0 and output level almost maxed in front of the crunch or overdrive channel of your amp.

C4 mod to a lower value makes sense if u miss some highs or brilliance in your tone. I have done this and kept it at 10nf.

C2 mod to bring back the low end makes no sense at all for people who wanna tighten up the sound. The stock capacitor there makes a very good job. You can tighten up any normal passive humbucker to pure metal tone for broken riffage. Only if you really want to use it in front of your clean channel this mod makes sense.

Reducing R4 will give you more gain but you'll never end up with turning this into a high gain pedal.

Lifting the clipping diodes: Bravo! This gives you an almost mesa boogie - like, slightly wah-like tone and attack.

Some people might still find this thread via search engines, so those are my little bits on this topic.