The Ultimate Boss DS-1 Mod

28 December 2007

Ideology Behind the Mod:

I bought a DS-1 with the notion to mod it. I knew what it was like stock so I wanted to see what I could do with it to try and improve the sound. I figured I would perform the well known Robert Keeley’s mod and it would be great. Well I did the Keeley mod and wasn’t all that impressed. I found the pedal had too much gain (it was always like that), it lacked mids, the tone control was shrill, the bass was flabby loose and the tone tended to get fuzzy. The pedal was also not very versatile in it’s tonal range.

I set out to modify the pedal to address my needs and fix the issues listed above. I have now incorporated some of the Keeley Mods, other mods from people and my own. I must say I really like the result. After hours of tweaking my Boss DS-1 it is now exactly what I wanted it to be. It has great response to your picking, it is very smooth, the lows are round and tight, it has a lot more mids, less gain, is very tube like sounding and the tone control is also so much nicer.

I tried to model the modified sound roughly after a Tube Screamer. It has that classic Tube Screamer style tone with a slight mid hump. It is slightly different in the sense that it does have a bit more gain (good for more modern style music) and more dynamics.

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).

C1, C10, C11: 0.047µF
C2: 0.68µF
C3, C5: 0.068µF
C4: 470pF
C7: 220pF
C8: 0.47µF
C9: 0.47µF
C12, C13: 0.1µF
C14: 1µF NP (non-polarized)
Solder a 47pF cap across one of the clipping diodes (D4 or D5).

R13: 2.7KΩ
R39: 20KΩ
R16: 1.5KΩ (could wire a 5KΩ pot here for a mid control)
R11: 33KΩ
R9: 1KΩ
R17: 6.1KΩ

R35: 2.2KΩ
D10: 5mm Water Clear High Brightness Blue LED (this is a new indicator LED)

D4: Wire a DPDT (On-On) switch to select either a 3mm Water Clear High Brightness Red LED in series with 20KΩ resistor or a 1N270 germanium diode. You can add another diode in series with either D4 or D5 for asymmetrical clipping and a bit more odd order harmonics and overtones.

Regarding the clipping section (D4 and D5) the DS-1 utilizes a hard clipping diode setup. The pair of diodes goes from the output of the op-amp to ground. When the signal coming out of the op-amp exceeds that of the forward voltage of the diodes the diodes conduct (clip). This clipping is what causes distortion. With this in mind you can see how the forward voltage of the diodes has a large impact on the headroom and distortion tone of the pedal.

Silicon diodes (stock) will give a tight high gain modern sound. LEDs have an open type sound with less distortion but quite uncompressed (some call LEDs tube like sounding). Germaniums diodes have the lowest forward voltage of the diodes mentioned above and as a result they provide the most clipping (distortion).

The switch in my mod allows the user to select either a germanium diode or an LED for D4. While D4 is switchable D5 always has a silicon diode (1N4148). The switch then allows the user to either select germanium diode with silicon diode or LED with silicon diode. This provides two very unique sounds. In the germanium position the tone is thick with lots of distortion and overtones. The LED position provides more headroom with a more tube like sound.


I have heard a few people say that after they modified their DS-1 to Keeley specs or other modifications that it was good for lead but not rhythm playing. With these mods chords are tight and not flabby. This pedal can now be used for any style of playing. I also found the DS-1 is best used with guitars equipped with humbucker pickups. With single coils it still sounds good but it is a bit less compressed and can get a tiny bit loose. To counter this the tone control can be rolled up to tighten things up.

Overall the mods take a very cheap generic pedal and turn it into a good sounding distortion that is very useable and in a variety of settings/styles. The sound is full, dynamic and rich. The pedal is no longer thin shrill and with too much gain. Instead the tone is more lively and suited to more styles of music/playing.



The Keeley DS-1 Mod
DS-1 Building/Modifying
AMZ DS-1 Mod

{ 1 comment… read it below or add one }

Detlef November 12, 2016 at 20 h 48 min


I just saw that and what you said sounds resonable to my ears. I also think that the ds-1 has 2 much gain.
I wonder if there are any sound file`s of your mod!

Uhhps!! 2007 – maybe you`ll get it alive. :)


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