New Build Doc: "Build Your Own DS-1 Distortion"

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Link to the new post, in which implementation details of the MIJ-Mod are given: http://www.diystompboxes.com/smfforum/index.php?topic=64927.0.

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Folks, if you're building a DS-1 from this doc, please check the value for C8 in the 'Stock DS-1' and 'True-Bypass DS-1' schematics.  C8 is supposed to be 0.47μF/50V for the post-1994 DS-1 and 1μF for the MIJ-Mod and MIJ-Mod PLUS DS-1.

We had some confusion early on about this value.  Unfortunately, the value for C8 remained documented at 1μF in many of the versions of this doc so far.  I think I've finally got all this worked out, so please grab the latest version of the doc to pick up the latest corrections.

Sorry for the "version hell", but this often happens when you have multiple contributors working on a technical document (who have busy full-time jobs.) 

-Brett

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Greetings once again!  I've come up with the third and likely final mod in the MIJ-Mod series.  It's called the "Mondo-MIJ" and it is a high-fidelity version of the "MIJ-Mod" that builds upon the previous two "MIJ" mods.  The resulting distortion is really exceptional, particularly considering that it is coming from the humble DS-1.  I've demo'd the prototype to a couple of my guitar buddies and they were very impressed with the Mondo-MIJ by itself.  They were especially gracious towards it when comparing it to the stock pre-1994 DS-1, stock post-1994 DS-1 and MIJ-Plus DS-1 pedals I let them play side-by-side with the Mondo-MIJ DS-1.  (I'm now building additional Mondo-MIJ DS-1 pedals for them...an understandable consequence and a flattering result at the same time.)

The original "MIJ" mod was designed to replace only the minimal number of components necessary to make the post-1994 DS-1 sound like the pre-1994 MIJ vintage DS-1. The "MIJ-Plus" mod was designed to remove some of the "fizz" from the "MIJ" mod by increasing the proximity to clip in the D4/D5 clipping diodes. The "Mondo-MIJ" mod is designed to bring a higher fidelity sound to the "MIJ"-type mods through the use of film capacitors, an upgraded op amp and a more sophisticated clipping circuit. Admittedly, this is probably the last of the "MIJ"-type mod series. To extend the mod much further than the "Mondo-MIJ" will take the pedal in a direction that will likely be inconsistent with the tone shape and note articulation that endear the original MIJ DS-1 (and hopefully "MIJ" modded) pedals to guitarists worldwide.

You can find the "Mondo-MIJ" mod instructions in the 2-26-2008 version of the 'Build Your Own DS-1 Distortion" document located here: http://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf.  Pages 18-21 are the specific pages related to the "Mondo-MIJ".

NOTE:  If you have questions how to wire "Part 3" of the Mondo-MIJ, please post on this thread and I'll answer them as best I can.  The new clipping circuit in the "Mondo-MIJ" is a bit more complex than your average "diode swap" mod, but the resulting distortion is well worth the effort.  Jack Orman's articles on alternative distortion saturation controls are to be thanked for giving me the inspiration for the clipping circuit mod in the "Mondo-MIJ".  (Thanks, Jack!)

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New minor mod to report today, the "PHLAT" Mod.  This mod is an alteration to the low-pass and high-pass filters that feed the TONE control of the DS-1.  The intent of this mod is to give the user the option to switch between the stock, scooped-mids tone and a flatter tone shape that will help keep the tone full-sounding at lower DIST settings.

The stock DS-1 TONE control has a low-pass filter with a corner frequency of 234 Hz and a high-pass filter with a corner frequency of 3290 Hz.  This produces the classic DS-1 scooped mids tone that allows the harmonics produced by the clipping diodes to be more prominent, giving it a heavily-distorted sound.  The PHLAT Mod moves the corner frequencies of both the TONE low-pass and high-pass filters to 1064Hz.  This change results in the mid frequencies to jump out more, resulting in a noticeable volume increase, as well as boost in sustain.  The resulting distortion is less harmonically rich than the scooped tone, but has a more vintage amp tone that works well with blues and country riffs at lower DIST settings.

I've added the PHLAT Mod to the 'Build Your Own DS-1 Distortion' doc and you can find it in the usual place: http://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf.

[drewl]

Hey, nice work.......I read the doc. so I don't have any stupid questions.
You answered them all!

[flo]

Very nice document. Thanks a lot! I wanted to build one and fiddle with it. This will help me along perfectly!

[mattpas]

How close is this design to the Tonepad FX DS-1 PCB?

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How close is this design to the Tonepad FX DS-1 PCB?

There are quite a few differences between the True-Bypass DS-1 in the 'Build Your Own DS-1 Distortion' doc and Francicsco's DistoUNO DS-1 work-alike.  If you compare the schematic for the TB DS-1 on Page 8 of http://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf with the DistoUNO schematic, you'll see there are a number of differences in the component values.

Why the differences?  Well, Francisco was designing a PCB that would allow the builder to use either a TA7136P (the original DS-1 single op amp) or a 4558-type dual op amp, which by itself is a very cool feature.  When miqbal did the schematic/PCB for the Stock DS-1, he wanted to exactly match the post-1994 BOSS DS-1, except use a DIP8 dual op amp pinout.  When I did the TB DS-1 schematic/PCB, I wanted to preserve the stock layout/component numbering so that folks could make a TB version of the DS-1 that was still moddable with all the DS-1 mods floating around on the Internet.  The TB DS-1 schematic preserves everything in Miqbal's Stock DS-1 schematic, except it removes the input/output buffers and the flip-flop switching circuit.

I've never built Francisco's DistoUNO, but I'm sure it rocks (just like everything else I've bought from him.)  The DistoUNO is a great choice if you want to build a DS-1 with the original TA7136P op amp.  Miqbal's Stock DS-1 is great if you want to build a BOSS DS-1 replica that uses the more readily available DIP8 dual op amps.  My TB DS-1 is great if you want a true-bypass DS-1 that is very nearly stock, plus it has the option to incorporate Keeley's Seeing Eye/Ultra mods included right in the PCB.

So in the end, you'll have to decide which is best for you, but that's a quick rundown of the differences between the three DIY DS-1 layouts.

[drewl]

Okay, I do have a stupid question.
What is the "seeing eye mod"?
Is it using an LED for a clipper that is viewable from the top so it will light up as it clips?
just my guess thanks......hard to keep up with all this wackiness.

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Okay, I do have a stupid question.
What is the "seeing eye mod"?
Is it using an LED for a clipper that is viewable from the top so it will light up as it clips?
just my guess thanks......hard to keep up with all this wackiness.

Yup, that's part of it, but there are additional cap changes as part of that mod.  On Pages 13-15 in the BYODD doc (http://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf), there are full details regarding Robert Keeley's Seeing Eye and Ultra mods.  In a nutshell, Mr. Keeley drills out the 'O' in the 'TONE' lettering on the DS-1 and installs a red LED in place of the D5 clipping diode.  The fact that you can see the D5 clipping LED illuminate in the 'O' of 'TONE' is the "seeing eye" part.

For the Keeley Ultra mod, he replaces the D4 diode with a series combination of a red LED and 1N4148 diode.

As I mentioned before, there are other cap/resistor changes that make up the rest of those mods, but you can read about those either in the aforementioned BYODD doc or on Keeley's website at http://www.robertkeeley.com/audio6l6/dstech.html.

[DiamondDog]

Great work, Brett and Miqbal!

Can I make one suggestion regarding the 'straight' DS-1 layout, though. The way it is set up at the moment, you have to heat up a pretty substantial area of the gound poor to solder effectively, and when you do it's a messy result. If your design program allows it, it is easier if you have a solder pad in and isolated from the pour, which is then connected to that pour. Confused? Let me try this way:

* = pour
o = pad
- and | = connections

*******
*******
**  |  **
**_o_**
**  |  **
*******
*******

That way you only  have to get the pad up to temperature, not a large pour, and you don't compromise connectivity. I hope that makes sense.

I use Eagle and it has an option to do it; I don't know what program you use.

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Great work, Brett and Miqbal!

Thanks.

Can I make one suggestion regarding the 'straight' DS-1 layout, though. The way it is set up at the moment, you have to heat up a pretty substantial area of the gound poor to solder effectively, and when you do it's a messy result. If your design program allows it, it is easier if you have a solder pad in and isolated from the pour, which is then connected to that pour. Confused?

Well, a little confused.  When you refer to the 'straight' DS-1 layout, are you referring to the Stock DS-1 layout or the True-Bypass layout?  Muhammad designed the Stock DS-1 schematic and layout on Eagle CAD.  I did the True-Bypass DS-1 schematic and layout using Microsoft Visio 2007.

The traces in the Stock DS-1 layout are, on average, bigger than those on the True-Bypass DS-1 layout.  Muhammad tried to match the trace shape and size of the original BOSS traces as possible.  (You can reference a solder-side image of the BOSS PCB here: http://i76.photobucket.com/albums/j23/overdrivespider/step03_05.jpg.)  One possible solution to excessive solder flow would be to apply a solder mask, as BOSS did with similar-sized traces on the post-1994 DS-1.

[WGTP]

Very well done.   

It appears to me that the first "gain" stage after the input buffer and switching is very similar to the Big Muff Pie stages without diodes.
Looking at BMP mods, the bias resistor from the collector to +9v varies from 10k to 15K, with some versions using different values in different stages.  This would seem to be a value to investigate as it effects the bias, gain and symmetry of the waveform.  Depending on the transistor being used, it may be optimally biased or not.  A 25k trim pot might be useful.  This is R8. 

Also the resistor from the emitter to ground R9, varies in the BMP from 100 to 680 (some mods bypass it).  In the DS-1 it is 22 which would seem to have increased gain and also limit the swing of the waveform on one side creating asymmetrical distortion, I think.

Has anyone experimented with this stage?

I guess the first op amp is a buffer between the BMP type stage and the "drive" stage or second op amp.  I haven't tried the DS-1 without diodes, but I suspect it will have lots of distortion from the op amp being overdriven before the signal gets to the diodes.  This is why the op amp selected has a significant effect on the tone.  Other suggested op amps, are the OP275, TLC2262, NE5532, 4559, TL052, etc. There are hundreds.   

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Very well done.   

Thanks.

I guess the first op amp is a buffer between the BMP type stage and the "drive" stage or second op amp.  I haven't tried the DS-1 without diodes, but I suspect it will have lots of distortion from the op amp being overdriven before the signal gets to the diodes.  This is why the op amp selected has a significant effect on the tone.  Other suggested op amps, are the OP275, TLC2262, NE5532, 4559, TL052, etc. There are hundreds.   

I'll be rebuilding a couple of DS-1 pedals in the immediate future, so before I rip them all apart, I'll pull the D4/D5 diodes and see what they sound like with both the M5223AL and newer NJM3404AL with no clipping diodes.  I'll let y'all know what I find out.

[Andre]

Thanks for a very nice and well documented project.

Here's some pics of the one I built in a Boss like enclosure.



André

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NICE job Andre. 

Also the resistor from the emitter to ground R9, varies in the BMP from 100 to 680 (some mods bypass it).  In the DS-1 it is 22 which would seem to have increased gain and also limit the swing of the waveform on one side creating asymmetrical distortion, I think.

WGTP, educate me here:  BMP?  And why 22?  Seems like a rather random value.  Why not just bypass it?   

[WGTP]

I'm not an expert on these type of stages (or any other for that matter), but I THINK that the lower the resistance, the higher the gain and more asymmetrical the distortion.  I thought it looked familiar so I checked the BMP stages and there it was.  I think Boss wanted to drive the op amp stage pretty hard and 22 ohms provided what they were after.  By-passing that resistor probably provides no hope of a clean signal getting thru, thus limiting the possibilities for semi-clean tones.   

I just recalled the AMZ Overdrive Pro has a similar first stage with a 150 ohm reisistor, but no cap parallel to the 470k resisitor.  This cap rolls off highs.   

[ayayay!]

I'm sorry WGTP.  I wasn't spefic:  what does BMP stand for? 

[DiamondDog]

I'm sorry WGTP.  I wasn't spefic:  what does BMP stand for? 

"Big Muff Pi". You will find the BMP's single-knob tone control in a lot of circuits. Check out the workbench or whatever at Jack Orman's site for lots of variations on it.

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Thanks for a very nice and well documented project.

You're welcome.  I'm glad you found it helpful, as I use it often myself.

Here's some pics of the one I built in a Boss like enclosure.

Very nice build, André.  Looks cleaner than even BOSS makes 'em.