Korg Monotribe modifications thread

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pulse_divider

Post by pulse_divider » Tue Jul 26, 2011 4:09 pm

mckenic wrote:Dont know if its that my ears are old & shot, the beers Im drinking, youtube or my monitoring set-up... I certainly can hear changes on the snare and hats but no difference on the Bd :despair:

Still - exciting times :hyper:
The kick decay only seems to affect the low frequencies, not the attack.
And the snare decay knob affects the pitched portions while the switch affects the noise.
Pretty cool! I listened on my Ipad earlier and thought "meh" but now that I'm in the studio in front of the monitors it sounds worthwhile.

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Post by mckenic » Tue Jul 26, 2011 4:19 pm

Ah! Thanks!

The fan on my laptop kills low freq listening so I'll have to listen with headphones! I just thought I was too old to hear it :)

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Post by th0mas » Tue Jul 26, 2011 6:39 pm


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Post by darenager » Wed Jul 27, 2011 11:17 am

I think I'd be inclined to go for some less subtle mods, I think the monotribe kick is perhaps a little too low in frequency for my taste so I might try to have it a bit more punchy.

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Post by glitched01 » Wed Jul 27, 2011 11:22 am

If the community figures out the CV/gate/trigger stuff, the Monotribe will go down as the most affordable semi-modular "groovebox" ever!

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Post by Veqtor » Thu Jul 28, 2011 4:46 am

New definition of misjudging the electronic music instrument market:
1) Build a device that replicates a tb-303 but with ms20 filter and three analogue drum sounds + performance sequencer
2) Hype it all over the web
3) Make ~500
4) Sell them for €150 each
5) Get surprised when they sell out

----------------

Oh well... I got to try one today, I must say it sounds a lot better than in the pesky youtube and mp3 demos I've heard, the bass rips through really well and the snare has enough punch, also wondering if they've implemented some kind of cheap compressor or saturation on the output amp because the mix sounded really thick and punchy. I hope they don't realize how good it is given that I think a lot of ppl would buy it even if it was priced at ~€250.

I hope its internal gate signals are strong enough to clock my modular, I hope to compliment it with a uZeus skiff running off a battery-pack containing a René, phonogene, modemix and maths, if I can squeeze that in there. Would be ideal as modular busking system :razz:

-------

On the mod side of things:
What about using a NSL32sr3 for cv control of the decay times?

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Post by phono1337 » Thu Jul 28, 2011 6:55 am

Veqtor wrote: tb-303 but with ms20 filter
thats pretty far off tbh ;-)

























(ok i'm a purist)

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Post by goiks » Thu Jul 28, 2011 10:23 am

Veqtor wrote: I hope its internal gate signals are strong enough to clock my modular, I hope to compliment it with a uZeus skiff running off a battery-pack containing a René, phonogene, modemix and maths, if I can squeeze that in there. Would be ideal as modular busking system :razz:
just got a monotribe yesterday, sounds great with a little gain from my metric halo box. been clocking this from it, running everything from a uzeus, very fun combination! veqtor, make me a battery pack while you're at it!



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Post by chando » Thu Jul 28, 2011 9:42 pm

Maybe I'm crazy .. but I wouldn't even waste my time modding the drums :despair:

Individual outputs would be very tasty.. but once again I need a way to turn off the oscillator so it can be a decent filter... if not I'll just keep waiting and praying for a decent deal on a Waldorf MiniWorks desktop..

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Post by aksen » Thu Jul 28, 2011 10:04 pm

chando wrote:but once again I need a way to turn off the oscillator so it can be a decent filter...
yeah, curious why they went backwards on that feature from the monotron.

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Post by chando » Thu Jul 28, 2011 10:14 pm

But the Monotron was just free running.. no real fun there.

Dammit!! I just want a filter that I can sequence. My SH-7 did it really well but that was overkill..

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Post by Nils » Fri Jul 29, 2011 1:31 am

would a mod converting the mono audio output to a stereo output (tip - synth, ring - drums), be doable/easy? I don't want to modify the housing..

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Post by Low-Gain » Fri Jul 29, 2011 7:30 am

Just an FYI... the 9V adapter input on the back is not a standard 2.1MM plug.. I plan to mod mine to take a normal Boss style center negative (isolated jack) 2.1mm 9V wallwart. To make life a little easier.

Batteries last a little while, but not long enough.

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Post by Sir Ruff » Fri Jul 29, 2011 8:37 am

goiks wrote:
Veqtor wrote: I hope its internal gate signals are strong enough to clock my modular, I hope to compliment it with a uZeus skiff running off a battery-pack containing a René, phonogene, modemix and maths, if I can squeeze that in there. Would be ideal as modular busking system :razz:
just got a monotribe yesterday, sounds great with a little gain from my metric halo box. been clocking this from it, running everything from a uzeus, very fun combination! veqtor, make me a battery pack while you're at it!



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wow... that's a beautiful case/setup - I'd be curious to see what modules you've actually got in there (being less familiar with euro stuff at a glance)

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Post by goiks » Fri Jul 29, 2011 10:31 am

Low-Gain wrote:Just an FYI... the 9V adapter input on the back is not a standard 2.1MM plug.. I plan to mod mine to take a normal Boss style center negative (isolated jack) 2.1mm 9V wallwart. To make life a little easier.

Batteries last a little while, but not long enough.
i went through all the different adapter tips at radio shack and none fit, i read somewhere that the korg ka350 ac adapter will work, but haven't tried it yet. kinda lame that it's not included, they must haev been really trying to keep the price down.

@ sir ruff- thanks, that's most of the makenoise lineup, and the harvestman's oscillators, with a ustep and uscale from intellijel.
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Post by Low-Gain » Fri Jul 29, 2011 10:40 am

yeah. i'll look at the foot print. can probably swap out the connector for a standard 2.1mm.. I'll likely just drill a hole in the back and mount one of my panel mount 2.1mm connectors that i use on FX pedals.
simple fix.. 3 wires... 1 hole, 1 connector.

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Post by nitro2k01 » Sat Jul 30, 2011 8:40 pm

Considering software hacks... Most likely they've set the protection bit so that the current software can't be dumped. If one were to try and develop an alternative software, you would lose the original firmware as soon as you upload a your own stuff for the first time. If I'm not misunderstanding the documentation for the microcontroller, there's also away to lock the flash from being written to, which would mean that software hacking isn't possible at all, unless you replace the microcontroller chip. OR in the best case scenario they've just left it unlocked. I'll try to investigate.
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Post by dualmono » Sat Jul 30, 2011 9:16 pm

Just for completeness:
Keep an eye on this blog.
ImageImageImageImage

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Post by StepLogik » Sun Jul 31, 2011 6:26 am

Interesting choice of CPU. That is a 32 bit model and also has a lot of extraneous features that seem completely unnecessary for the Monotribe.

Also interesting is the 10 channel A/D converter and no D/A facilities that I can see. I'm guessing they are using an external D/A, probably connected via I2C. I'm curious as to what those 10 A/D channels are used for. Seems like only 2 or 3 would be needed: input for the ribbon, input for the VCO output for continuous pitch calibration, maybe an input for the tempo knob. Seems like the rest of the knobs would be connected directly to the analogue hardware.

Can't wait for schematics for this thing, either reverse-engineered or official ones from Korg!

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Post by nitro2k01 » Sun Jul 31, 2011 8:31 am

StepLogik: Actually only 8 channels, but that chip is the lowest spec chip in that group of microcontrollers. As for it being a 32-bit model, that really makes sense. The math required for the pitch detection/calibration (and maybe other things) becomes so much easier when you have more bits than 8 to do math with. Perhaps one ADC channel is used for the sync input as well, but that remains to be seen. That might just as well be done with analog+discrete digital circuitry, (comparator+level shifter or something) and then a digital pin connected to an interrupt.

Also, you wont see any official schematics for this from Korg, I don't think. ;)
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Post by StepLogik » Sun Jul 31, 2011 3:46 pm

nitro2k01 wrote:StepLogik: Actually only 8 channels, but that chip is the lowest spec chip in that group of microcontrollers. As for it being a 32-bit model, that really makes sense. The math required for the pitch detection/calibration (and maybe other things) becomes so much easier when you have more bits than 8 to do math with. Perhaps one ADC channel is used for the sync input as well, but that remains to be seen. That might just as well be done with analog+discrete digital circuitry, (comparator+level shifter or something) and then a digital pin connected to an interrupt.

Also, you wont see any official schematics for this from Korg, I don't think. ;)
Def agreed on the 32 bits. That combined with the number of timers available on that model also makes me wonder if some envelope calculations aren't being done by the CPU as well.

Yeah, I doubt Korg is going to release these schematics! :bang: But, I'm hoping someone will reverse engineer it. I'm very curious to see how much is actually implemented in hardware vs. software.

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Post by computer controlled » Mon Aug 01, 2011 3:56 am

I wonder how easy it is to drill through that case.

I also notice the pots work backwards. What's up with that? :despair:
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Post by th0mas » Tue Aug 02, 2011 11:29 am

The first thing I would do is wire up the standard MIDI optoisolator circuit and connect it to all the hardware UART pins on the CPU. It's possible there's code on there to listen for MIDI input but they left off the circuitry to save money...

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Post by Low-Gain » Tue Aug 02, 2011 10:39 pm

Image

Sorry for the crap picture.. i dont have photoshop installed yet.
And i dont know how to use Gimp. lol. Center lug on the VCA pot is the VCA output... and the 3 positions on the waveform switch are the individual wave outputs.

I tested these tonight.. haven't wired them up yet. but they work.. use a 150-1000 ohm resistor on each output.

Enjoy!

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Post by nitro2k01 » Wed Aug 03, 2011 9:22 am

CONFIRMED! It is actually spitting out proper MIDI on the serial line! It gives you the following:

Note data.
MIDI sync, incl. start and stop messages.
Automation data for all of the LFO settings (both the knobs and the switches) and the EG shape. This suggests that the LFO and envelope may be created in software.

I have not yet hooked up an optocoupler and fed the thing MIDI from the other end, but I will. Shorting the serial out and serial in ports glitches the thing, so it most probably is capable of receiving MIDI.

Here's the pinout for the pin connector marked serial on the board.

Code: Select all

CN12	MCU
1	Pin 20 PH0, TB0IN0, /BOOT
2	Pin 12 RXD0
3	Pin 11 TXD0
4	Pin 9  Vdd &#40;3 V&#41;
5	Gnd
6	Pin 29 PF6/SCK1
I believe this header was intended for factory programming of the firmware. When pin 1 is held low, the MCU enter a special programming mode, according to the datasheet. Pin 6 goes is routed up to somwhere near the power switch and is probably used to detect when a unit is turned on to begin the programming.

CN13 (which comes with no connector attached) would be used for debugging, but it is likely that debugging is disabled so you can't dump the firmware etc. Still haven't looked into that. (I don't have JTAG tools readily available, so...)

But what we're interested in is pins 2-5. Pin 2 is for receiving MIDI. Pin 3 is where MIDI comes out. If you're going to try to add an optocoupler, you'll also need Gnd and Vdd.

MIDI is a current loop protocol, so 3.3 V is no problem for standard MIDI gear given that you adjust the output resistors accordingly. Following the standard MIDI convention, I connected 3.3V and the output as usual, but replaced the usual 220 ohm resistors with 150 ohm ones. Works well enough.

I also got an idea: If the monotribe can receive MIDI, that may open up the possibility of throwing the internal oscillator out the window and using the it as a self-tuning MIDI CV interface for modulars. However, I've found that at least my monotribe tracks badly and sometimes drifts a little. This is especially obvious when comparing it to a well-tuned computer playing the same MIDI notes. Also, it's using just 5V internally for the analogue part (3.3V for the digital) and the CV range may be even less, so perhaps it wouldnn't be of much use for 1 V/oct systems.

More to come...
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