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.

81 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 :)

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    1. Sure thing.

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

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  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!

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    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!

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  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?

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

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

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

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

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

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  5. i built it but doesnt seems to work properly

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

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

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

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    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)

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

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

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  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?

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  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?

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    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).

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

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  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 !

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  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 ?

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  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.

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  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...

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    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!

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  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....

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    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

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  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.

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

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

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  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??

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  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.

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  22. call it verified! works great

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

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

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  24. 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.

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

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  26. 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...

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    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 ;)

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    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?

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    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...

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  27. 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?

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

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    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).

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  30. 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!

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    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.

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  31. 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!

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

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  33. 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!!!

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  34. 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!

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  35. 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.

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  36. Thank you for the tipe, Dylan.

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  37. 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?

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  38. 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)

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  40. Can I attach a vc to this circuit?

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

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    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.

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  42. 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

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

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

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    2. Thank you for your help :)

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  45. 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

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

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    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

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  47. 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?

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