[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”

[431] admin Says: 9:52 am, May 14th, 2008

If this mod reduces the treble too much for your rig or taste, you can decrease the value of C3 to bring some of it back.

Start by changing C3 to 0.022uF or 0.01uF. The smaller the value, the more the low freqs will be rolled off.

regards, Jack

[436] David Says: 11:57 pm, May 16th, 2008

Very, very nice, and no, I wopn’t be changing it back. 🙂 Mr Orman, you’ve done it again! I also think this one tips the balance to having more changed components on my ds1 PCB than original!

[465] Erik Says: 12:42 pm, July 8th, 2008

Hi Jack. Thanks for sharing this mod. I just did this change last week and used my DS-1 on stage last Friday with pleasing results.

My DS-1 also has other mods done to it and C3 is 0.033uf right how. It’s a little dark so I’m going to try 0.022uf in there next.

I need to get another one and make just these changes for kicks.

[476] cornell Says: 4:55 pm, July 18th, 2008


[494] Harris Says: 3:20 pm, August 3rd, 2008

I have simulated the circuit in spice and this mod does not change the low-end frequency response. The frequency response becomes flat with a gain of approx. 8 between 100-10kHz which might give the impression of boosted low-end.

[555] Bozo Says: 2:37 pm, October 31st, 2008

I tried your mod and a peculiar thing happened. When I replace R6 with the new value the pedal produces no sound when the pedal is switched on.

Any idea what is going on? It works fine once I put the old resistor back in.

[557] admin Says: 6:10 am, November 3rd, 2008

Check the value of your new R6 resistor with a meter and make sure that it is 150k ohms.

Have you changed R9 as well? That is necessary.

Numerous people have successfully made this mod so it is definitely confirmed by modders other than me.

[572] fuzzo Says: 1:51 pm, December 3rd, 2008

I’ll try this mod tomorrow, but there’s a mod to give more mids to the pedal ?

[575] Maurica Says: 12:23 pm, December 12th, 2008

I was thinking about modding my DS-1 to make it good for bass guitar. Is this mod the deal? Have you tried this on bass guitar?

[624] Earthscum Says: 4:31 am, March 1st, 2009

Modded mine tonight, and used it at a show. I can confirm that it is awesome for bass guitar. I play an Ibanez gs205 through a Peavey TNT 115. Put my DS-1 in chain after my KMD Phaser aand with the tone straight up, volume about 1/4 up and dist cranked to about a 9, was able to bust out a sweet cover of Beastie Boys’ “Gratitude”.

This mod will cut your distirtion down quite a bit, but it is a raspier, meaner distortion. It also overdrives pretty niceley for a bluesy grumble. If you want full-on distortion, you can crank the dist all the way up, but I found my sweet spot for the night around 8.5-9. Gonna try a couple other mods though to try to get a bit of the distortion back. I play in a punk/alternative band, but I like my rig to sound metal. A bit more distortion back would be nice, just for that little bit of headroom.

BTW, the tone knob works sweet for the bass. You can tune it in along with the level and set it like a guitar, where you hear the bass still with the distortion added in a layer on top.

[636] Goran Says: 5:59 pm, March 23rd, 2009

I modded mine a few days ago. Sounds great!
Thanks Jack. I did many other changes to it
(caps, asymmetrical clipping) but this one
really cleans the sound.
I must say that the clone of DS1 I built from tonepad.com layout sounds still better with JRC4558!

[689] FEDERICO Says: 12:44 pm, April 26th, 2009

hi i´m new here, i ´ve been looking for the “hi Z input low Z output” issue that every body talks about… i read the pete cornish web page and he is got a point!
is that the reason why my DS1 is a tone sucker? not enough HI Z input? or what?

thanks for this forum!!! is great!

[783] joshua Says: 5:42 am, September 4th, 2009

Hi, how can in corporate this mod to the tonepad ds1?

the r6 100k in your schem is connected to the ground while the 100k is connected from the vb?

are they the same?

[852] Andreas Says: 4:53 pm, November 1st, 2009

Hi guys, I am new here and I will greatly appreciate your help on the following matter.

I did the Keeley SEM/Ultra-mode mod a couple of weeks ago and although I was initially happy with it, now I feel that:

1) the sound is quite distorted even when the distortion knob is at 0 (actually increasing gradually from 0 to 10 has a very small effect on distortion level, whereas from about 12 onwards distortion increase becomes more apparent)
2) The sound sounds compressed,…I don’t know if its the actual pedal or the fact that I have high output pups (or a combination of the two).

Anyway, what I wanted to ask you is that given that I have done the keeley mod, is there an additional change that I can do to correct those 2 things? i.e. the extreme distortion and the deeply compressed sound? I am asking this question because maybe Jack’s mod works as a charm provided that one hasn’t already changed anything else…and I have done a lot of changes already for the keeley mod..

Thank you

[859] max mejia Says: 9:17 pm, November 15th, 2009

Great Mod. I am a DS1 fan I did the Keeley mod, It helped but it compressed the tone a lot and ended up with squeeshy distortion. I think that this Mod by it self its a great deal.I would only change the Clipping diodes to LEDs and tame the tone control with a 10nf cap across the tone Pot. Cheers Fron Los Angeles

[863] Ricky Vinluan Says: 6:53 am, November 18th, 2009

If you’re into classic sound. This mod is for you. I tried this mod and to my ear my DS turnned like less gain “muff.” But this is a very good a idea. W/ some experiment you can add the principle on making the DS1 less fuzz. Great work Mr. Orman

[872] tadej Says: 3:43 pm, December 6th, 2009

hi! I will be happy if you replied me on this one. I did a keeley mod to a DS1 but didn’t replace the R39, R14 and R35 becaue I left a 3mm power led in it. the pedal works great but with 100% on the gain nob I would like to increase that for some 10-15% percent to make some room on it. should I replace R6 with a lower value like 50 or 60k?


[922] Tor Says: 9:16 am, January 22nd, 2010

any suggestions to where i can find the parts for this mod? i guess there are websites for ordering parts or local stores that sell them.

But is it possible to recycle parts from some old electronic equipment? like a pager, a busted up Rocktron Rampage amp or tv remote controlls?

[930] admin Says: 7:28 am, January 23rd, 2010

Try mouser.com or smallbearelec.com for the parts needed to build pedals or make mods

>>>any suggestions to where i can find the parts for this mod?<<<

[935] Catalin Says: 1:29 pm, January 26th, 2010


I tried the mod and I screwed up somehow. After I thought the two resistors were in place I connected the jacks and the only thing I got was an awful hiss and squeaks while I was touching the strings. I removed the resistors and it sounded the same, off or on.
Could it be possible that I shorted the circuit some place or broke it? In some place the thin conductive layer came off a bit but I think there is still contact there.
The good part is that I am receiving a radio station 🙂

[937] Catalin Says: 11:33 am, January 27th, 2010

Never mind, I did the test with all the guts out. I went to bed and then it hit me: the metal case is used for grounding. Now it sounds OK. Thanks!

[971] c.a.r. boy Says: 10:58 pm, March 11th, 2010

sweet sister mary….. 2 resistors….. 5 cents 20 minutes muckin` about….negotatable…..the sound…..priceless nice tip jack….you`re the man

[1018] Death metal Dave Says: 5:48 am, April 25th, 2010

Well nice to know the mods I use the ds1 and Hm2 for swedish death metal on the ds1 it makes this swrill sound don’t know why turn the gain down it goes awaybut will try some mods to perfect it its an old style but i still like the old analog stuff besides tube tone

[1063] Joel Says: 12:40 am, May 21st, 2010

Will this mod also work on the Super Feedbacker Distortion?

[1231] alfalfasprout69 Says: 4:41 am, June 25th, 2010

[1289] mrahogg Says: 4:09 pm, August 16th, 2010

Great mod, thanks for sharing! Just enough gain, when maxed, for bluesy leads on my strat with Kinman Woodstocks. But now the tone is smooth and chunky and still has the bite which I love the DS-1 for.

[1292] dmc777 Says: 11:15 am, August 24th, 2010

Hahaha! Damn alfalfa….how does it sound with all those resistor and cap improvements?

[1297] xfree Says: 2:37 pm, August 27th, 2010

I did this mod after buying another ds-1, I had a ds-1 before and had done the keeyley/brent mason mod and those @indyguitarist&premierguitar sites, and I wish I could have read this forum beforehand, which is better in my opinion.

The tone is more upfront with boosted presence & body, but the volume is compromised a bit, but overall it’s the best mod i have done to the ds-1. Yes the distortion is meanier! almost like a speaker-ripping like tone but still on the distortion color.the good point in this mod is that the clipping diodes are preserved and thats what i like about the stock ds1 .All you need is to bring up your presence and tone and this mod is the one we’re looking for!

thanks to the one who discovered this!
excellent contribution!

[1298] xfree Says: 12:51 pm, August 29th, 2010

for those who want back a little more gain, you can lower r6/r9 .I trimmed it to my taste and made R6(150k) to 120k and R9(1k) to 680ohms

now it sounds almost the same but is sweeter sounding this time

[1307] dmc777 Says: 5:31 pm, September 8th, 2010

I’ve been debating on which DS1 mod I’m going to do for a while. I used to have the Keeley one and liked it. I have the schematics for the keeley ultra seeing eye, the analogman “Super Mod” I think it’s called, and MonteAllums DS-1 Cmat Tri-Gain mod which involves adding a switch for led and diode clipping. I also have the single to dual opamps for monteallums. I think I may do this mod along with the tri-gain mod and a few part replacements on analogmans mod and see how that sounds. Then replace the single inline IC with dual Burr Browns. I’m really curious to hear this pedal with different Ic’s.

Xfree would you say this simple mod alone is better than the whole Keeley mod?

[1323] xfree Says: 12:27 pm, October 7th, 2010


I cannot say that this is better than the Keeyley for they were of different characteristic- If you love the stock ds-1 tone this is the mod for you.

[1330] Indio Says: 8:48 am, October 20th, 2010

Dear Jack

Thank You very much for sharing you know how with all of us.

Viva Jack

Saludos desde Lima – Peru

[2023] joplin66 Says: 4:36 am, January 11th, 2011

hi i did your mod successfully and i really like it but now im curious as to why this changed the sound and id like a break down of what parts on the ds1’s board affect what aspects of its sounf and how to adjust the tones. if i up the k’s will that mean more low or high end etc, how to make it louder, all that stuff. if anyone could help that would be great!

[2094] Harrisxr650 Says: 6:13 am, March 6th, 2011

Hey. just did this mod on my keeley modded ds-1 the tone quality i got from this mod is really great but distortion dropped a lot and i would love to have it back but with the same tone quality this mod gives:). anyone knows a trick on how to bring back the distortion

[2097] Steven Burvenich Says: 4:23 am, March 12th, 2011

Just drop R13 to 3.3k or 2.2k

[2100] Rafik Guergour Says: 9:28 am, March 14th, 2011

Salem alikum ! (Peace)
I have made a DIY DS-1, respected the values of the stock version except for the IC (no M5223 or NJM34.. aren’t available in my country) so I put an LM358N, when tone know passes 3, the sound is almost fuzzy .. and harsh .. I DO REALLY THING THAT THIS MOD IS THE CLUE !!
I’ll try it this evening with god’s will !!
How about C4 250p, does it have any influence on the choice of the IC??!

Thanks A lot Mr ORMAN !
Greeting from Algeria …
“.. True civilization is where every man gives to every other every right that he claims for himself”

[2106] Harrisxr650 Says: 7:56 am, March 19th, 2011

@Steven R13 was 2.4k from Keeley mod so i did some changes and ended with an 1k mf 1% resistor and sounds great for my taste. thanks anyway man 🙂
but i would like to ask now again :D…output is really high i set the level to 1 and less..any way to reduce output a bit? thanks again for the mod and the help 🙂

[2130] darbour Says: 2:07 pm, March 30th, 2011

I did this mod last night and the results are a little strange. I have a neck pickup that’s ~5k and a bridge that’s about 8.5k when I use the neck or the bridge on anything but near full volume I don’t get distortion but there is a strange high rasp. Like a really thin, quiet distortion doubling the guitar. With the volume up on the bridge it sounds pretty amazing, so I’d like to try and keep it. Any ideas? Help would be greatly appreciated!

[2195] thompsoneagle Says: 7:59 am, April 30th, 2011

First time modding and w/ success thanks for the tips. I wanted to make my ds-1 more suitable for bass. Think i like it so far but will try it out live tonight. Playing 5 string so the low b can be to muddy with some pedals and I want to maintain the great sustain I get from the bubinga wood!

[2207] DogFacedBoy Says: 11:03 pm, May 13th, 2011

Ok, I tried this tonight and it sounds pretty good. It’s not as loud, but still loud enough for some boost if needed.
I really like the tone knob now. I’m not sure if it’s got more bass or if the bass that is there is just not scooped or something, but it does sound fuller and more natural to me. The stock DS-1 to me sounds a bit like a wet fart into a tin can full of bees, but this mod makes it usable.

[2209] thompsoneagle Says: 2:17 pm, May 22nd, 2011

K i did this mod & loved i! Now i have played out with it several times with five & four string bass but do notice a bit of loss with pedal on….have to crank it a bit but think it could be squashing sound alittle….any suggestions, i used carbon comp reaisters?

[2216] Chris Gibson Says: 9:51 am, June 11th, 2011

Not sure if you guys are aware that this really sounds great and makes the pre 94 vintage circuit design with the toshiba ic sound amazing. It takes the ear piercing high hiss end of the distort right out of play. Most all info on the web is for the ds-1 with the grey ribbon connector non toshiba post 94 ds-1. This is the way most mods should be posted with a pic and circled parts. Schematics have too much variation.
Even the D2 is wired diff after 94. Plus it help to test all parts with a multimeter to get exact values. Heres a pic:



[2632] admin Says: 6:01 pm, February 8th, 2012

A simplified version of this mod would be to only change the R9 resistor from 22R to 1k. Leaving R6 with the original value will set the bias a little to high but it is not far enough off to be a problem.


[2652] sikter Says: 7:38 am, February 17th, 2012

Can you please tell me what L.E.D. is used in original boss DS-1.

I need a technical specification and part number.

The same question regarding for those two LEDs for boss LS-2

thank you

[2688] Brian Says: 1:13 pm, March 16th, 2012

You could replace R6 R9 with variable resitors and then one could adjust to his liking without having to change out for different values! Just a thought !

[2872] harris Says: 3:06 pm, May 1st, 2012

hey everyone. i wanted to ask again. is there anything i can do to get some more midrange freq? what resistors should i change or maybe use a pot to control it. thanks again

[3001] Fraser Says: 9:47 pm, July 3rd, 2012

Just put this mod in my DS-1 and I’m a big fan of it. Simple mod and the distortion sounds a lot better then before. Thanks for posting this!

[3678] Jeff Says: 10:23 pm, December 16th, 2012

I followed this mod and I did like it. I found a ds-1 laying around the practice room someone had left there years ago. Thought I’d try to improve it because after plugging into it…. well its useless as is. What I discovered personally that worked for me was doing this mod but also changing C3 and C2 to .022uf and R1 to 1k. Put it in front of a Ts-808 and its nice! I did actually run a straight wire in R9 later and then switched R6 to an unknown resistor but was blown away. The R6 is now gold orange purple yellow. Now stacked in front of the tube screamer is sets off a sweet smooth solo enhancement. Like the tube screamer knob goes to twenty.

[3711] Erik Says: 4:42 pm, December 27th, 2012

Just did the mod and I do like the sound better! In my opinion the ‘original’ DS-1 sounds a bit to plasticisch for my taste. That part of the sound is at first glance gone so that is a plus. The thing that surprised me is the non-lineair response the [Dist] knob now has. Up to 12 0’Clock not much happens but beyond that it enters a whole new world. Is that normal or did I screw something up?

At the moment it is all the way up (insert ‘to eleven joke’ here) but it is not to much gain. Especially compared to the added static noise my original DS-1 made when turning the knobs to extreme. I will play with it a little more tomorrow and will put my findings here again.

[3720] The Ultimate Boss DS-1 Mod | PDF Electronics Says: 1:11 pm, January 7th, 2013

[…] Resources: The Keeley DS-1 Mod DS-1 Building/Modifying AMZ DS-1 Mod […]

[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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