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Monotron Duo.
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reve



Joined: Feb 23, 2008
Posts: 147
Location: USA

PostPosted: Wed Feb 29, 2012 2:06 am    Post subject: Monotron Duo.
Subject description: Anyone cut theirs up yet?
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Hey electro-pals.

So along with my usual patch cables I had a bit of an impulse buy at Sweetwater -- picked up a monotron duo.

I was sad to see that it's a bit different from the original... There's no handy "pitch" pad on the back. There are discrete pads for saw, pulse, and square waveforms for both oscillators, though. Pitch appears to swing from 0-3v; gate is + 5v.

There is a "vbias" pad and a "vrib" on the back. Haven't tried injecting anything in there yet. The ribbon appears to be a 10k POT. One of the lines only connects when you press down for gate.

Anyway, I was hoping someone came up with a good explanation of vbias and vrib?

I'll post pics tomorrow if no one else already has nicely annotated photos. Smile

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v-un-v
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PostPosted: Wed Feb 29, 2012 5:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Looking forward to seeing your results. Smile
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MirlitronOne



Joined: Nov 07, 2009
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PostPosted: Wed Feb 29, 2012 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

If you look at the schematic of the original Monotron (available from Korg) you can see that the supplies are unipolar throughout (0V and +5V). Vbias acts as a "mid-point" voltage reference where the circuitry requires it.

The Duo doesn't seem to have arrived in the UK yet, but I'm expecting a Monotron Delay early next week.

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reve



Joined: Feb 23, 2008
Posts: 147
Location: USA

PostPosted: Wed Feb 29, 2012 9:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's the top and bottom of the PCB. Crap resolution on the top, but uh.... I can't imagine it would be too useful to anyone anyway since you ain't tracin' this out from a photo.

Here's the ICs:

Working left to right we have TI MSP430 G2231 microcontroller (surprise!), an LM324, an SN74AHC14 hex schmidt trigger inverter, another LM324, and finally a TPA6111 headphone amplifier.

Given the fact that there's a couple blank pads for missing ICs and caps, additional waveforms and a seriously underutilized microcontroller, I think it's safe to assume that the Monotron Delay uses essentially the same board.


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Monotron DUO PCB bottom
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DSC01617.JPG



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jonnyj



Joined: Jun 09, 2010
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PostPosted: Fri Mar 09, 2012 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi that's the point where I am at now. I noticed right away the Duo is laid out a little differently. I opened up the Duo and can clearly see the "gate" point but no "pitch" point labelled like on the original. While I have mine opened I would like to solder the wires for the simple note on/off for CV/Gate etc so I can play or sequence it with something. What point do I need to solder for pitch? Confused
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corex



Joined: Mar 02, 2010
Posts: 114
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PostPosted: Sat Mar 10, 2012 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Seems like 'VRIB' should do something, like add your CV to the ribbon wiper voltage.
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avantronica



Joined: Sep 07, 2008
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PostPosted: Mon Mar 12, 2012 4:21 am    Post subject: Reply with quote  Mark this post and the followings unread

thought i'd share my 'mods!' whilst i too ponder some electrical ones .... i'd love to know whether anyone has sight of a suitably small multiconnector which will live neatly in/on the monotron family cases, something to breakout from, i have all the korg ribbon stuff and the duo has the most 'patch' points


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corex



Joined: Mar 02, 2010
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PostPosted: Mon Mar 12, 2012 9:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice. I'Ve been meaning to do that to my tiptop 808 modules. Looks good.
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avantronica



Joined: Sep 07, 2008
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PostPosted: Mon Mar 12, 2012 10:48 am    Post subject: Reply with quote  Mark this post and the followings unread

tools reqd: water-based paint, pin, fingertip, patience
with the 'tribe I found some letraset capital I letters worked a treat

looking fwd to see what folks do mod-wise with the delay/duo


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houshu



Joined: Sep 02, 2008
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Location: Saitama JAPAN

PostPosted: Thu Mar 15, 2012 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Schematics of Original Monotron, Monotron Duo, and Delay are available at:

http://www.korg.co.jp/Product/Dance/schematic_archive/
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picsynth



Joined: Oct 16, 2008
Posts: 27
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PostPosted: Fri Mar 16, 2012 12:05 am    Post subject: Monotron delay resonance mod Reply with quote  Mark this post and the followings unread

Hi all,
I put back the resonance control in the monotron delay last night, here is how

http://picsynth.000space.com/monotron/monores.html

more mods on their way soon!
Kevin
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v-un-v
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PostPosted: Fri Mar 16, 2012 2:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice mod Kevin! Very Happy
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ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
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jonnyj



Joined: Jun 09, 2010
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PostPosted: Sun Mar 18, 2012 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

corex wrote:
Seems like 'VRIB' should do something, like add your CV to the ribbon wiper voltage.


Thank you for the reply. So far I have only soldered one wire to the DUO's Gate pad.

I ordered this board made for the Monotron http://www.midi-hardware.com/img/minicv.jpg which should make things a little easier however the directions show connecting the Gate and the Pitch for the original Monotron.

I am getting little frustrated wondering what I am going to do to access the Monotron's 's' power after the DC Booster. I am told to use a volt meter to find it but then what for a noob like me? I know more than I think I do but I can't afford to screw this up.


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corex



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PostPosted: Mon Mar 19, 2012 9:31 am    Post subject: Re: Monotron delay resonance mod Reply with quote  Mark this post and the followings unread

picsynth wrote:
Hi all,
I put back the resonance control in the monotron delay last night, here is how

http://picsynth.000space.com/monotron/monores.html

more mods on their way soon!
Kevin

This occurred to me as well -- I'd love to hear some samples.
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joe



Joined: Mar 20, 2012
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PostPosted: Tue Mar 20, 2012 7:23 am    Post subject: Monotron Duo Reply with quote  Mark this post and the followings unread

Just a quick summary:

- Vbias is the +3.36 "middle" voltage between GND and VCC.
- It is generated by IC3A
- The MSP430G2231 is a microcontroller from TI that could be possibly reprogrammed by me to directly add a MIDI input to the Monotron Duo!
- The microcontroller provides a Pulse-Width modulated Square Wave in
order to control the VCO CV (0V-3.3V) + it outputs a 3.3V Gate signal.
- The filter has key-tracking as in the previous version
- I'll try removing the headphone amp and the DC/DC booster, as it seems that the noise comes from these
- I'll add direct 5V input for the Monotron and see what we can do to make it work with a symmetrical -5V 0V +5V supply (think of modular)

This is just what I see from the Monotron Duo schematic. I hope to get my monotron soon. Would anybody be interested on a minimal MIDI mod for the Duo (with Filter CV control)? It might be possible that I'll make some PCBs.
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Danno Gee Ray



Joined: Sep 25, 2005
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Location: Telford, PA USA

PostPosted: Tue Mar 20, 2012 6:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would be interested in one of those boards.

On an aside, can anyone confirm that a value of "NU" on the Monotron Duo schematic indicates "Not Used" ?
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Napalmtree



Joined: Mar 22, 2012
Posts: 3
Location: Austin, TX

PostPosted: Thu Mar 22, 2012 5:18 pm    Post subject: MIDI-IF
Subject description: stuck
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Had my Monotron Duo for a couple weeks now. Just put together the MIDI-IF kit but I'm stuck as well. Firstly, the missing Pitch CV. Also, I remember there's a resistor on the original monotron that needed to be desoldered to permanently disconnect the ribbon and well the bits are definitely different. The button for scale changes may have something to do with it. If anyone else finds the solutions I'd love to hear. I'll let you know if I manage to hack it right.
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Napalmtree



Joined: Mar 22, 2012
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Location: Austin, TX

PostPosted: Thu Mar 22, 2012 7:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

doh
Last edited by Napalmtree on Sat Mar 31, 2012 10:33 pm; edited 1 time in total
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SPIKE the Percussionist



Joined: Jun 06, 2006
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PostPosted: Sat Mar 31, 2012 2:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Finally picked up a DUO today!
(Of course I went to GC for something that just sends MIDI clock...to no avail.)

Anyhow...I haven't had this thing for an hour and what do I do?
Come here to see what you guys have done to them!

;P

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Napalmtree



Joined: Mar 22, 2012
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PostPosted: Sat Mar 31, 2012 10:32 pm    Post subject: no luck Reply with quote  Mark this post and the followings unread

multimeter, there must be a sweet spot for that pitch wire.
Last edited by Napalmtree on Fri Apr 06, 2012 12:52 pm; edited 1 time in total
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jonnyj



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PostPosted: Thu Apr 05, 2012 11:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Please let us know if that ends up being true. If that's the case then that would be a whole easier than the other ways at leas having that one place to plug into however it is still soldering as opposed to plugging into a serial port as on the Monotribe. I consulted with two people about the DUO board and neither one could say for sure what exactly is needed to have basic MIDI control without a lot of trial and error ie. soldering and de-soldering if the one idea didn't work.

JJ
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nickstomp



Joined: Apr 16, 2012
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PostPosted: Tue Apr 17, 2012 12:13 am    Post subject: Monotron DUo MOD
Subject description: MSP430 datasheet
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Msp430 datasheet

http://www.ti.com/lit/ds/symlink/msp430g2231.pdf

it's the same microcontroller of the TI launchpad!!!!!!

http://processors.wiki.ti.com/forums.html/MSP430_LaunchPad_(MSP-EXP430G2)

if they do it to be modded the processor is not write protected
P1.7 and P1.6 are free so maybe a software uart???
It they don't have put it already someone with a monotron duo and an oscilloscope out there?

they put all the pin on a test point so with a jtag programmer it can be read/written I think

Now I'm working to rehouse my monotron delay to add resonance control/ lfo that control cutoff and pitch, CV input

I think that with a pic and a dac (or maybe a pwm output) that replace ribbon controller all the monotron pitch can be controlled by midi/some other stuff!!! the ribbon is basically a 0-5v pot!!!!
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jean-louise



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PostPosted: Fri Apr 27, 2012 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi, a friend of mine has got a monotron duo and we were doing some multimetering the other day to find out if there's a sweet spot for pitch CV.
I haven't got the measurement results with me now, but I remember the following:
The pads labeled SAW1, SAW2, SQU1 etc. gave us steady voltages no matter whether the ribbon was pressed or not or where on the ribbon.
The pad labeled Vrib gves the output of the ribbon voltage (hence the name) and it goes from a low voltage (I don't remember if it was zero volts) to full voltage (3V).
There also is a point we found using the schematics but there's no real pad connected to it, only one of these really small hole-y things (don't know what they're called - solder-hole?).
This point is at the joint of the pitch output from the MSP430G2231 (pin 4) with R7 (56k). R7 is located in an array of resistors on the side of the board near the MSP430G2231. It's the resistor in the right bottom corner.
Without pressing the ribbon this point puts out some changing voltage much like an lfo (it sounds like an lfo too when you send a gate to the monotron but no pitch CV).
When the ribbon is pressed it puts out varying Voltages. We found out that it uses 0,23V/Oct. but mirrored, so that for instance the low C is 0,23V above the high C.
However when we tried to input some Voltage there nothing changed, the monotron was just playing the same low modulated tone.
These are our results so far, maybe someone can figure out what that means?
cheers
jan
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chorizu



Joined: Apr 28, 2012
Posts: 8
Location: Heidelberg/Germany

PostPosted: Sat Apr 28, 2012 6:17 am    Post subject: Monotron Duo Schematics Reply with quote  Mark this post and the followings unread

Hi people,
i try to mod my monotron Duo.I've measured vrib against gate, and played on the ribbon controller.The multimeter showed diffrrent Volt status, like to be needed to feed in CV in vrib while gate is active.IT'll take me time to to build a midi-mod for the DUO.I'll write back.
Buenos,Chorizu
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chorizu



Joined: Apr 28, 2012
Posts: 8
Location: Heidelberg/Germany

PostPosted: Sat Apr 28, 2012 9:31 am    Post subject: Monotron Duo Hz/OCT? Reply with quote  Mark this post and the followings unread

I measured vrib to gate while playing on the ribbon and it showed a differrence of 2 Volt between 1 Octave.The Conclusion is the CV reacts in Hertz/Voltage ratio( Hz/Oct like the old MS20).Has anyone same Results?I read that MS20 and MS10 had an external Pot to lower the Rate to 1V/OCT.But Hz/Oct is exponential und V/OCT linear.If the monotron duo pitchscale is really Hz/OCT how do i modificate it?
Ciao,Chorizu
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