Help Mod my crappy DOD pedal.

[petemoore]

   im jsut salvaginf some of these parts in hopes of putting together my own overdrive.
  Sorry to be a skeptic, but ^ seemed a best alternative to me.
  a whole lot of messing about with limited results *might not be the outcome of your efforts with such circuits.
  If you're not fond of the sound...of a whole bunch of stuff thrown in to make a very adjustable and severe distorter...you might find a smaller portion [fragment's] of that circuitry does something useful...'longview' IMO.
  The usefulness of "WOW" novelty type circuits that fundamentally and drastically change harmonics and EQ, have great novelty factor that can wear off, sometimes quickly...very interesting and fun to dial around on for a time or two, then when all the dialing never gets you 'there'...the 'POC" aspect comes into view.
  Is there a 'Metal Guy' [popular artist] that actually uses this type of thing?...maybe they have shed light on 'how to use' one.

[James V]

You should be able to use them (the opamps, that is) in quite a few circuits. I think that the other IC is being used to do the bypass switching, and would be less useful to you. I'm certainly no expert though, and it's not really worth you time (in my opinion, anyway) to desolder them. Because they are bipolar input opamps they might not work so well in a circuit that's designed around a FET input opamp, although I think they'll be fine in most circuits you might try.

Usually if I'm trying out a new idea or something I use a TL72 (or a TL82), because it's a cheap and generic FET input opamp which will work pretty well in about 90% of stompbox circuits. You can pick these up  from high street electronics places like Maplin (in the UK, or I believe Radio Shack carries either the TL82 or TL72 in the US). There's a little less to worry about, at least for people like me who don't know what they're doing, using FET input opamps.

BTW, if you're new to all this, you might want to check out some articles written by some of the forum regulars which will give you an idea of what's happening in distortion/overdrive circuits. The "technology of" series at geofx are great (in fact, check out the rest of the site too, if you haven't already), and the "cook your own distortion" page at general guitar gadgets (again, check out the rest of the site) will also help you get a feel for what does what in basic distortion circuits.

http://www.geofex.com/fxtech.htm

http://www.generalguitargadgets.com/richardo/distortion/index.html


This is just my opinion, but I think you'll have more luck building a much simpler project from scratch, rather than trying to modify a fairly complex circuit that we don't even seem to have a schematic for. It's easier to see what's going on in a simple circuit, and what impact a change will make, than in a complex one.

But good luck with whatever you do!

[Paul Marossy]

Those extra parts just have to do with the electronic bypass switching. (which isn't shown on that schematic)

[Stompin Tom]

I tried several things this weekend on my own dumb dod distortion pedal and had the same results as shanter.  crap crap crap!

I think I'm going to take everyone's advice and put together my own circuit... and maybe even use the same ugly box, if it fits. 

A little off topic, but has anyone put together a relatively simple fuzz circuit they'd recommend?  I've seen several schematics and projects floating around on different sites, but i'm not sure which to try...  I'm drawn to Tim Escobar's take on the Harmonic Perculator:

http://www.home-wrecker.com/harmonic.html

Anyone experimented with it?

[MartyMart]

No, but his "Tripple Fuzz" is a LOT of fun !!

Marty.

[Eric H]

when i played high notes it sounded like i was sticking the soldering iron in my ear.

I hate it when that happens.

[petemoore]

  For opamps...i suggest...
  Liquid Drive [Fuzzcentral] it's like DIST+ but different...real nice
  Tube Reamer {ROGroove] is a stripped down TS, livlier sounding I think.
  These are basic OA Clipper [one is diodes to ground... 'LD or DP' the other is diodes in the feedback loop of opamp "TS or TR'.
  the addition of a booster in front makes harder distortion sounds, I prefer Bipolar like LPB or Jfet like many booster schematics use.

[Paul Marossy]

Tim Escobar

Uh, I think you mean Tim Escobedo. 

Oh well, I guess that circuit is one that you either like or don't like. Doesn't seem to be too much in between...

[Stompin Tom]

oh... uh... i knew it was Escobedo... 

sorry tim, wherever you are...

I've tried Theremaniacs harmonic perculator clone and thought it sounded great with my tele (Shellac anyone?).  Strangely I didn't like it nearly as much with humbuckers.  I'm curious to a/b Tim's version with the clone... 

[Paul Marossy]

Just for the record, I stumbled upon a full schematic for the DOD FX86

http://www.geocities.com/alan_probandt/schematics/FX86_DeathMetal.gif

[Transmogrifox]

Something I noticed is the DOD Death metal pedal is identical to the Boss Metal Zone all except for the last stages where the MT-2 has the sweepable mids.  There are several resistors and capacitors you would need to replace to make this mod, but it does not require any changes or hacks to to the circuit board.  What you will have is a Metal Zone with a non-sweeping mid.

This is an old post, so it's just fodder to resurrect for those who have an old Death Metal pedal hanging around

[Paul Marossy]

Something I noticed is the DOD Death metal pedal is identical to the Boss Metal Zone all except for the last stages where the MT-2 has the sweepable mids. 

Very interesting! I use my Metal Zone only to get these nice singing leads. I can't imagine using it for anything else, though. I did spend a lot of time tweaking the EQ to get some good tones out of it. But I found a sweet spot that works well for me.

[Caferacernoc]

Yeah, I've got a DOD Classic Tube. It's crap. The schematic seems simple enough. It looks like a tube screamer/Dist+ hybrid in that there a clipping diodes in the feedback loop and going to ground. I've altered stuff, removed diodes, more bass cut....... It's just not good. I eventually took out almost all it's distortion capability so it's really a clean boost now. I'm guessing the op amp just has ugly clipping on it's own and that's why I couldn't get it to be a nice tube screamer or dist+ when I was modding it.

[Paul Marossy]

I'm guessing the op amp just has ugly clipping on it's own and that's why I couldn't get it to be a nice tube screamer or dist+ when I was modding it.

Yeah, it's probably opamp clipping that you are hearing. That usually doesn't sound very good. You could mess with the gain of the opamp to maybe clean it up a little bit.

[Ben N]

Clipping is a form of limiting. So if you take out the clippers, the signal level going to subsequent stages is way higher than they are intended for, and you are likely to get opamp clipping. There is a thread elsewhere, er, at another DIY site, about the Timmy overdrive, in which someone suggested removing the clippers for a clean boost, and this got nixed by Paul C himself, because the gain of the clipping stage without the clippers would definitely overdrive the second stage, which was designed to run clean, and he felt this would not be pretty. The way to compensate is either to raise the bridge or lower the river--cut the gain cliping stage(s) or increase the headroom in the training stages.

[Paul Marossy]

Clipping is a form of limiting. So if you take out the clippers, the signal level going to subsequent stages is way higher than they are intended for, and you are likely to get opamp clipping.

Good point. But clipping diodes are distorting the signal, too, and then that is being sent to an opamp where it might be distorting it even more. I mean those diodes are chopping the peaks of the sine wave off and some of that "information" is lost. That's distortion.

So depending on the circuit, you might need to remove the clipping diodes and tweak the gain of the opamp. Tweaking the opamp gain is probably a given in any case.

[Transmogrifox]

Yeah, I've got a DOD Classic Tube. It's crap. The schematic seems simple enough. It looks like a tube screamer/Dist+ hybrid in that there a clipping diodes in the feedback loop and going to ground. I've altered stuff, removed diodes, more bass cut....... It's just not good. I eventually took out almost all it's distortion capability so it's really a clean boost now. I'm guessing the op amp just has ugly clipping on it's own and that's why I couldn't get it to be a nice tube screamer or dist+ when I was modding it.

It looks like the first drive stage is the culprit.  This thing looks really like a bad idea, IMHO

I'm not sure what things you have tried already, but here's what I would do if given this pedal:

My first try without hacking the circuit board would be to change the capacitor in the first clipping stage feedback loop from 1uF to something no larger than 0.33uF, but experiment with a range of values between 1nF and 330nF.  I'm guessing something at nearly 10nF would give the most useful range...although you may also want to increase that 680 ohm resistor to something between 5k and 10k.  In this case, there will only be a sweet spot available.  That 500k pot in there is the devil.  You may wish to decrease its overall value by putting a 100k or something in parallel with it, and reduce that resistor in the feedback loop.

As this pedal is, it creates a lot of wide-band gain and has the best high-pass condition at max drive, 235Hz.  This is where it should be at min drive for a tighter sound.  Then when the 500k pot is even mildly increased...say, to 10k, basically the high cut-off is well below guitar frequencies and all you have is ugly fuzz...either way is ugly fuzz in this pedal.

Anyway, the diode configuration is not the problem, it's that goofy gain stage. 

Ideally I'd hack into the circuitboard and change this gain stage to something more like the TS with the pot between the output and inverting inputs of the op amp, then with a fixed resistor in the grounded end of the feedback network.

The LF353 is not the most wonderful op amp, but I don't think that's the real problem.