[95] Fat mod for the Boss DS-1

Date: May 9th, 2008 | Comments : [64] | Categories: DIY.

Boss DS-1 mod

The AMZ 2-resistor mod for the Boss DS-1 Distortion pedal.

The DS-1 is a classic distortion pedal and is widely used by pros and amateurs alike. However, if it has any flaws, it is that the distortion is too extreme and the tone can be a bit harsh. This mod can fix both problems by merely changing two resistors.

The schematic at the top of this article is the input transistor gain stage in the DS-1, which is built around the Q2 bipolar transistor. It offers a lot of voltage gain and an extreme treble boost, which can make the distorted tone sound thin.

The two resistors that are changed in this mod will be R9, which controls gain, and then R6 to bring the bias back into the proper range. We want to decrease gain of the Q2 booster so the value of R9 is increased. Remove the 22 ohm original R9 and replace it with a 1k resistor. Next, take out R6 (100k) and put a 150k resistor in its place. That’s it!

I measured the collector voltage of Q2 after the mod and it was 4.72v, which is close to ideal. The lower gain of Q2 will give more control over the DS-1 boost, and will take it out of fuzz territory and solidly into the distortion range.

When R9 was increased, the input impedance also went up. This improves low end response and takes away some of the harshness. The drawing below illustrates the final configuration of the pedal after completing the mod.

If you don’t like the sound, the mod is easily reversed by replacing the original resistors. Give it a try and tell me how you like the improved fat DS-1 sound!

Boss DS-1 mod

The Boss DS-1 is currently selling for $39 in our online store. It is a great pedal whether you mod it or not!


64 Responses to “Fat mod for the Boss DS-1”

[3745] the heartbreakkid Says: 5:45 pm, January 30th, 2013

i would love to try this mod out to my ds-1 japan.(,”)

[3795] Ian Says: 11:25 am, March 10th, 2013

Hi. Daft question – would dropping the value of R7 (470K) also reduce the amount of gain from this stage?

(am eagerly awaiting my DS-1 in tomorrow’s post – many thanks for this article!)

[3799] Joao Says: 1:29 pm, March 11th, 2013

so i opened my ds1 up. i only got th transistors and the diodes identified on the pedals PCB.

[3810] Spectre Says: 3:44 pm, March 14th, 2013

@Joao–if you cannot identify components like resistor and capacitors, then you might want to have someone do the mod for you.
There are plenty of images on the Internet with the complete PCB and all parts identified.

[3860] Miegs45 Says: 6:37 am, April 28th, 2013

Excellent mod – soundds great ansd is easy to do. Was going to sell my DS-1, but now it stays on the pedalboard!

[3913] Fyl Says: 4:00 pm, June 25th, 2013

Anyone got a tried-n-true “MOAR CHUG” mod for DS1 (Taiwan)? Chug not fuzz, mind you…

I -kinda- like the description of this one, but with a few rather bassy guitars (Les Paul Custom w/ Super70s, Explorer w/ overwound PAFs, mahogany – yes mahogany not basswood – Ibanez superstrat w/ DiMarzios)… and into bassy amps no less, so I’m kinda afraid of making things even worse.

Amps used:
*Epiphone Valve Jr, always bypass internal speaker into Marshall 1960A 4×12 (veeeery bassy)
*Carvin ProBass 150 1×15″, sometimes w/ extension Marshall 1960A 4×12 (also kinda bassy, duh… less than the Epi, actually)
*Marshall Valvestate VS65 – shrill except at high volumes

*DS1 Taiwan (stock, candidate for modding)
*Aria ADT-1 Japan (Aria’s take on the TubeScreamer circuit, complete with the old JRC-4558 chip, but with a gain control reputed to “go to 11” – in comparison to TS)

What’s the verdict? Go or no go?

PS i rarely use the pedals past gain & level at 12 o’clock, and NEVER past 3 o’clock (also generally with the other control at 9 o’clock)

[3942] Ruben Says: 8:01 pm, July 29th, 2013

Love the mod cost me almost $.60 and about 20 minutes work turned it into a sweet Tone monster Thank you so very much Mr. Orman

[4171] Allan Says: 5:24 am, September 2nd, 2013

Wow! Now my DS-1 is usable. Thanks!!

[4206] Craig Says: 1:28 pm, September 12th, 2013

Hey, I thought I’d share my findings with this mod. I had already changed R16 to 4.7k to bring the mids back a bit, so when I did the fat mod I found that it had way too much bass. Changing C3 to 0.01uF made the EQ almost perfect for me. However, I had to roll the distortion up past noon to get any sort of distortion (even with humbuckers,) and I was getting a sort of police siren effect when the DS1 was placed after a wah. There was also significant hum. I changed R9 from the 1K in the mod to a 300R to give me a little more dirt, and it solved all of those issues. Gate voltage at Q2 is 3.95v. I’m not sure what the perfect voltage is for it, but it matches the Q2 gate voltage of my stock DS1. As I understand it, the FET has less headroom before distorting if it isn’t biased perfectly. Well, nothing wrong with that on a dirt pedal eh?

Thanks for posting this mod – it got me going in the right direction with modding this pedal. I’m pretty satisfied with it now.

[5598] First Act Distortion (MX-510) Mods | Texas Fuzz Says: 6:13 am, December 23rd, 2013

[…] resistors  which is Jack Orman’s “Fat Boost” mod everyone does on theoir DS-1.  Here is a follow up link to this specific mod for the Boss […]

[6310] BoX Says: 10:37 am, March 4th, 2014

dmc777, please send me all ds-1 mod schemaics you owned. I want to experiment with mone album mods. I will be greadful.

[6483] Artie Says: 10:11 am, April 8th, 2014

I just posted this simple mod that makes this mod switchable.


[95831] Lawrence Says: 10:00 am, July 17th, 2014

I love this mod. Is that a way to bump up the gain a bit without losing the overall tone of the pedal?

[753587] Bertrand Says: 7:41 am, October 28th, 2015

Hi !
I’ve just combined this mod and Brett Miller’s MIJ Mod on a post-94 DS-1 and the result is really cool.
A great and easy mod, thank you again for sharing it 🙂
Thumbs up !

Regards, Bertrand


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