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Boss DS-1 Mods
by Brian Wampler
If you’ve been in a music store anytime since 1978, you’ve no doubt seen the ubiquitous orange Boss DS-1 Distortion pedal. Universally recognized as a good, inexpensive distortion pedal, you’ve probably even owned one or two in the past. Although it houses a simple circuit design, it produces a very good sound, particularly for a mass produced pedal. Let’s look a little more closely at the circuit and check out some changes that are available to make this great pedal even better.
Click to download a full-size PDF of the schematic.
The circuit is a buffered bypass circuit with electronic switching, as are all Boss pedals. The circuit comes in through R1, a 1K resistor, and then travels through C1, a .047 microfarad, or ìF, capacitor into the first buffer. This buffer goes out through C2 and then into a JFET (junction gate field-effect transistor), which is part of the switching. If the pedal is off, the signal goes out to the switching circuit and through the output through Q7, which is the other JFET. These JFETs act as a switch, allowing the signal to either go through the distortion circuit or out through the buffers, producing a clean signal.
When the pedal is on, signal travels to Q6, through C3 and into a transistor gain stage. R7 controls the gain of this circuit by changing the voltage bias, consisting of a 470k resistor which you can increase or decrease in value to adjust gain before the next stage. Increasing the value increases gain, while decreasing it will give you a little less gain overall but will tighten up the DS-1’s low-end response, ridding it of the flubbiness many people dislike. We can also decrease C3 to get this same effect by not allowing as much bass to come through. I like to change its value to either .022ìF or .033ìF if I’m looking for a less flubby tone. To clarify, to me “flubby” means a deeply compressed tonality. C4, which has a value of 250 picofarads (pF) also filters out some highs. Changing this won’t do too much, although you may be able to coax a little more brightness by changing it to a 100 pF capacitor.
The signal then goes out through C5 into the opamp. This opamp is used in a unique way to clip the signal. R11 controls the gain in combination with the distortion knob, R13 and C8. The gain control is set up this way to enable the clipping of higher frequencies as you turn the distortion up. When it’s turned down, it allows lower frequencies in – giving it a muddy sound since the signal is clipped beforehand through the transistor gain circuits, then clipped again when the distortion control is turned down. The first stage clipping is still occurring and as a result, the pedal doesn’t sound as clear and articulate as many would like. R13 and C8 are part of this “non-inverting” opamp circuit which provides negative feedback to ground. This is important for several reasons. The resistor value of R13 and the capacitor value of C8 basically provide a frequency range where the signal is made to clip. In this case all frequencies above 33hz is being clipped. To contrast, a Tubescreamer only lets frequencies above 728hz clip. This means that none of the lower bass frequencies are being boosted and/or clipped in the Tubescreamer.
 The signal goes out through R14, which is a 2.2k resistor, through C9, which is a .47ìF capacitor running across two diodes – D4 and D5 – and then to ground. All the usual diode tricks can be done here to allow more asymmetric clipping or different clipping flavors. Here C10 is also in parallel with D4 and D5 and is used to filter out highs in conjunction with R14. R14 and C10 form a low pass filter, cutting out high frequencies.
Go to indyguitarist.com/filter.htm and scroll to the bottom. Plug these values into the corresponding fields to determine which frequencies are being filtered. With the current values you will find it’s filtering everything above 7k, which helps to smooth things out a little bit. If it’s too bright, replace R14 with a resistor valued at 3.3k, allowing more highs to be filtered out, or try a 4.7k resistor to filter out everything above 3.3kHz.
After traveling through the diodes and the capacitor, the signal goes through a Big Muff ð inspired tone control. There are many things we can do to manipulate the tone here, and a great resource is the Duncan Tone Stack calculator, available at duncanamps. com/tsc/. Experiment with different values to find the tone you’re looking for. In the stock version of the pedal, the tone is a bit “scooped” meaning that there is little mid frequencies allowed through making the tone a little “thin” sounding. We can change that quite easily however. Check out the suggested changes in the charts below to get a warmer tone, a scooped mid tone or simply less highs.
After the tone control the signal travels through the level control and then out through R18, which is a 10k resistor, and then on to Q7, which is the other side of the JFET switching circuit. In its on state, it goes past Q7, through C13 – which is a .047ìF capacitor – through yet another output buffer and then a resistor, a capacitor and finally through the output.
Let’s look at some modifications that will have your DS-1 doing your bidding in no time.
Classic JCM-type Marshall Tones:
| LOCATION |
CHANGE TO: |
| C3 |
.033 |
| R17 |
15k |
| C2 |
1µF |
| D4 |
1N4148 Connected in Series to another 1N4148 |
| D5 |
1N4001 Connected in Series to another 1N4001 |
| C5, C9 |
1UF |
| R13 |
OPTIONAL - Change to 1k for tons of gain, if you do this, also change c8 to 1µF |
Modern distortion tones
| LOCATION |
CHANGE TO: |
| R16 |
1k |
| R14 |
10k |
| C10 |
.001µF |
| C5, C9 |
3.3k |
| D4 |
LED |
Vintage distortion tones
| LOCATION |
CHANGE TO: |
| D5 |
LED |
| C3 |
.033µF |
| R16 |
1k |
| C11 |
.001µF |
If you like the general sound of the DS-1 but are looking less highs and more of a tonal range change C10 to a capacitor with a larger value. Stock is .01ìF for a frequency roll-off of 7.2kHz.
Less shrill highs
| LOCATION |
CHANGE TO: |
FREQUENCY ROLLOFF: |
| C10 |
.015µF |
48kHz |
| C10 |
.022µF |
3.2kHz |
| C10 |
.027µF |
2.6kHz |
| C10 |
.033µF |
2.1kHz |
| C10 |
.047µF |
1.5kHz |
All in all, the Boss DS-1 Distortion is an inexpensive pedal that can rival many of the best boutique pedals simply by changing the circuitry a little. While this may seem difficult, technical and out of reach it really is very simple if you know what to change and where to change it. I hope that I’ve given you the knowledge and courage necessary to change your pedal from a mouse into a monster. Happy soldering!
Brian Wampler
Brian Wampler is an author, effects designer/builder and operates IndyGuitarist Custom Effects - IndyGuitarist.com and Wamplerpedals.com. His books include How to Build Effect Pedals, How to Modify Effect Pedals, and Advanced DIY Effect Pedals available at GuitarTone.net.
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Comments, Rants and Raves
Jorge Bolanos-Shaw on 2/13/2008 11:25:00 AM
Amazing discription!!!! thanks a lot...The best way to understand the way the signal travels and how you can mod it to your liking...
yontana on 3/2/2008 11:56:00 AM
Modern distortion tones C5,C9 change to 3.3k resistor really?
Milky B on 3/4/2008 9:52:00 PM
R16 is on the schem twice
jamie on 4/15/2008 1:51:00 AM
Is anyone answering questions about the C5,C9 to 3.3k resistor? Is this an error or is this an actual part of this mod?
brian on 4/20/2008 8:00:00 PM
c5/c9 in the modern mod should be r16... sorry about the typo
Thanks,
Brian
http://www.indyguitarist.com/
don on 4/21/2008 9:15:00 PM
Check me if I missed something, but 'r16' is already listed in the parts list of the Modern mod.
Also, on the 'Less shrill highs' mod, c10=.015µF=4.8KHz
By the way, you are the man Brian and thanks for the corrections. Your little article has really opened up my eyes to modding pedals.
Virgilio on 4/22/2008 7:43:00 AM
Great article. Great mods. Have tried a coupel myself with GREAT results. Thanks, Brian.
Ricabb7 on 4/22/2008 11:25:00 AM
Hello guys! I'm one of Brian's customers. I'm also a local pedal modder in the Phils. Anyway, I'm still wanting to hear the DS1 to have a tubey sweeter tone. More than just a crunch. So I'm still experimenting on the DS1 to achieve my desire sound. I'm pursuing to get Steve Lukather's gain distortion in DS1. Anyway you can check my DS1 mod work in this link. Just don't mind the playing because with such limited time I wanted to demo the DS1's capability after the mod. Tnx!=)
http://www.soundclick.com/bands/default.cfm?bandid=819476
Enzo on 4/22/2008 1:50:00 PM
Thanks Brian, great article ! A few days ago, surfin the web i find this: http://www.geocities.com/overdrivespider/DS1/keeleyds1.htm
Tell us what is you're impression about this.
nn buzz /Wilbert w. on 4/22/2008 4:13:00 PM
Brian i herd u on the radio. very good .and yes i like all of your ENFO. thanks Buzz
Nerd on 4/22/2008 7:51:00 PM
The R16 just left of Q7 on the schematic should read R18.
Nerd on 4/22/2008 7:57:00 PM
As don has noted above, after brian's correction of c5/c9 to r16 (modern mod) we now have two r16's in the list! Brian?
Lipi on 4/23/2008 5:45:00 AM
Thanks Brian!
I have already modded a DS1 a year ago but I did not like it's tone.
Your article will help me to make it sound better!
Jamie on 4/23/2008 8:54:00 PM
Enzo, while you are waiting for Brians response I would like to share my experience with those mods. I may have done something wrong with the LED's but in order to get the ASE to work I had to use the D-5 LED mounted in the case and not D-4. For whatever reason D-4 doesn't light up at all. I'm pretty psitive that it is hooked up right but,I could be wrong or have a bad LED. Either way I'm not too thrilled with the mod and added a 470 cap @ C-4 and it's twice as loud as stock (I keep a stock DS-1 for reference)power chords and individual notes sound pretty good but, if you try to play tripplets it sounds like crap. I bought a "grip" of caps,resistors,LEDs,and I'll keep working on this one till I run out of places to run jumpers on the backside of the burned out board. I can only try the same location about five times before it falls apart. So far this has only happened twice.
Magnus on 4/24/2008 5:55:00 AM
um . .I just wonder how to change R11 for more gain in the op-amp gain stage?.. and what value does this have stock ??
Jamie on 4/24/2008 6:13:00 PM
Check this link for resistor values.
http://www.electronics-lab.com/articles/basics/theory/resistor_codes.htm Can't remember stock value.10k I think. Feel free to correct me. I'm just trying to figure this out like most of us.
Jamie on 4/25/2008 8:22:00 PM
This page shows some of the stock values
http://trujeque.com/parts_list.html
Jamie on 4/26/2008 11:15:00 AM
Figured out my LED in D-5 was reversed. It is pretty bone shattering at high vol. but, blows at bedroom level.
yontana on 4/29/2008 3:16:00 PM
By the way, someone please tell me. Modern distortion tones C5 and C9, which makes it good value? ...?µF
Michael on 5/13/2008 10:25:00 AM
Nice discribtion, can you possibly modify the mods (the boxes you made with different values for JCM, vintage etc) so the different typos are corrected - im getting a bit confused myself.
Also id like a specific way to make the tone control more usable (or is that the Less Shrill mod?).
Thanks again man, this is great stuff. I can also recommend trying out germanium diodes - they sound warmer and better to my ears.
Philip on 5/14/2008 12:38:00 PM
Brian, I did the "classis JCM" mod. "C5" and "C9" is that the same as what is required in "C2". I do know now that C5 and C9 require a non-polarized capacitor, as they are non-polarized in the original format; (I purchased polarized) or does this not matter? I do notice that when the pedal distortion is all the way on there is a hiss that is hard to get rid of. Also, I chamged C3 to a .047 instead of the .033; would this create any issues? Any help would be great!
Philip on 5/14/2008 8:02:00 PM
Well, per the tech at a local radio supply shop, he said... It's all figured out now. However, when I swithced out C3 to the spec .033uf over my .047uf that I had originally installed, the sound now isn't as 'over the top'. The hiss is gone, but the distortion output suffered - there is less now.
Can I possibly merge some mods from the "modern distortion" along with what I have done already?
ayo on 5/15/2008 3:45:00 PM
My question is. If I increase the value of r7 to 1m or 510k and keep r13 at 4.7k(stock) . what would be the effect? Am I right in guessing that the distortion will sound heavier yet a bit cleaner?
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