Successful mods for distortion 3 but a couple of questions

[Myampgoesto12]

This thing really gains some wide tonal controls after just a few mods. Here is what I've done so far:

For more treble, next to the IC I swapped C4(22n) out for a greenie 6.8n. Tried just removing C4, way to much treble for my rig.



On C2 for more bass, instead swapping I just added parallel caps - 3 47n's and two 33n's on two leads on the underside of the board for a theoretical total of 307n. I'd still like more bass to come through so I left the heat shrink unshrank.



I was wondering about diode arrangement. Can I just add new diodes on the existing two? Does polarity in such a configuration really change the type of sound? What about just adding a single additional diode to either of the existing two, for asymmetry?

I like this thing better now, but its drive is a bit harsh..not bad just harsh..sorta extra clippy sounding, even before the mods.

Anyway I'm pleased. Hope this helps anyone looking for solutions on this pedal or just mod addicts like me.

Thanks!

[Mark Hammer]

Adding more diodes in series with the existing ones will do things:

• It will raise the clipping threshold such that more "dynamics" will be feasible, but often at the expense of maximum clipping.  So if you like how it sounds with Gain dimed, I'd suggest not adding more diodes, or perhaps only a second pair of Schottkys for a modest shift in threshold.  Another possibility is adding a 3-way single-pole toggle to insert a small resistance in series with the diodes to "soften" the clipping (e.g. 470R, 180R, straight-wire).
  
  Note that increasing the bass content via C2 value also increases the overall signal amplitude hitting the diodes, leading to more crunch, per Distortion-level setting.  For guitar purposes, I can't see much advantage to increasing C2 much beyond 390nf.
• Raising the clipping threshold will also take much of the lid off the output level, much like turning a peak-limiter off.
    That can be a virtue for some players, giving them the option to push an amp harder with a minimally-clipped signal.
    On the other hand, I can understand that some players may find the greater output makes their volume-level settings a little "twitchier".

[Myampgoesto12]

I agree with the C2 comment. At first I just jumpered that cap but from like 1oclock up, the gain control was super gated, much like the blue box with the blend dimed, less finicky though. The notes just died a sputtery death with no sustain hah. I read that increasing that value would accomplish more bass, but I didnt know where to stop, also why I added small increments of capacitance to that part of the circuit. I would like to fine tune for a little more bass though. It still sort of clashes with the bypassed signal. Then again I only got it for my bday to use for heavier stuff when needed.

Its kinda odd that this pedal has such frequency cutoffs. The missing highs and lows really let this thing sing when tapped into..

There's still a lot of volume room left to tap into, but is the volume trade off with the clipping threshold severe enough that it could go less than unity with the bypass volume (perception at least?).  Right now just under 12 level, 11 on tone and gain dimed its pretty equal with bypass volume.

Edit: Also curious about mids control. The tone seems to sweep between cutting highs or cutting lows, which seems typical for single tone ODs, there is room to add additional pots to this thing, could a passive mid scoop be added at the output pot? There's room left in the battery compartment, enough for an inductor at least.

[Mark Hammer]

The Distortion III is really intended as a step up from the original Distortion+. 

One of the aspects of the original Dist+ that some hated and others appreciated was the manner in which bass was lopped off as gain was increased.  That stemmed from use of the ground leg (what would be R4 in the drawing shown here) to adjust gain, rather than the feedback resistance.  This unit uses the feedback resistance which, in tandem with the value of C12, rolls off excessive fizz and top end (and especially hiss) as gain is increased, leaving the bottom intact.  The stock values of R4 and C2, however, still maintain a bass rolloff starting around 720hz, which makes for a thinner sound.  Raising C2 up to 390nf, drps that rolloff point down to 185hz, which is fine for guitar.  Unlike the Dist+, whose gain topped out at 213x, this unit has a max gain of 470x, which applies that gain to both any hum coming into the pedal, as well as any hiss.  So the bass and treble rolloffs are really intended to make the resulting sound usable and tolerable.

The schematic of the Dist III shows a TS-9 type of tone control (though I think C3 should be 270nf, not 27, as shown).  Assuming the corrected value, that stage provides an additional gain of 22x, starting at roughly 1250hz, which seems a little severe to me.  If you look on the AMZ site, Jack Orman has a number of suggested mods to that form of tone control that may be useful for you:  http://www.muzique.com/lab/tstone.htm

[Myampgoesto12]

Ooo! I like that last tone control on that page. I'll have to see what parts I've got layin around for some more mod fun!

I really dig every single response I've had on this forum, which is partially why I chose this forum to be a part of. Lots of info and kindness, even with critical comments. Its all helpful.

Thanks a lot for that link. Haven't come across that.

[Mark Hammer]

Some of us have been on some version of this forum for nigh on 20 years or more.  Jack is one of the originals here, though he doesn't come around as much as he used to.  I have articles of his from the late 70's, though he continues to contribute new and interesting ideas.    A lot of useful stuff on his site. 

[Myampgoesto12]

Man that's awesome. My first stab at modding actually came from an issue I had with a wah I had some 5ish years ago, sealing demon Jr.. Only been a player for 11 years now. My band mate at the time stepped on the cable on the input side. The input jack and the power jack were on a little board together seperated from the main board. After a difficult first attempt that I botched I decided to start digging for info on how to do repairs of this nature, right here is where I've found almost everything I've needed hah.

Its an awesome thing that older cats like that take such roles with a forum like this. Gives guys like me hope. Its a valuable source of knowledge that I deffinately appreciate.

Thanks again. I'm gunna try to emplament that kind of tone control to this thing, maybe even get a switch for adding/changing values for voicing

[Myampgoesto12]

I added a zener in series with one of the existing zeners in the circuit, great sound but it sounded way to similar to my m77. May try different diode types later on as I get them.

I'm happy with the way this this has turned out anyway. Thanks for the input

[Myampgoesto12]

So some time has passed and I finally got to play this thing at around practice volume. I still like the sounds I can get with it, but I can't help but wonder if I can get more saturation out of it, higher gain I guess.  Is lowering R3 an option?

[Myampgoesto12]

Added more capacitance for more bass again but I'm totally thrilled with the pedal now. I can hear the difference in saturation to bass ratio after fooling with it a little more. I'm happy with these results! Thanks again for the help!