Finished Pieces


    The photo above shows two switches. One is illustrated below, the other is not very good, so I didn’t include it in the illustration.

    This page shows how to install a gated feedback effect. It’s a really great sounding effect. Sort of ringmod meets harmonic exciter of some sort.

    What is feedback?
    Basically feedback is where the audio signal from somewhere along the signal path is fed back into an amplifier stage somewhere EARLIER in the path. This creates a feedback tone and can result in some really nice sounding, rich tones when an incoming signal fights with the feedback tone.
    The problem with feedback
    is that when there is NO incoming audio signal, there is just steady, squealing tone.
    Gated Feedback is the solution
    I wanted to find a way to make the effect happen only when there was sound feeding into the pedal, so that when you aren’t playing into it, there’s no sound output.

    A transistor configured as a gate is the answer. I experimented with some transistors configured different ways and found the 2N3904 NPN to be the most effective.
    I encourage people to experiment with different types of transistors.

    In the drawing below, the yellow wires and purple and blue wires are the same mod! I photographed the circuit board after I had installed the mod switch. It’s impossible to see how the purple wires connect to the transistor and switch, so I drew yellow wires to illustrate how to wire everything. Ignore the purple and blue wires!

    – The distortion knob controls the effect.
    -I soldered the transistor to the component side of the board so that I could still close the back cover. The back cover presses right against the solder side of the board so there’s no room to add components.


    37 Responses to “BOSS DS-1”

    • 1

      joythief said:
      September 18th, 2009 at 2:17pm #

      hey! i am currently modifying and bending various FX pedals and was searching for what exactly you achieved, making the “bends” playable. however, i have doubts on how to hook up the transistor. sadly, my knowledge in electronics is basic at most and i am fairly new to bending and modifying, the bends i’ve found so far are due to the “connection” of two points in the board, but upon seeing your diagram i see that the middle pin of the transistor is making contact with a third point. should i connect this pin to a point within a path of one of the other points? can i connect it to just about any other point? does it make any difference?

    • 2

      casper said:
      September 18th, 2009 at 2:46pm #

      In the diagram you can see a yellow line coming from the center pin of the transistor. The yellow line connects the center pin to a point just left of the center of the board. Just follow the diagram:-)

    • 3

      jammastersticky said:
      October 7th, 2009 at 1:24pm #

      What a fantastic sound! As another just peeking into the world of mods and bends, this really is an inspiration. Thank you, Sticky

    • 4

      bosh dave said:
      October 16th, 2009 at 10:04am #

      was wondering whether you could use a trim pot rather than a transistor to offer just enough resistance to prevent constant feedback. also, is there much danger of me permanently destroying my ds-1 if i just start poking around trying bends? thanks

    • 5

      casper said:
      October 19th, 2009 at 6:24pm #

      I don’t think you’ll destroy your DS-1. My official answer is that anything is possible, so be careful and go slow.
      A trim pot won’t work. Adjusting the pot will change the pitch/depth of the feedback. That’s why I used the transistor. It adjusts the current flow between the feedback loop without varying the pitch.

    • 6

      Garrett Weeks said:
      November 30th, 2009 at 5:23pm #

      Hi I just wanted to say that I really admire this website and was wondering if you know of any books that have a good beginners guide to circuit bending and such. The reason is I am sixteen so I don’t have very much experience with tweaking electronic devices.

      Also I was wondering if you know of any mods for microkorgs? just wondering


    • 7

      Eli B. said:
      December 15th, 2009 at 4:50pm #

      Just a quick question before I start, I have the parts here, but in the diagram, the purple wires are from a separate mod, correct? I’m only soldering the four yellow wires shown? Thanks in advance!

    • 8

      Noise_ToyMan_BR said:
      January 11th, 2010 at 10:40am #

      man i’ve start bending 2 weeks ago and i maked a toy keyboard into a noise machine the toy have a potentiometer for regulating the pitch some switche to new drum machine like sounds and two adjustable (did i speak adjustable right? im brazilian sometimes my english fail hehe but not always) tractor and “alien cat” sounds and i plan more for this keyboard and for two quitars and a drum machine….
      please pete if you can recommend me some eletronics books or more content or sites like this i will thank you and i like alot your sound you rock man!!! 🙂
      greetings from brazil!!

    • 9

      J. said:
      February 10th, 2010 at 8:44pm #

      this looks easy enough, but as another person asked, are the blue and purple wires from another mod? can i achieve the sounds posted here by just doing the mod diagramed with the yellow wires? thanks in advance!

    • 10

      casper said:
      February 15th, 2010 at 3:52am #

      @Eli B- The Yellow wires and the purple are the same mod. I just re-drew the wiring so that it is more clear where to wire the switch.

      @Noise_ToyMan_BR. I would recommend anything by forrest Mimms. His book “getting started in electronics” is a good first electronics book.
      I’ve heard Nic Collins Hand Made Electronic Music book is really good too.

      @Garret. I would check out the books listed above. I’ve never worked on a micro Korg. I would advise against “bending” it unless you really know what you’re doing. The MicroKorg is a very cool and relatively inexpensive synth. I imagine they had to cut lots of corners to keep the price down. I imagine the construction and circuitry are fairly delicate. There may be some interesting bends or mods in there, but I bet it’s minimal.

    • 11

      casper said:
      February 16th, 2010 at 1:47am #

      @J- Please read the revised text for this page. The yellow and purple wires are for the same mod.

    • 12

      t-pain said:
      March 12th, 2010 at 10:43am #

      Hey, I did the mod like you showed it in the picture, however, the signal after engaging the pedal was at first very weak and then after I removed the transistor there was no sound at all after engaging the pedal. What could I have fried?

    • 13

      casper said:
      March 13th, 2010 at 11:38pm #

      @t-pain: Lots of people have done this mod and I haven’t heard of anyone encountering that problem. There are so many variables. It’s hard to say what exactly went wrong. I would check everything and make sure there aren’t any shorts (component leads touching each other)

    • 14

      t-pain said:
      March 15th, 2010 at 12:18pm #

      solved it, wasn’t any of the mod’s fault. I put the switch directly below the gain pot, and had to rotate the pot itself by 180 degrees, and aparrently the short remaining leads of the pot pierced through the insulation and touched the chasis and thusly shorting everything. Wasn’t really expected so I gave naturally blamed it on the first thing that came to mind, unfortunately that was this mod. Sorry, no hard feelings, eh?
      The mod sounds great, btw. I don’t know if this occurs with the stock version, but I also did the keeley mod and at higher gain settings it produces a sort of fluctuating-gated-tremolo effect. Awesome, if I may add. However, it seems that some of the bent signal passes through even with the switch off. Might be due to the keeley mod, not really sure. But I have another on it’s way and I do intend to do this mod again, however I’ll try a DPDT to cut out two leads of the transistor and see if it gets rid of the “leak”.


    • 15

      bmbr said:
      March 18th, 2010 at 3:54am #

      I don’t understand, it doesn’t work, the sound is the same when the switch is turned on or off. Could you help me please !!

    • 16

      casper said:
      April 11th, 2010 at 1:12pm #

      @T-pain: glad it works! no hard feelings 🙂
      I wonder if adding a resistor or two would limit the leaking signal… hmm

    • 17

      casper said:
      April 11th, 2010 at 1:14pm #

      @bmbr: it could be the switch, your wiring, the pedal, a short, a broken wire. I don’t know what to tell you. You need to eliminate your variables.. check everything and test as you go.

    • 18

      plasticaniml said:
      April 20th, 2010 at 3:48pm #

      Have you tried the SpeaknSpell keyboard mod to control the pitch of the feedback? I was thinking this could be fun to play with.

    • 19

      casper said:
      May 2nd, 2010 at 12:51am #

      that’s a great idea! and relatively easy yo implement. Send me pictures and samples when you finish it!!

    • 20

      what said:
      July 26th, 2010 at 2:02pm #

      Hi,I was wondering how you could find out the placement location of the transistor and switch on a different distortion pedal. Thanks

    • 21

      casper said:
      August 7th, 2010 at 9:23pm #

      @ what:
      This is specific to this pedal. I don’t know that this would work with any other pedal.

    • 22

      Evan said:
      August 9th, 2010 at 12:17am #

      Hi, I was probing around with a couple of jeweler’s screwdrivers before I just gave up and decided to use your mod, which sounds a lot better than anything I was able to find. I managed to fry the transistor in the Q1 position. Do you have any idea what value the transistor in question is? I tried looking this up, but I’m pretty bad at reading circuit diagrams. Thanks.

    • 23

      Kabum said:
      September 6th, 2010 at 7:52am #

      So this mod essentially turns your DS-1 into a fuzz factory

    • 24

      YYC155 said:
      January 27th, 2011 at 5:06am #

      It’s still not clear. You have 3 connections instead of 2, as in the “normal” feedback mods. How is the transistor wired? “Output” to base, “Input” to collector and emitter to ground? My DS-1 is a copy, so I can’t locate the connection points…

    • 25

      Beset by Apes said:
      March 12th, 2011 at 5:03pm #

      This is a great mod. I added a second switch and tried adding a capacitor, which smoothed out the sound a bit. When you use an Ebow on your guitar the pedal is amazing: all sorts of powerful effects can be gained by moving the Ebow over the pickups. Love it!

    • 26

      casper said:
      April 2nd, 2011 at 1:31pm #

      Happy to hear it worked for you!

    • 27

      Auxlo said:
      April 23rd, 2011 at 7:32pm #

      You said “I soldered the transistor to the component side of the board”. It would be sweet to show a pic of your success in this area.

    • 28

      Andy said:
      July 25th, 2011 at 3:36am #

      Hi – interesting Mod – would like to know are you using a standard two way toggle SPDT switch, also can the 2N3904 installment be bypassed via switch to a standard DS-1 or is the mod on all the time…

    • 29

      casper said:
      September 2nd, 2011 at 5:37pm #

      Using a regular ol’ SPDT switch. Yes the 2N3904 can be bypassed. that should be what the switch does.

    • 30

      Dylan said:
      December 23rd, 2011 at 1:31am #

      Installed this mod tonight, it sounds amazing! I wrote a little how to on it for my blog as well, and you can check that out here:

      I was just curious, what’s that other toggle switch?

    • 31

      casper said:
      December 23rd, 2011 at 1:25pm #

      Hey! thanks for the great How-To. I don’t even remember what the other switch did. I just know that I regretted installing it as soon as I finished.

    • 32

      kvnvk said:
      April 12th, 2012 at 7:55pm #

      just a quick question… the wiring appears to be the “synth fuzz with octave” mod, I wanted to know if the addition of the transistor affects the octave effect at all or if it simply gates the constant feedback tone? thanks.

    • 33

      Ian said:
      August 9th, 2012 at 8:17pm #

      Two issues – If I dime the distortion knob, should I still be getting a persistent feedback, or should it be gated all the way up the dial? Also, when I have the switch in the off position, the sound tone sounds stock, but it is feeding back constantly. could the transistor be bad?

    • 34

      Jbiz said:
      August 19th, 2012 at 4:51pm #

      Did the mod. Pedal does not turn on now or even allow audio thru. Did i fry something? Pretty new to soldering so maybe something like that

    • 35

      mikebike said:
      June 6th, 2013 at 2:50pm #

      do you think i could send the transistor gate CV?
      Id like to send it an LFO signal to trigger the gate.

      I was thinking i could hook one side of the switch to the middle yellow point in your picture, one to a CV jack, and the center to the middle pin on the transistor.

      I would like to send it the lfo from my sound lab, will there be an issue with sending a signal from the +/-12 circuit to the 9v pedal?

    • 36

      casper said:
      August 1st, 2013 at 4:26pm #

      @ MikeBike. Sending signals from a +-12 synth could cause problems with your 9volt pedal. but the transistor will function as a partial buffer. To be safe I would add a restor in series with your CV input. try a 1k…or a 10k. AND you could add a diode so the negative swing of the LFO wont effect the input…

    • 37

      marcan said:
      November 8th, 2013 at 3:55am #

      hi, mod is very good but there is a lot leaking signal and the bent signal passes through even with the switch off. You said, you add resistor it’s maybe better, i try 100k but doesn’t work…wich resistor do i need ? diodes 1N4148 is good for that ?
      if you add a idéa ? thanks much

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