This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Friday, August 5, 2016

Korg MS-20 Filter

Switching it up this week and doing a Filter Friday. This one could be used for both synth and guitar/bass. It's a cool filter effect based around the LM13600/13700.

83 comments:

  1. by the way, do you have a schematic for it as a schematic and not a layout :) ?
    I want to make few pcbs of 4 of those on one pcb :)

    ReplyDelete
    Replies
    1. Sure thing.

      http://i756.photobucket.com/albums/xx206/storyboards27/Mobile%20Uploads/E9B94169-591E-4021-A7C4-D929F7F7BD6E_zpsdxarmfs2.jpeg

      Delete
    2. Point A for LFO...sounds interesting. What could that mean?

      Delete
  2. This looks like a great project! I've built a fair amount of pedals at this point but I've only done one perf build, and it was pretty messy. Can you point me in the direction of a good walkthrough about building on perf? I'm curious about the best way to make the connections on the underside of the board. Should I use wire, or try to bend the leads around, something else I haven't thought of? There are so many great projects on here, think it's about time I did some learnin' about perf. Thanks!

    ReplyDelete
    Replies
    1. I don't know of any good walkthroughs. Personally I bend the leads. I start with resistors and diodes, bend all the leads and solder accordingly. Then I populate the caps (smallest to largest), bend any leads and solder. Any connections left I make with cut offs. Good luck!

      Delete
    2. This comment has been removed by the author.

      Delete
  3. Thanks for that, it does help. I still have a few questions though. Do you solder the leads at bends or just where the components go through the board? Would you maybe be willing to post a few pictures of the front and back of one of your builds so I could get a visual idea of how things look?

    ReplyDelete
    Replies
    1. I solder them at the holes they come through as well as where leads join together.

      https://postimg.org/image/z32yj2chh/

      Delete
    2. Thanks!! Sets some ideas straight in my head.

      Delete
  4. isn't there a way to have a cv input?

    ReplyDelete
    Replies
    1. Yeah! It would be awesome to have CV input on this filter.

      Delete
  5. i built it but doesnt seems to work properly

    ReplyDelete
    Replies
    1. i also built it, used LM13700 and have some heavy noise and feedback, i can only use a 50% of each pot

      Delete
  6. In the PCB layout DPDT switch connections are wrong. Check the schematic to correct them and it will work fine.

    ReplyDelete
    Replies
    1. Could you be more specific in how to correct the errors? Thanks!

      Delete
    2. I could be wrong on this but given the numbering convention SW2 (IC Input) SW5 (IC Output) SW 1/6 (sig input) SW4 (GND) SW3(Vref)

      Delete
  7. will this circuit work on 3.3v/ 5v?

    ReplyDelete
  8. output should be on volume pin 2 no? pin 1 to gnd and 3 to signal?

    ReplyDelete
  9. I wanted to build a stereo version of this to warm up my digital synths, but I still read the tag "unverified" below this post. Such a pity... Has anyone finished it?

    ReplyDelete
  10. From reading the schematic; shouldn't lugs 2 and 3 of the volume be the other way around with lug 2 being the output like in most conventional layouts?

    ReplyDelete
    Replies
    1. Yes, but it works the same when you reverse those lugs. It's just the lesser used convention (tho DBA uses it all the time).

      Delete
  11. I hope someone verifies this one eventually, it sounds cool

    ReplyDelete
  12. I Think you can now tag it verified, mine seems to work properly, however with a few strange behaviour. When Reson pot is turned fully CW it produces a loud "mic-feedback" sound ; when Freq pot is turned fully CCW it totally cuts the sound.
    I don't know exactly how to use this with my bass :o) but I'm sure I 'll figure out !
    I use a LM13600 and wired the switch exactly like described on the layout.
    I'll try to debug the pots issues adding some resistors in paralell here and there and will come back to tell you more.
    And many thanks for this blog and your great work !

    ReplyDelete
  13. UPDATE : I didnt' notice with the bass (Std Jazz bass) but with the guitar (humbucker pickups) the sound is distorted.
    Perhaps this filter is not intented to be used with a guitar or a bass ?

    ReplyDelete
  14. And it is the same with both LM13600 and LM13700...
    Should I add a resistor in series at the input, or increase the value of another one already on the board ? If an expert has the answer...
    I also tried with my mixer headphone output : a lot less distorted at reasonable volume. But the sound is still pretty lo-fi and the pot's strange behaviour increased.
    Well, probably not verified yet. A DIY stompboxes guru should find a way to make it work properly.

    ReplyDelete
  15. OK, this is my last comment. I promise !
    I added a 47k resistor in series at the input : no more distorted sound !
    I then add a 10k resistor in serie at Reson pot's leg 3 and a 1k in serie at Freq pot's leg 3 : no more loud "mic-feedback" sound when Reson pot si turnde fully CW !
    I guess these pots don't act exactly as they should but it does work that way.
    You can use these values as a starting point to experiment...

    ReplyDelete
    Replies
    1. Hey I've had the same problem and couldn't figure it out. The 10k and 1k resistors goes in series with what? Each mentioned pot? Like solder a resistor in lug 1 and 3?

      Sorry for my english and thank you very much for posting!

      Delete
  16. OK getting ready to build this - Think I understand correctly - watched the video and there are 2 switches. One for Bypass (On/Off) - and One for HP/LP.

    The switch in the layout is the HP/LP switch - you would wire a second DPDT (or 3PDT w/ led) to act as the Bypass switch for On/Off. The instrument input jack runs to the On/Off bypass switch - and the input signal from there goes to 3 and 4 of the HP/LP switch (feeding input into the pcb board). The "output" label on the pcb gets routed back to the bypass DPDT to the output jack for the amp....

    ReplyDelete
    Replies
    1. Yup - got it
      https://youtu.be/XBZa-9Mc3lE

      Last question - should the lights be wired to the switch? - 1 for LP 1 for HP? They both light up at the same time right now

      Delete
  17. This filter from Korg MS-20 Synthesizer has unique sound BECAUSE it have mic-feedback in fully resonance pot. You don't need to put there a resistor - that will kill that unique sound.
    Sorry for bad English.

    ReplyDelete
  18. Verified PCB Layout:
    https://youtu.be/XBZa-9Mc3lE

    ReplyDelete
  19. Hey, does anyone have a vero version of this one ? Thanks!

    ReplyDelete
  20. Hello, i've build it, but i have no signal after 100k Resistor after the 100nf input caps.. i change the resistor, but after that it's the same...no sound...!
    any idea??

    ReplyDelete
  21. I finished building this last night, as far as I can tell it works properly. As others have said max resonate oscillates but that is common with ms-20 filters. Turning down the freq, cuts the signal completely, but that can be solved by adding a resistor in series. I'd say its verified.

    ReplyDelete
  22. its work fine with the IC LM13700 ? , i cant find the LM13600 ... and im very interested in this filter....

    ReplyDelete
    Replies
    1. ok i will try whit this IC and after will post my experience thanks very much

      Delete
  23. Hello! I've built this project and it doesn't work as a filter, it just oscillates. I'm using the LM13700. Any ideas on what could go wrong? Thanks again for all the layouts. Would love to see more synth projects here.

    ReplyDelete
  24. Do you have a new link to the schematics? The link on the comment further up doesnt work.

    ReplyDelete
  25. Just finished building it and it works!
    I built it in a volume pedal enclosure that i had, so I can use it like a weird wah pedal.
    Regarding the oscillation and distortion, it's part of the sound. Personally i think filters without oscillation are boring.
    Now I kind of wish to know how to add CV in...

    ReplyDelete
    Replies
    1. refer to this build of the circuit to add CV. seems pretty straight forward. You can hack into one of the legs of the res pot. https://www.lookmumnocomputer.com/projects/#/simple-filter/ So, the filter works well? I'm going to build one this week for my CZ101 ;)

      Delete
    2. So I'm looking at the build diagram for adding in the CV pot you posted above, but this circuit seems a bit different from the ms-20 filter circuit on this page. For example, he's got a couple extra transistors and a TL074 IC as well as all the attached resistors & capacitors. Adding this in doesn't seem straight forward, do you think a second board is required to add this control? Any other thoughts, have you built it with a CV input?

      Delete
    3. That's because the lmnc one is thought to be used with line level signals (synths). CV control would generally go to cut off freq (obviouslly you put it wherever you want...). Can put a vactrol in parallel with any pot you want to cv control...

      Delete
  26. Are the LEDs red, and are they for use as visual indicators, or are they being used for audio effects? In other words are they on the inside of the pedal, or mounted on the enclosure's exterior?

    ReplyDelete
  27. About CV input, is just a matter of adding a jack socket, or should I also add a 100K resistor somewhere ?

    ReplyDelete
    Replies
    1. It's not! You could use a vactrol or maybe some transistor cv control (look for the mods done to the mfos wsg on the mfos page, don't know of they would work with this one, could try breadbording them).

      Delete
  28. This comment has been removed by the author.

    ReplyDelete
  29. Sorry just a couple of brief questions, are the pots meant to be PCB mounted? Looking at the drilling template it seems that they are? In any case I bought solder lug pots. And are the LEDs shown on the pcb indicator lights? or are they part of the audio circuit?

    As always thanks so much for bringing these things to us, they're awesome!

    ReplyDelete
    Replies
    1. It's designed for board mounted pots, but you can use whatever you want. Or you can turn your solder lug pots into board mounted pots with a little bit of thick solid core wire or even some heavier cut offs from capacitors or diodes.

      The LEDs are part of the audio circuit. Not sure if they actually light up or not in this.

      Delete
  30. The build diagram says "In to Sw 3 and 4". Does that mean that the Input jack tip connects to Sw 3 & 4 separately, or does the input tip go to Sw 3 and then Sw 3 also connects to Sw 4?

    Thanks!

    ReplyDelete
  31. Sorry for all the questions but figured it out, verified! Thanks again

    ReplyDelete
  32. just finished, I used the LM13700, it works except for the leds (can't understand why), anyway it sounds very cool, just a little bit distorted (I also put a 47k resistance on the input) and I can't open at max the frequency pot (it cuts everything and produces only noise). I'll build another one with LM13600, thank you so much!!!

    ReplyDelete
  33. I built it with lm13600 and 13700 (also with 47k res at the input), I like it so much but the real problem is that I can't open the frequency pot at max and have the input unfiltered with the pedal on:
    At 3/4 of the knob suddenly it produces only a noise, can you please help me with that?
    Thank you so much, your work is great!

    ReplyDelete
  34. Quick update: I've rehoused it in a more common pedal enclosure, because with all that work on perfboard it deserved it. Then I made an expression pedal with the old volume pedal enclosure, and used it to control the frequency because I added an expression Jack! Just refer to the schematic above, use a switching jack between the frequency pot and the 100k resistors, so that the expression pot is in series to the wiper of the frequency pot. This way you can control the frequency with both. It may work as CV in too, still have to try. I also added a 4,7k resistor between the frequency pot and ground, that helps with the sound cutting off when counterclockwise.

    ReplyDelete
  35. Thank you for the tipe, Dylan.

    ReplyDelete
  36. are you sure the wiring on the switch is ok? because it seems that i get sound out when sw5 is connected but if sw6 is its just really really really quiet?

    ReplyDelete
  37. The LEDs on the board itself light up when the filter frequency knob is in use/open. When the filter is 'shut down' so lowest frequency the LEDs turn off. Remodelled two of these in series & parallel into a 500 series layout, so can get double LP or HP (for sharper slopes), or when in parallel can create a wide 'notch' or other alternative filter shapes using just LP & HP when serial or parallel signal modes. Works pretty nice, will compare against MS20 VST (got that too as an effect so could be quite cool to compare see how close this/Korg VST gets to each other)

    ReplyDelete
  38. This comment has been removed by the author.

    ReplyDelete
  39. Can I attach a vc to this circuit?

    ReplyDelete
  40. "VC" ? What is it ? Voltage Control ? If so, yes, afaik.

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. Yep, Voltage Control, although in this diagram I don’t see the input, just the output. I found an example about how to add the input or cv?. https://www.synthforum.nl/filedata/fetch?id=3113094 I’m not sure if that conection is output or VC.

      Delete
  41. You may look here : https://www.lookmumnocomputer.com/projects/#/simple-filter
    or here : http://guitar-fx-layouts.42897.x6.nabble.com/Korg-MS20-LP-HP-Filter-td31433.html

    ReplyDelete
  42. This comment has been removed by the author.

    ReplyDelete
  43. Can I buy LM13600N/LM13700N? Does the "N" at the end matter? I can't seem to find any LM13600/LM13700

    ReplyDelete
    Replies
    1. The N is just a manufacturers marking. Those should be fine.

      Delete
    2. Thank you for your help :)

      Delete
  44. If anyone is looking for a stripboard/vero version of this circuit, I sat down and “translated” it over the other day. It was my first time ever attempting to use the layout design software. I tweaked the layout a tad bit to make the wiring of the dpdt hp/LP switch match the schematics exactly and after I finished with the layout I built it to make sure it worked. I was able to verify that it did indeed work! im sure more experienced heads out there will probably see a more efficient way to make the connections. However, at this point in my journey I was just happy that I got it to work! 😆
    Enjoy!

    https://www.dropbox.com/s/tmql17e62dtxzx4/Korg%20MS20%20Filter%20%28stripboard%20adaptation%29.jpg?dl=0

    ReplyDelete
  45. Can anyone help and post the correct DPDT switch wiring for PCB layout at the top? Thank you in advance.

    ReplyDelete
    Replies
    1. I couldn’t get it working for the longest time until I realized there was a schematic for it...I’m sure once you see it, there will be no question how the switch is wired up. Here’s a download link. Just gonna leave it in my dropbox probably forever until the end of time.

      https://www.dropbox.com/s/74rt7ssxlfto2ow/Filter%20schematic.jpg?dl=0

      Delete
  46. I've tried building this twice and neither version has any sound output when engaged. Anyone else have this problem? Is it the DPDT wiring people have mentioned? Anything else I should check?

    ReplyDelete
  47. Probably not going to be helpful to post this but - I built this and while I get sound and the knobs all do things, it doesn't sound like I expected. The low pass has a sort of overdriven sound. The sound does cut off when one of the knobs is turned all the way to one side but I can't remember which now. In general it also seems quiet but that could be my imagination.. Went over it 3 or 4 times, cleaning it off and running my iron around. Double checked all the traces for bridges. Just sounds off. I used the etched pcb version btw.

    Hopefully this part helps someone! For people trying to figure out how to wire the switch - the lugs are numbered starting over at the top. When the input goes to 3 and 4 the wire from the input goes to the bottom lug on one side (3) and then the top lug on the other(4). It is just one wire, you could strip it back further to reach both lugs or use a little component leg to jump the,. Just make sure it doesn't touch anything it isn't supposed to!

    ReplyDelete