DIY: Boss DS-1 Distortion Jack-of-All Mods

These DS-1 mods are designed to turn a widely available, affordable, and reliable pedal that sounds bad in most contexts* into a jack-of-all-trades box of dirty boost, drive, and all-out distortion.  With as few as four or five component changes you can turn a $20 pedal into useful dirt that can flatter any guitar and amp combination.

* “Icepick” being the most common descriptor

If you just want some good-sounding mods, they’re at the top of each section in bold, followed by tech talk and other mod options are.  Each section’s mods sound good to me on their own and can be used independently, though I recommend doing the Q2 biasing, tone stack, and diode series resistance mods (R6, R9, C12, R17, D4) at a minimum.

Q2 biasing

Here’s where to find my minimum recommended mods on the DS-1 board

R6 – 68K

R9 – 680 ohms

Resistors R6 and R9 bias Q2, a transistor gain stage close to the input of the circuit.  The stock biasing (R6: 100K, R9: 22 ohms) sets the transistor’s voltage gain very high, higher than the power supply can feed, and so the stage has its own clipping and frequency response colored by the transistor.  Jack Orman’s Phat Mod addresses this as well and results in a darker, smoother, lower-gain sound to my ears.  I did some math for different R6 and R9 values you could use to tailor the gain range to your taste.

  • v Most gain/distortion
  • R6 100K (stock), R9 22 ohms (stock) – Just for reference, this is not a mod!
  • R6 47K, R9 22 ohms (stock) – Stock voltage gain with a more symmetric signal swing
  • R6 47K, R9 82 ohms
  • R6 56K, R9 390 ohms
  • R6 68K, R9 680 ohms
  • R6 150K, R9 1K – Jack’s Phat Mod, for reference
  • R6 82K, R9 1K – Voltage gain same as Jack’s Phat Mod, with a more symmetric signal swing.  In other words, very similar range of distortion as the Phat Mod but a flatter frequency response.  Very nearly clean at minimum Distortion settings with Epiphone humbuckers
  • ^ Least gain/distortion
Tone stack

C12 – 22nF + 6.8nF in parallel

R17 – 8.2K

So much of the DS-1’s sound, such as it is, comes from the Tone control.  It mixes between a low-pass filter (LPF – R16 & C12) and high-pass-filter (HPF – R17 & C11), and the stock filters remove a lot of midrange and low-mid frequencies.  Losing these frequencies is why a stock DS-1 often sounds terrible into amps that aren’t already compressing hard and/or in band contexts where those frequencies are needed to hold one’s place in the mix.

The stock filters have cutoffs of 234 Hz (LPF) and 1064 Hz (HPF); my recommendation gives you cutoffs of 813 Hz (LPF) and 883 Hz (HPF).  This yields a pretty flat frequency response with the Tone control at noon, and musically useable bass- or treble-emphasizing settings to either side.

Jack Orman’s filter calculator will help you roll your own tone stack, if you like.

A trick is to remove C12 or R17, eliminating its respective filter from the tone stack entirely.  This results in a loud, full, sound and a flat frequency response that you can blend with the other filter.  For humbuckers I’d remove C12 (flat response with Tone control full counter-clockwise; can bring in some treble as-needed).  For single coils, maybe R17 (flat response with Tone control full clockwise; can bring in some bass as-needed).

(Honestly, for a no-solder mod, simply removing C12 or R17 with a pair of cutting pliers would go a long way to improving the sound of a DS-1.  Calling this the “Gonzo” mod!)

For a midrange boost I like C12: 15nF (LPF cutoff 1561 Hz) and R17: 8.2K (same as above).  For a mid cut, similar to but not as extreme as the stock DS-1, I like C12: 47nF (498 Hz cutoff).

Almost shockingly (if you’ve ever tried to use one into a clean amp with headroom), the DS-1 can have a really great, musical Tone control with the right filter cutoffs.  I like the 20K pot much more here than a Big Muff’s 100K (which uses the same type of tone circuit).  A ton of what sounds bad to me about this pedal is in those filter cutoffs.

Various C12 values and/or bypassing C12 can be put on a toggle switch for a variety of sounds.  As you look down at the circuit board component side with the input on your right (i.e. as you’d typically use the pedal), wire the C12 hole nearest to the power jack (signal) to your toggle, and the various things on your toggle back to the other C12 hole (ground).

Clipping diodes

I don’t have a go-to recommendation for changing these diodes (D4 & D5); once the Q2 biasing and tone stack are modded, the stock diodes sound good.

Adding a small resistor (I like 330 ohms) in series with either one of the stock diodes sounds even better to me, smoothing out the distortion’s decay and adding a touch of clean blend-like clarity.  This limits the current that goes through that diode and makes the clipping asymmetric.

I also like asymmetric Schottky diode clipping for a scuzzier, touch-of-fuzz sound.  One BAT46 and one 1N5817 is my top choice.  This results in less output due to the lower clipping threshold of the Schottky diodes, but the pedal is still plenty loud.

Lifting the diodes entirely is dangerously loud; proceed with caution 8-o

This (D4 & D5) is a great place to install sockets and experiment until you find what you like, and/or put a couple of different sets of diodes on a toggle switch.

Optional tweaks

C10

C10 forms a low-pass filter with R14, with a stock cutoff frequency of 7238 Hz.  This may be perfectly fine for you; frequencies above here can be described as “presence,” “air,” or “transparency.”

You could reduce it to something like 6.8nF (LPF at around 10K) or 4.7nF (LPF around 15K, which is in the upper range of what humans can hear and won’t be reproduced by your amp anyway).  It’s probably worth keeping at least a small capacitor (4.7nF or smaller) in here for the sake of removing radio frequencies.

You could also increase it, of course, for more “darkness” or possibly “smoothness.”  Brian Wampler has a whole table about C10 in his Premier Guitar article about DS-1 mods.

R15

This series resistor affects the level of the HPF in the tone stack relative to the LPF, i.e. the range of the Tone control.  If turning the Tone control full clockwise (treble emphasis) isn’t bright enough for you, you can jumper R15.  Vice versa, if turning the Tone control full counter-clockwise isn’t dark enough, you can increase R15.  It’s a subtle difference but if you’ve done my standard mods, jumpering R15 helps to balance the sweep of the tone control.

R7

In tandem with Schottky diodes in D4 and D5, sometimes I like to change R7 to 1M.  This results in a more fuzz-like, spongy feel to the pick attack.

Probably do not bother modding, unless you’re a giant DS-1 nerd (in which case please comment!)…

C5 – I calculate the -3dB frequency of this coupling capacitor and its load as 73 Hz; plenty low enough for guitar.

C7 – I like the post-1994 stock 100pF value here for a slight extra presence over the MIJ 250pF value, given that my other mods reduce the gain and high, harsh harmonics that C7 controls by allowing highs through a feedback loop.

C8 & R13 – Both Brian Wampler and Brett Miller, in their excellent DS-1 mod resources online, have mentioned these components forming a HPF at 33 Hz (which is lower than what’s typically used for guitar pedals).  I think this is a mistake based on the Made In Japan C8 value of 1uF.  Probably don’t mod a pre-1994 MIJ DS-1; get a post-1994 pedal, which should have a stock C8 value of 0.47uF, which raises the HPF cutoff and should be fine stock.

C9 – I calculate the -3dB frequency of this coupling capacitor and its load as 91 Hz; probably low enough for guitar.  Maybe if you tune down and notice a loss of low end, change C9 to a 1uF capacitor.

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