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Boss DS-1 CSG mod

There are many legendary pedals out there, the Boss DS1 is probably one of the most popular distortion pedals of all time. Itís been around for a long time and has been on the pedal boards of many of the greatest guitar players...

...but itís hardly ever heard as the stock unit.

The DS1 is a pedal that is regularly modified to achieve improved sounds and can be tweaked to give many different sounds.
Iíve put together a list of changes to the circuit that I think will improve the pedal, tailoring the gain, and particularly the range of bass frequencies being distorted. The DS1 can be a very tinny, high end heavy pedal, so using mods that should open up the bass frequencies we should get a sound that is more like a cranked valve amp.

Firstly, letís take a look at what we are going to need:

Thereís a lot going on here, so Iíll highlight a few of the interesting changes and why I chose them:
R7 defines voltage bias and in turn controls the gain, higher values will increase gain, lower values decrease gain, but focus the low end. Iíve chosen to drop the value from 470k to 330k to tighten up the low end of the pedal.

Lowering the value of C3 will reduce bass end compression, Iíve elected to raise the value to 0.1uF.

R13 and C8 control which frequencies get clipped and distorted. I want to extend the distortion a little in the bass direction, but not too far. Lack of bass frequency distortion is what makes a lot of pedals sound empty and false. Iíve chosen to leave C8 alone, and Iíve reduced R13 to 1k.
If things are too fuzzy with this, then you can always raise R13 up to 2.2k

The clipping diodes are getting an overhaul too, replacing D4 for a bright blue LED which is extended through the chassis will not only give the distortion a more natural edge, but it will light up as a signal passes through the pedal. Itís a very cool look.

D5 is replaced by two 1N4001 diodes in series. These diode changes should provide a more natural sounding asymmetrical clipping.

The original tone control was very powerful and much of the range wasnít usable, so changing R17 and C11 can help create a more sensitive tone control over a smaller sweep for better fine tuning of the tones you are likely to use.

You can see the locations of all the changes highlighted on the circuit diagram and the pcb image here

(diagram borrowed from Brian Wampler, someone much more knowledgable than me with regards to effects pedals)

The modified pedal is exceptionally loud due to some capacitor changes surrounding the amplification stage and now plays very well with a clean valve amp, giving detailed and natural break up and low gain sounds.
Pushing the gain higher though and the pedal becomes very dirty indeed, aggressive and fuzzy. This could be very useful in come specialised situations.