Photo Journal of my Danik Shruthi build (Input pot increases resonance?!?!? WTF )
  • Hello everyone! I will be building a keyboard version of the Shruthi.
    I’ll keep this thread updated with pictures, plans and of course troubleshooting questions! Of course everyone is invited to chime in and post their ideas!

    My build will feature a Shruthi-1 Yellow Magic, full Shruthi Programmer Controls and a 3 Octave keyboard with Pitchbend, Modwheel and octave +/- buttons. I will salvage the keyboard and the controller from a 5 octave Behringer UMX controller which is going to be cut down to 3 octaves. The reason for this is that it’s still cheaper to destroy a perfectly working device that costs ~120Eur than buying a Doepfer 3-octave keyboard for DIY along with its controller which costs ~180Eur!) ( proof )

    Since it will have it’s own backpanel, I will not use the Shruthi-1’s MIDI and Audio jacks, I will solder cables instead and put them in the backpanel. I will also use a Mean Well 7.5V Switching PSU ( this one )

    The front and back panel are going to be made out of transparent plexiglass painted from the inside (resulting in a “piano black” look, or piano white for that matter). The side panels and the bottom and rest of the case are probably going to be made out of MDF, but I’m also thinking of making them plaxiglass, too. We’ll see about that.

    I have already ordered everything I need except the case. I’m currently waiting for the stuff to arrive and start soldering.

    For now, here is a draft of the panel layout:

    Full size image

    ...and a draft of the final build in sketchup (I’m really bad at this, the final will be much better!)

    Full size image

    panel texture.jpg
    5000 x 1588 - 365K
    Danik Shruthi.jpg
    1409 x 720 - 251K
  • Awesome! Seems like there’s a few folks planning keyboard versions. Looks like it will be a pretty one :)

    Building in the PSU is a nice touch, too.

  • That is similar to what I was planning so I’m looking forward to seeing what you come up with.


  • Very very nice! Look forward to reading this thread.

    I saw a similar one floating around a blog somewhere. Now this one will only add to that addictive need of wanting to make one.

  • Nice Shruthi-Keyboard :)

  • ItsDanik, two things that I’ve been considering for my next XT had to do with layout and finish. I decided to make the layout fit the way I would be fooling with the knobs in a live situation while playing, meaning anything I would change live would be accessible to the left hand while the right hand played the keyboard. So, my next XT layout will be the opposite of my first. The other thing is the finish. If you paint the underside of the plexi, the finish will be shiny, meaning it will look great in certain lighting situations but you may get alot of glare in other situations. You could get around this by spraying the top with a matte clearcoat perhaps.

  • Nice clean modern layout, beautiful.

    Does anyone know of a lead on good quality keyboards (other than Doepfer, which has a single dealer in the US)? Maybe Japanese? The Fatar Waterfall is my favorite action but I’m assuming they have some competition somewhere.

  • Thanks everyone for your input!

    Randy, I’m way too used to reading the synth panels left to right, top to bottom. I play a lot of basslines with my monosynths using my left hand, too, so I don’t think there will be any problems with that. My last mbsid was done in the traditional “LCD on the left, controls on the right” and I didn’t ever have any problems with it. Moreover, these are 3 octave keyboards so even if you’re playing right-handedly you can easily cross your left hand over and tweak the knobs without breaking any sweat!

    As for the finish, wouldn’t it be easier to achieve a matte effect by painting directly on the outside of the Plexiglas? I’m not sure I want to avoid a glossy look. I can even put stencils that way and leave a logo unpainted and illuminated by LEDs inside! I’m starting thinking I’ll do the rest of the casing out of wood, because it’s so much sturdier and easier to work with, though, leaving the top and back panel to shine Plexi-glory :)

    Greenrange, I’ve searched a lot about it, and I concluded the easiest and cheapest way is to salvage parts off a cheap MIDI controller for the keyboard.

  • As long as it works for you. I noticed my left getting in the way when I was tweaking and I couldn’t see the LCD so I’m going to try it backwards for the next one. I thought you were going to paint on the inside of the plexi. Glossy looks nice but I can’t think of any synths that have a glossy finish.

  • I know, that can be a pain in the ass, that’s why I put the LCD up there, no chance of it getting blocked by any hand! :)

    Most probably I WILL end up painting on the inside of the plexi to achieve a glossy look (like the Piano lustre). As for the synths, I am pretty sure all 3 Mutable Instruments synths’s original case design is glossy :) It is true, most commercial products go for professional look, and they want to keep them clean and easy to use (gloss = fingerprint collector). But at the end of the day, the iPhone is sexier than the Nord Lead :)

  • @ItsDanik – The iPhone’s pretty, but the Nord’s not exactly hard to look at. Redheads….. sigh.

    Thanks for the keyboard salvage tip, that’s very helpful.

  • Looks very pretty. Good luck with the build!
    I’m also building a keyboard version at the moment. Learning a lot and having fun. Maybe we can trade tips/ideas along the way…

  • Sure, I’m all open to tips and ideas and I hope I inspire other people in the process, too!

    For now, here’s a thought I stubled upon:

    The keyboard controller’s MIDI output is going to be wired directly to the MIDI input of the Shruthi. At first glance, this means I can’t have MIDI input in the back panel because two MIDI streams would bottleneck, right? I could always build a MIDIbox MIDIMerger (costs around 30eur including shipping), but I don’t feel like adding extra circuitry and wires.

    I could always “Y-cable” it to the back panel, too, though. My question is: As long as I don’t send anything simultaneously from both the integrated MIDI keyboard and the MIDI input, I should be OK? Or is there any constant data exchange? (MIDI clock?)

    Another thought is to add a simple physical 3PST toggle switch named “Local Control” which breaks the Keyboard connection, so I can use this whenever I need the MIDI input (mostly for firmware updates, probably). See Pic, I hope it is understandable:

    What do you think? Would the switch be important? Or would the Y-cabling work as long as I don’t send simultaneously?

  • Hi,
    i’m really looking forward for this journal. The sketches look great.

    Why don’t use a switch to switch between Keyboard-MIDI and externel-MIDI? This way there can’t be any mix-up.

  • Using a 3PDT switch, huh? That’s a good thought, too! :P

    Thanks! I’ll consider that! The reason I didn’t consider that in the first place, is I will rarely connect (if ever) anything in the MIDI IN of the shruthi. Maybe when I need to update the firmware, and that’s it :)

    Nonetheless, no harm done in having the switch…

  • Polychaining Shruthis is pretty cool so I would put the switch in just in case. I was going to be even more lazy. I figured if I’m going to use a donor keyboard that has a MIDI in and a MIDI out, I would run the MIDI ports from the donor and the Shruthi to the rear panel, and then just connect a short MIDI cable from the donor out to the Shruthi in manually around the back. No wiring and I can change MIDI connections very easily, although it’s certainly not very sophisticated.

  • That could work, too, although I’d be frustrated to know I have cut corners! But what you can do is actually hardwire the output of the MIDI keyboard to the input of the Shruthi internally, and configure the donor keyboard to forward anything on the input to the output (Thru-style), if the keyboard software allows it (most likely it will). This will work as a MIDI merger, too. Then you just wire the MIDI input of the keyboard and the Shruthi output (configured the same way) to the back panel, and you’re good to go!

    Unfortunately, my Behringer controller has only MIDI output, so, no go for me.

    As for polychaining Shruthis, I imagine it’s awesome, but an Ambika is on its way in some months :)

  • Sounds like you’re covered. I’m considering using an Alesis Micron as the donor and, at least at home, I will run the Shruthi and the Micron separately into a MIDI patchbay so having the ports on the outside works for me. I have three MIDI patchbays at home. At a gig, I’ll just hook up the single cable.

  • Here it is, my build’s first PCB :D
    I believe it’s self-explanatory

  • Progress has been made during the weekend :D
    Here we are, an introduction to the disassembled Behringer UMX Keyboard Controller:

    1) Motherboard:

    At first glance, one can say that the PCB is of very good quality (impressed!)

    It has 9VDC Input but it can also be powered from 3x AA batteries (4.5V) as well as USB (5V). I saw a 7805 regulator on it, so I guess if it handles 9V without a heatsing, the 7.5V my PSU pushes out will be just fine.

    I’m not going to rewire the footswitch jack to the back panel, since I think a sustain pedal is overkill for a monosynth (and I wouldn’t use a footswitch for anything else).

    The power switch is going to be always to the “ON” position (I’ll just switch the AC input and the PSU will power both the controller and the Shruthi at the same time).

    I’m going to solder 3 wires from the MIDI OUT to the white connector from the PCB in the picture in my previous post (above) which is going to be the MIDI OUT of the keyboard, which eventually is routed to the Shruthi MIDI IN.

    All these white headers are connections for the keyboard and some other peripheral PCBs which have sliders, pots, switches etc. These HAVE to be connected, otherwise the unconnected/floating shift register pins are going to pick up noise and we’ll have lots of random values transmitted over the CC# they control, which may or may not mess with the patches, but are going to create a lot of excess MIDI data traffic, anyway, which is never a good thing. I could try disabling them by the controller settings, I guess, but I’m afraid of a random memory loss/factory reset. I could also make a small pcb which shorts the inputs to the ground, but that would be time-consuming for no particular reason. I think just connecting them and let the rest on the bottom of the case is the easiest/best solution. Moving on…

    2) Pitch and Mod Wheels (unpainted yet):

    Not much to say here, just two pieces of plastic, pitch has a spring for resetting to the center position. They are connected to two pots, which are on tiny PCBs with 3 pin connectors on them. The cables are removable/replaceable! Behringer has gone out of their way to build an easy-to-service product! They could just solder the wires, but NO! They used connectors instead! Way to go, Behringer!

    3) “Pots and switches” board (that’s how I named it, anyway!)

    A typical “pots and switches” PCB which is just going to be connected and put under the keyboard (for reasons I have already explained).

    4) Control board (again, loosely named)

    This is the board that has a slider which by default sends CC#07 messages and controls MIDI volume, it has a set of octave +/- buttons along with their LED indications and two other buttons for configuring the controller and assigning controls to various pots and switches for the previously presented PCB. I only want to use the octave +/- buttons with their respective LEDs, so what I did is I desoldered the two switches and two LEDs and I made a small veroboard where I put them and soldered a 7-wire ribbon cable to the original board. This way I can save space on the panel surface where the Pitch/Mod Wheels reside and only have the veroboard above with the octave up/dn buttons and the LEDs. The rest of the board is going to be inaccessible at the bottom (volume slider maxed, of course :P)

    5) The Keyboard

    This thing is of the highest quality! I can’t believe they actually have a small weight inside each key, spring action, and a full metal underside! I always thought the feeling is nice on these keyboards (for their money), but seeing how they achieved it is a whole other matter! I had a small adventure, too when cutting the keyboard down to 3 octaves:

    The first part of the adventure is that the last C note (C6) would have to move from the end of the keyboard and replace the C4 (i used the first 3 octaves because the connectors to the motherboard are near the first key).
    This is not easily done because all white keys are different! the C4 has a small reccess for the C#4 to snug in. It would look ugly if the keyboard ended that way, so I needed to mod/cut stuff on the underside of the keyboard (where the keys mount) to make the C6 fit in there.

    The second part (far worse, btw) is that the controller reads keys in groups of 8 (they are multiplexed). When I cut the board, I was forced to scrape it to reveal the copper tracks and solder a wire on it to close the circuit (otherwise the last 5 keys wouldn’t work because they belong in the next group of 8, for which the circuit closes and backtracks after the place where the PCB had to be cut). This took a good 2 hours to figure out and achieve, but it is done now!!! Pretty happy with the result!

    I think that’s it for now!

  • Revisited (and probably finished) 3D model of the synth in SketchUp!

  • Thanks, it encouraged me to kill my Micron for keyboard and make “Shruthi-1 Kb”.

  • The Micron is a good candidate for donor. I had one and sold it, didn’t like the sound. Ttries too much to sound like analog in both the oscillator and filter section while none of them is analog. On the other hand, the Shruthi has digital oscillators which truly sound, well, digital (hence the wavetables), and analog filters which truly sound analog glory. A much more honest approach. So, I think killing a micron for a shruthi is probably a good choice.

    The only problem with salvaging parts rather than buy off-the-shelf parts is you never know what is under the hood or what you might run into in the proccess of retrofitting it to your needs…

  • I realized I haven’t calculated where the screws are placed on the PCB in relation to the panel. This is nowhere to be found on the Shruthi documentation, because the PCB is not mounted to the panel using screws. Can anyone help???

  • Just glue some 11mm spacers to the back of your Panel – no ugly screws.
    Otherwise the Files are in the GitHub repository, Top and Bottom match exactly, the holes are in the Bottom Panel.

  • Thanks for your reply!
    Will the glue withstand the button-pressing and knob tweaking of a lifetime?
    Didn’t know they were at the bottom and I kept searching for it! Thanks!

  • A last thing: you can use panel mount pots like the Alps RK09L1140A2U if yo want the pots to be screwed to the top panel.

  • And maybe panel mounted encoder to go with it.. i plan to use that one on my programmer

  • I was thinking of mounting the whole Shruthi PCB on the top panel along with its PCB encoder/buttons/LEDs/pots and use panel mounted pots for everything else (all programmer pots and volume pot)...

  • Id go for Panel mounted Pots/Encoder and put better buttons on a Perfboard PCB thats held with 5mm Spacers (or whatever fits your Panel). Either Glued or Screwed. On my Prototypes i glue the ButtonBoards with HotMelting Glue and have so far no problems. You might use 2phase Epoxy for even better results.

  • @fcd72 those buttons are so good! Has anyone in USA seen similar buttons from Mouser or any such places?

  • Are you having the panel etched/printed? My plan is to drill the holes and counter sink them then have a lexan overlay made.

  • I’m thinking to go as low budget as possible, so, I may drill it myself. So no rectangular buttons :)
    If I can find a good deal locally I will go for CNC cut panels.

    Also If it is possible, instead of cutting a rectangular hole for the LCD, I will have it sit below the entire panel, then make a stencil and leave a rectangular area unpainted, so that the plexiglass acts as a window. We’ll see about that, though, because I don’t know if the LCD can fit between the PCB and the panel.

  • Then try these Buttons, its 2nd Best

  • Thanks!

    Is there any particular reason not to use the pcb mount switches of the original design?
    I always prefer not to have many soldered wires inside the case, as they are much more prone to fail some time in comparison to PCB mount components…

  • The oposite is true – a PCB is a part that isn’t meant to be bent, with pushing buttons and turning knobs you are constantly putting stress into the whole PCB. But thats just my limited engineers point of view, but there must be a reason why all UI Elements in Space Shuttles, Apollo Spaceships, Nuclear Power Plants and B2 Bombers (and hence the Synclavier) are Panel Mount only.

  • Hahaha! I guess so. It’s that some wires have failed me in the past, that’s why I feel the need to keep it simple :) I don’t think the PCB will bent that much if it’s screwed (btw thanks for your tip, I fixed the screw holes in place!). I will consider your advice, thanks Frank!

    On other news: the Mouser order is going to arrive tommorow. With some luck (or a lot of it) some of the PCBs could arrive this week and I can start soldering!

  • There has been some mention of round button caps on the forum before. I dug these up on the forum but haven’t used them myself.

  • Also you can check if there is a fablab located near you. There you can use a lasercutter to make your panel. Often for very low prices or even for free.

  • Unfortunately, no fablab in Greece :( I should have known, my country is years behind in evolution :P
    I stumbled upon these button caps during my hunt for parts, I ordered some, and I ordered some of these too, just in case I want to lengthen the distance of the PCB and the Panel (to make my display window).

  • These ones are cheap, round and panel mount. I’ll be using them in my 4x4pole build.
    I tested one (NC!) and it works just fine. They are a little small, and there is no tactile click, but for me they will do the job.

  • Fist powerup was successful!

    I did connect the headers of the Digital Control board on the wrong side of the board (I guess the solder fumes got me :P ), but I unsoldered one pin at a time, pulling it out of the board, cleaned the solder with a wick/braid, then put new headers. No harm done! Everything else went smoothly and it worked right off the first powerup. Unfortunately I can’t hear it yet, because the SSM and PT2399 haven’t arrived yet from Small Bear :(

  • Received your board frank! Thanks! (kudos for the soldering superhero pic, too!)
    1) What types are the 100nF caps? Why are they polarized?
    2) The input or the output? Which goes to the Shruthi? Logically it would be the output since the programmer transmits data to the shruthi in a one-way fashion, but looking at the board it would seem that I need to connect the input?

    Another quick question going to everyone, not just Frank:

    What does the SSM2164 do exactly? I powered up the unit without the SSM and the PT2399 (couldn’t resist) and it works normally (without delay, ofcourse). Is it used to mix the dry and the wet signal? That’s the only explanation I can think of.

    BTW, synth sounds awesome, kudos Olivier!

  • No Support Answer:
    Shruthi Digital board -> Programmer -> Filter
    Pin 5 from the 6 In to CV1 In on the Digital Board.

  • SSM2164 is a quad VCA used to control the delay time, wet levels and feedback low/hi levels with CVs.

  • Thanks, both of you!

    @Olivier: So until I get my SSM2164 and PT2399 the synth works normally without Delay?
    @Frank: I think I figured it out. Thanks for your (no) support :) Seems like I’ll have to remove the connectors on the control/filter board and put new ones or solder directly using ribbon cable (at least on one end). I’ll think about it.

    Project Update:

    While waiting on those VCA and Delay chips, I’ll have to:
    1) manually open each pot (oh, didn’t I tell you? they are detented! wtf) and remove the detents. -ouch
    2) go to a local store and buy some connectors (SIL, both male and female, and pins) for interconnections between programmer, filter and control board. Also some wire. Also pins for the other type I used on my MIDI switch. Some solder too (I’m really making my shopping list while posting :P )
    3) get to woodworking! This Saturday I’m going to built the case (except the top and back panel which is going to be made out of plexiglass), so prepare for some photo goodness this Sunday!

    Things are coming along (almost) nicely :)

  • Yes, the upper row of chips is the filter, the lower row the delay and its control circuitry. you can even remove the MCP4822.

  • OK, so the Small Bear package arrived today. I stuffed the two sockets with SSM2164 and PT2399 aaaand… there’s no delay (well, that escalated quickly!).

    I checked the IC orientations as a first start, everything is OK.
    I also tried with a different PT2399 (entirely different batch, had one lying around from a previous echo base build), didn’t work either.
    I also checked other threads (I think it was MicMicMan’s) and read that some people have to try and boot the device a bunch of times until it worked, then it would be a clock latchup problem and I’d have to change a resistor to a different value. I have restarted over 25 times and still no delay.
    I also tried changing the filterboard settings to something else and back to “dly” but to no avail.


  • See the troubleshooting info at the bottom of the delay filter board page.

  • Yes I’m looking into it right now, getting my multimeter ready :)
    I’ll come back with results

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

In this Discussion