Dienstag, 26. Juli 2011

MONOMOD #1 --- Controlling the drums decay

This is my first Monotribe modification. I added BD/SD Dacay potentiometers and SD Noise/HH switches.

BD and SD Decay can be set with 2K2 log potentiometers. It is very important to add a 300Ohm resistor to it, to avoid a continuous decay, that never stops!

HH and SD-Noise Decay are set by a two way switch that has no connection on middle position and a 5MOhm and 20MOhm on the outer positions. While the resistor value needs to be very high to get acceptable decay modifications, i decided to use switches. The switches have no connection when set to center position, so the original decay value is still available. With both outer positions of the switch shorter decay values are possible.

If you try it at home, don't blame me if you mess it up and your monotribe gets damaged.

When using log potentiometers you need to ensure that you use the correct side of the potentiometers for the BD/SD Dacays so that you have a wide control range where you can set the decay relatively precise.


  1. Hey, donyounsell modded monotribes

  2. I've not been thinking about it yet. So waht would you pay for it? It's a modified monotribe that has lost all of it's warranty.

  3. Well I'm buying a monotribe today.....could I pay you a hundred bucks and ship you mine? You can send me your modded one or mod mine

  4. so i'm from germany. Where are you from? Shipping might get a little expensive.

  5. hi, i live in seattle, wa. I just bought a monotribe, if I pay you 100 and I ship you mine can you do the mods? I know you are not thinking about it but I will pay overnight costs and prepay the return, let me know if your interested. elugovina@mac.com

  6. i will pay for the parts too. you have done a great job love the video.

  7. hi, so the problem is that I have very few time. And i talked to my girlfriend lately and she said, don't do that, cause your's is unique and if you modify another one it won't be any more. What shoudl I say? She's right. The other thing is that you could do it by yourself. It's fun and afterwards you can say: "Hey, look, this is what I have done to my monotribe." :)

  8. hi, great job with the mod. i want to try this myself. I have 2 questions:

    1. where's a good place to buy the parts for this mod? I am also in Germany. A part list would be rally useful if you don't mind.
    2. Are you planning a mod to change the synth's octave on the fly? By this, I mean if the "octave" pot could switch the played octave of the recorded sequence (like the vertical slider on the MC 202)

  9. Hey Charles,

    i bought my parts from a local "Mükra" store in Karlsruhe. That's a nice choice, though the pots are quite expensive. I very nice place to buy music electronics stuff is definetely http://musikding.de/ The have all the parts you will need, very cheap and ship the stuff very quick. The parts list is very short for the decay mod. You need some wire, 2x 2,2kOhm Pots (log not lin!), 2x 300 Ohm, 2x 5 MegaOhm, 2x 20 MegaOhm resistors and 2x switches with on-off-on position (http://www.musikding.de/product_info.php/info/p391_Kippschalter-1polig-ON-OFF-ON.html). That should be it.

  10. for the second question. i don't plan this. so maybe you can find a way to do that :)

  11. ok thanks for the info, and that online shop looks just the thing I need.

  12. Great mod thanks! I will be attempting this over the weekend. Just one question, where do the ground wires solder to?

  13. You can see it on the first PCB picture. The wire soldered on the right side of the board is the ground. It's soldered to a bigger soldering point. This is what i used. You have also ground on the whole aluminum body of the monotribe, so you can use that too.

  14. Hi ed.klaus

    can you please tell which contacts of the pot are to be wired to what? From the schematics it looks like pin 2 to e.g. SD Decay and pin 3 GND.

    Thanks :)

  15. And a secend question right away: would it make any sense to try a pot with the SD Noise Decay?

    aka: Why did you use Resistors in the first place?
    best :)

  16. Hi,

    yeah that's exactly it. The Center Pin (Pin 2) to the SD Decay and Pin 1 or Pin 2 to Ground. Depends on witch side you want to increase/decrease the decay. Best is you try which way you like it most.

    Both Noise Decays (SD and HH) need very high resistance to get a hearable effect. If you find e.g. a 20M Pot you can use that for sure. I didn't find one, so I decided to use a switch, that enables me to choose between three different settings.

  17. Hi Ed, thanks for the help.

    Now I got it all up and running. Oonly thing is with BD and SN decay the interesting range only happens at the last 10% of the rotation way (cw)

    I used a 2k2A log pot and 300Ohm resistor.
    and I connected pin 2 to PCB Decay and pin 3 to GND.
    GND I took from the from the wire next to to the red wire of the connector that connets the synth PCB with the I/O PCB.

    Any idea on how to make expand this last 10% control range?

    Thanks a lot. :)

  18. I had exactly the same problem, when using a linear pot! So it's important you make sure it's a log pot you are using.

    Surely it's also important to have the 300Ohm resistor between the pot and ground.

    So when this is all set, I have no other idea, what could be wrong and how to expand the BD decay range. Sorry.

  19. Oh well, I just learned those clowns sold me the
    LIN type. Though then pots were labled "A"

    thanks again!

  20. You buy your electronics in a circus? :) Where did you get the stuff from? Need to avoid them :)

  21. Japan - that´s where I am currently (for the last few years, mostly) but next month I will return to good old Germany (Karlsruhe) to finish some stuff.

    Log Pots are rare in Japan and 2k log pots do not exist here.

    Can I use other pot value like 1K log of 5K log?
    some other schematics on Gearslutz even go as low as a 500ohm pot.

    cheers :)

  22. Oh that's funny. I'm living in Karlsruhe, Südstadt. :)

    So if you're here, drop me a note, maybe jam together, or drink some beers. :)

    You can use whatever log pots you like, but the control range will be different. I use 2K2 because 2K2+300 Ohms is the value where you get the original BD sound intended by Korg. If you use a lower value than 2K2 you will have an initial longer decay and can increase the decay when decreasing the pot from e.g. 1K to 0 Ohms. If you have e.g. a 5K pot you again will have a very small range of decay control!

    Another way would be to replace the 300 Ohms by a 1K resistor and use a 1K pot. You will have nice control of the decay, but the you won't get the max decay that would be available with 300 Ohms.


  23. For the help I already got from you I will def. invite to a few beers when I m back :)

    Maybe I will try a 1K Pot if I cannot find a 2K one next weekend.
    I already also tried a 1K Resistor with the 2K lin pot and this is just boring. 300Ohm Resistor rulez! The Bassdrum turns into a killer bass with the max decay And the Snare becomes almost self resonating. I totall love that. :D

  24. I sent you a message over soundcloud ;)

  25. sorry, but i still couldn't understand if there's a possibility to lenghten the decay of snare noise and hh, instead of just making it shorter.. you used resistors only to get them shorter!

  26. i did not find a way to lngthen sd noise decay and hh. sorry.

  27. hi ed.klaus. could you please post a link with the pot's you used from musikding? as a newbie to that soldering stuff, i have no clue which i should get...


  28. Wow, great work!

    Do you know what point I could tap into on the Monotribe to CV out the LFO? Amazing range on that LFO. Maybe there even is a point that could send CV out after the LFO amount so both knobs could shape the LFO CV being sent.

  29. hi, first i would like to thanks You for sharing You knowledge with Us. i do the BD SD HH mod & little more,but know i have a real problem : i touch a cable with ground to some place on Pcboard and my monotribe stuck - it turn's on,but then all red light are flashing(12345678),than flash green Flux,than Rec,than Play, than GateTime ,and the last red light (nr8) start blinking. Can You help me doctor ed.Klaus ?please heeelp. can i do a 'soft' reset on monotribe or smth ? i put a lot of work and money to this monotribe .... :(

    1. everything has back to normal !!! my MonoTribe live again!!! i remove the batteries and leave MT for about 2 hours. after that,it works again.sorry for my panic.it was horrible 2 hours ....

  30. Dieser Kommentar wurde vom Autor entfernt.

  31. hey klaus,

    thank you very much for your help and all your descriptions!
    i only fixed a midi kit to my monotribe but im going to do more.. first thing is the decay pots and switches like you did. now i ordered resistors at musikding but i didnt find the ones you said to use (didnt find 20 MOhm, 5 MOhm and 300 Ohm).
    is it possible to connect 3 resistors in series (7,5M + 7,5M + 5,1M)to reach the 20 MOhm?
    and.. would it be a problem to use 5,1M instead of 5M; and 330Ohm instead of 300 (i only found 270ohm or 330ohm).


  32. Hi,

    this shouldn't be a problem. You would maybe get some minor different results. But it shouldn't kill your monotribe. :)

  33. Dieser Kommentar wurde vom Autor entfernt.

  34. Hallo Klaus,

    hast du vielleicht Lust dein Tutorial auf http://www.machzin.de in Deutsch zu schreiben?

    Würde mich freuen was von dir zu hören (andreas[bei]machzin[punkt]de)

  35. Hey, I am just a little confused on the switches (I'm new to this whole business) What I am guessing is the SD noise decay and HH decay get wired to the centre pin on their switches, then pin one is connected to 20M, then ground, and pin three is 5M then ground? It doesn't make a lot of sense to me, I would really appreciate help with this.

  36. Hey,

    you need to take a 3-way switch. The center Pin of the switch is connected to the SD Deacay or to the HH Decay pin. One outer pin you connect to 5M, the other to 20M. In this way you have 3 Decay settings. When you switch to one of the outer positions the SD or HH Decay pin on the PCB is connected trough 5M or 20M to ground. And that's what changes the decay.

  37. Okay, I see. Thank you very much for the help!

  38. where do i put the wires onto the pot from which points? Can you take pic showuing where each wire is going/

  39. Hey mate thanks for your discussions here they are great, i was wondering ifyou think its possible to get a level selector for each waveform of the oscillator? rather than only selecting one at a time. making it more like sh-101 where it has a pulse level and a reverse saw,sub osc and noise fader. is it possible to just replace the WAVE switch with three sliders or pots?
    ALso have i was wondering if you think its possible to make the LFO and filter pots to be controlled by +/- 5V? Ie be compatible with moogerfoogers. i want to make this thing as modular as i can and having an RATE and INT, CUTOFF and PEAK 1/4' ins would be sweet.

    Thanks for your help mate

  40. Hey,

    that a quite nice idea to mix the waveforms together. I think it will be possible just to mix the three signals with pots.

    There ar some ways to replace a pot with CV Control. Best ways is to use a vactrol or a VCA. I never tried myself, but you'll find some advices here: http://www.midibox.org/dokuwiki/doku.php?id=midiboxfx_-_midifiying_analog_gear

  41. Hi there Ed,

    Thank you so much for all of this work and information that you have put into this wonderful little instrument. I am looking to mod my monotribe myself with this drum mod as I believe that the ability to change the drum sounds would be quite nice! I have done a bit of electrical work before so I believe I could do it myself, but I have a few questions. When wiring up the pots for the decay does it in a sense go in the middle of the path of the original wire, or how does that work? I know that you take a point off of the board, but then where does it reattach after the pot, other than the ground?

    I guess it is sort of the same question for the different lengths on the snare and hi-hat too. Where does the wire reconnect with the board after putting it through the three way switch, other than the ground? Does it reconnect at all? I notice in the picture that you have posted above that the blue wires look as though they just are all taped together at one end.

    I appreciate any help you could offer to me. I really would like to learn how to do this for not only the upgrades that it brings to the monotribe, but for the experience as well.

    Thank you,

    Hallo es Ed ,

    Vielen Dank für all diese Arbeit und Informationen, die Sie in diese wunderbare kleine Instrument gesetzt haben . Ich freue mich auf meine monotribe mich ändern mit dieser Trommel mod wie ich, dass die Fähigkeit, die Drum-Sounds zu ändern wäre ganz nett zu glauben! Ich habe ein bisschen von elektrischen Arbeit vor , so glaube ich, ich könnte es selbst tun , aber ich habe ein paar Fragen. Bei der Verdrahtung bis die Töpfe für den Zerfall es tut in gewissem Sinne gehen in der Mitte des Weges von der ursprünglichen Draht, oder wie funktioniert das? Ich weiß, dass Sie einen Punkt abnehmen der Platte , aber dann wo kommt es nach dem Topf wieder anzubringen , außer dem Boden?

    Ich denke, es ist eine Art die gleiche Frage für die unterschiedlichen Längen auf der Snare und hallo- Hut auch. Woher kommt der Draht mit dem Board verbinden nachdem er es durch den Drei-Wege- Schalter , außer dem Boden? Ist es überhaupt wieder ? Ich merke, in dem Bild , das du oben geschrieben , dass die blauen Adern , als ob sie gerade alle zusammen an einem Ende mit Klebeband zu suchen.

    Ich schätze jede Hilfe, die Sie mir anbieten könnte . Ich möchte lernen , wie man dies nicht nur für die Upgrades , die es bringt dem monotribe tun, aber für die Erfahrung.

    Vielen Dank,

  42. Hi,

    the basic cocept behind these mods is, that you modify the schematic by adding ground through a resistance to the schematic. So when the soldering points on the board are not connected at all, you have the default drums behaviour. But when you connect ground to these soldering points through a resistor, you get a modified behaviour of the drums voices. So it's as simple as connect one side of a resistor or pot (adjustable resistor) to the soldering points on the board, and the other side to ground. And you're done.

    1. Hi there, thank you so much for taking the time to reply, I really appreciate it! It is quite reassuring to hear that you just are adding a resister, variable or not, in between a point on the board and a ground. I have experience with soldering with guitars and such, but I have never modified any piece of analog gear. In fact my monotribe is my first foray into the analog world.

      So, now I understand that the resistor is going from the board to ground, but how does this affect the sound? I know you are changing its signal path and disrupting its flow, but how does a one way point to a ground point affect the sound? Do you know of any basic books or links that could explain this to me?

      Also, in the first picture above with the close up of the board there is a blue wire soldered to a big silver point on the board, what is this? As far as I can tell, all the other points are labeled so is this a ground point on the board itself?

      Do you think that it would be worthwhile to look for pots to control the snare and hihat decay or do the three way switches suffice?

      Thank you again for all the information and help, it is so kind of you.

      :) Austin