The Ultimate Boss BD-2 Mod

28 August 2008

Ideology Behind the Mod:

After playing with Boss BD-2 for a while I was not impressed. No blues player would ever need the gain this unit puts out. Even the minimum gain was blowing my head off. This pedal was very shrill sounding, I couldn’t use the tone control at all, way too piercing. There was also fuzziness and buzz when the gain control went past noon.

Anyways I like bright clear tones and fat tones and I am not a huge fan of over the top gain. With this is mind I started moddifying the pedal’s circuit.

Before you Modify your Pedal:

Before you go slap happy tearing out components and “modding” away. Though this is not an intensive mod it still involves quite a bit of work. To make sure your pedal sounds great and works at the end I recommend testing the pedal after you finish desoldering and soldering in four or so new components. That way if your pedal doesn’t work it’s easier to find the problem. I did this but with every component. I did this when I was developing the mod and wanted to hear things rather than make sure they worked.

A hint for removing Boss’ industrial lead free (RoHs) solder. First heat up the joint so the solder melts, then heat again and apply a bit of your own lead solder (i.e. 60/40). After this is done you can go about removing the solder with your desoldering braid or pump.

The Modifications:


All part numbers refer to the schematic above (part numbers are printed on the PCB).

R21: 2.7K (could wire a 5KΩ pot here for a contour control)
R34: 5.6KΩ
R38: 220KΩ

C8: 0.0047µF
C14: 0.1µF
C16: 0.01µF
C17, C19: 0.01µF
C18: 0.01µF
C19: I didn’t touch this cap but for a mid boost remove this cap. More mids, more gain.
C27: 0.01µF
C34: 0.082µF
C35: 0.047µF
C100: 0.047µF
C101: Wire a DPDT (On-On) switch on C101 to select between a 0.033µF and a 0.068µF cap. This switch allows you to go from a normal tone to a fat thick tone.

D3: 1N4002
D7, D8, D9, D10: 3mm Water Clear High Brightness Red LEDs. These are clipping diodes. LEDs make the pedal fatter, tighter and more compressed. I also find they add some dynamics to the pedal. They also clip much less than a standard diode so you get more headroom!

The next part of the mod is what I would call a Hi-Fi mod. No values of parts are changes. Instead the material of certain capacitors (di-electric) is changed to a nicer better sounding material. Don’t cheap out here and not do this part of the mod. Without this part I seriously doubt the pedal would sound so good. It may not be the most interesting part of the modifications but it’s worth it.

Use all Silver Mica caps here.
C26: 220pF
C21, C23: 47pF
C20, C25: 470pF

Use tantalum capacitors here
C1, C6, C7, C12, C13, C15: 10mF (16V or higher)

This part of the mod is great. All the fuzz and fizzeyness when the gain control was turned up was gone. Clarity was increased and the pedal had more dynamics and felt like it responded better to my playing.

R39: 2.2KΩ
D10: 5mm Water Clear High Brightness Blue LED (this is a new indicator LED)


After performing the above mods the pedal sounds much better. It is nice and clear and warm or with a flick of a switch it is fat and compressed both ways retaining excellent clarity though. The tone control is totally useful now and much more versatile. The gain control is quite useable and one can actually have a low gain sound now.

You can set the gain so low the pedal can be used as a straight up clean boost. It can still do some great crunch/post crunch tones but no more metal. It responds to my touch and feel. I tested this pedal with nine different tube amps, one solid state and three guitars and it sounded great with all of them, mission accomplished.

A cheap pedal turned into a cheap very useable pedal!


{ 15 comments… read them below or add one }

Flavio February 18, 2014 at 9 h 59 min

I, i made tus mod to the bd-2, but the gain has increased to the point ti cant be used as a clean boost, i change c19 to 0.01mf, do you think this is the problem?


cmoir February 18, 2014 at 22 h 14 min

Hi Flavio,

I don’t think that cap change is the problem. Sounds like something else is the issue. Try to retrace your steps and put the pedal back to stock.


frederic_rv April 7, 2015 at 20 h 23 min

Hello, I deeply thank you for sharing your mod specs that I carried out on my BD-2. Two questions:
1/ As 470pF Silver Mica is unavailable in my country, I had to use ceramic caps instead. May I resort to the closest available value in Silver Mica which is 500pF or 390pF? Or should I leave it that way (ceramic 470pF)?
2/ Every time I switch into normal or fat tone thru the on-on SPDT toggle, I can hear a sharp clicking noise. Have I done something wrong? Should I have put a DPDT instead? If so, would you explain its diagram?
Best regards


cmoir April 7, 2015 at 22 h 22 min

1. Use either the 470pF cermaic cap or the 500pF silver mica cap, both are fine. 500pF would be my choice.

2. The clicking noise is capacitor discharge, perfectly normal. Try putting a 1M resistor from the middle lug of the SPDT to ground. Or replace the SPDT with a DPDT and wire the caps with that.


frederic_rv April 8, 2015 at 8 h 46 min

I thank you. Few seconds after a note or a chord, I noticed some light scratchy sound before the sound definitely vanishes. I also experienced it with your DS-1 mod. Don’t get me wrong! Both are great. These are the best mods I ever had the schematic of. Well balanced, distortion starting at 2 o’clock instead of 9 with other stock pedals. Anyway we’re talking of distortion pedals and this happens with other stock ones but this is thinner. Is it a logical outcome of an OD/DS pedal mod or am I too sensitive?
Kind regards


cmoir April 8, 2015 at 22 h 27 min

That should not be happening. Sounds like a cold/bad solder joint.


frederic_rv April 9, 2015 at 8 h 37 min

Cold solder joint is my curse. I’ll check out every joint. Thanks again!


frederic_rv April 15, 2015 at 22 h 17 min

Hello, something odd happened. After playing my BD-2 few minutes, I bypass it and sound dies away. I switch it on again and sound comes back. In a way ot another, sound eventually disappears. One cap seems to be leaking. I changed the 6 tantalum caps you advised for the mod but I still have the problem. I cannot replace every cap on its PCB. Any clue? I have the foreboding that I lost my stompbox. Bye!


cmoir April 15, 2015 at 23 h 46 min

Check the polarity of the caps you replaced! Sometimes it’s hard to tell the polarity on tantalums.


frederic_rv April 16, 2015 at 12 h 07 min

To my knowledge, this vanishing sound looks like it. I then checked their polarity out. I even replaced them by the stock polarized electrolytic caps but the failure remains. I’m afraid it’s beyond my skills. Too bad!


frederic_rv April 17, 2015 at 20 h 16 min

Hello, I gave it one more try. I reversed to stock version and the problem is even more obvious. When and only when bypassed, the sound goes by within one sec. Otherwise everything seems to be OK. I cannot bypass this pedal! Any lead I should investigate? I mean, is there a specific bunch of caps and/or resistors I should check out according to your experience?


Dany April 25, 2015 at 22 h 26 min

Hi there, you specified 1N4002 for D3 and red LEDs for D6, D8, D9 and D10 as for the clipping. I’m wondering which other diodes I might solder instead. I very much enjoy plexi tone and I still have one Ge diode 1N34A, few 1N4007s and 1N4148. Where would my one 1N34A suit better? D6? And what about 1N4007s? D7 and D8? Many thanks for your help. Dan.


cmoir April 26, 2015 at 23 h 17 min

The best thing you can do is socket the diode positions and try as many diodes in as many positions as you can.

That said to try and get a “Plexi” tone I would keep D8, D9 as red LEDs. Make D7 and D8 either 1N4007 or 1N4148. You could also add a 1N34a in series with D1.

note there was a typo in the original post, D7 should be changed not D6.


riley September 1, 2016 at 0 h 58 min

To clarify on the DPDT switch part, are you replacing the one capacitor (C101) with 2 capacitors and a switch,
Allowing the switch to switch between the two capacitors?


cmoir September 4, 2016 at 1 h 26 min



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