Monotron Duo.

[MirlitronOne]

Since the ribbon resistance change is linear, the oscillator response must be exponential otherwise the note spacing would change along the ribbon.

[sneakthief]

MirlitronOne - the microprocessor takes the ribbon voltage and quantizes it. So you can't make any conclusions about the relation of the ribbon's output to what the microprocessor is putting out.

Notice that a pulse from VCO1 is going back into the microprocessor. I believe that this allows the microprocessor to measure the current frequency and compensate for temperature drifts and other things that affect tuning & scaling (cpu-controlled auto-tune).

chorizu - look at pin 4 of the microprocessor to figure out what V/Octave that the vco's are using.

[chorizu]

@sneakthief-i meassured pin 4 against ground,without activating the ribbon it's 2.96 Volt.When playing the ribbon at goes down to 1.5 Volt on high notes and above 3.16 Volt on lownotes,I'd ressume that it's some feed for the OP

[sneakthief]

Well that seems close to 1V/Oct, albeit if you measured it correctly than it's simply inverted.

The ribbon spans roughly 18 notes (1.5 octaves) and you're getting a voltage swing of 1.66V.

However, please measure again using the chromatic scaling mode! Then you'll know for sure what the internal voltage scaling is.

Anyhow, if you look at the schematic, the voltage from pin 4 of the microprocessor gets added to the reference voltage (VD) then goes to a current mirror (Q1 & Q2) before being sent to the 2 VCO's.

[chorizu]

Yeah,thank You,I'll take me some time to make better meassurements.I ordered some micro equipments on conrad.

[chorizu]

@seakthief-You seem to right,but i first explain my more disinct meassurement: Pin 4 to GND toggles around 2,20 Volt and 1,7 Volt(i dont no why). then i hit a high key it goes to 1,54 stable,then i hit 1octave lower it goes to 2,54 Volt.normaly it must have been reverse?

[sneakthief]

As I said, in this case it just means that the VCO is using inverted 1V/Oct scaling.

If you want to control it externally, then invert the CV with an inverting op-amp

[chorizu]

Yeah,alright,Thank You!

[chorizu]

@sneakthief- i'm a little uneperienced in electronics,is this NAND gate good for my purposes
http://www.stm32circle.com/resources/Datasheets/74LX1G04.pdf

[sneakthief]

http://sound.westhost.com/dwopa.htm#invert

[chorizu]

Thank You,very interesting suggestion and Site, too.First, i have to make oprations on how disconnect Pin 4.

[TakeshiAndTheKid]

Hey there, looking to get one of these things soon. Sad to hear there's no easy way to do a CV Pitch.

There's only one mod I really want to do though, I'm getting one because it seems really awesome for videogamey sounds. To me, having 2 square waves seems kind of redundant so I'd like to change the second square to a pulse, maybe.

Would this be hard to do?

[vonkhades]

Hey guys!

Im tryin to mod my DUO so I can control it externallly... I've read the whole thread but couldnt find info on it ... i've googled a lot but still unsuccesfull to find any info or schematics. The last thing Ive tried was dinsync.info/2010/06/how-to-modify-korg-monotron.html which is for the regular monotron.. but doesnt seem to work... as you said on the last messages the CV wont be easy...



Anyway there a couple youtube users that made some advancements on this.:

http://www.youtube.com/watch?v=ae6t6bN8Pyg
http://www.youtube.com/watch?v=--UNbu23DSY

I've tryied to contact them too, but no answer yet

do you have any suggestions? what pads you solder or a schemmatic/resitor values?? Im sequencing it with a baby10, with both CV and Gate set max outputs to 5v.

cheers!!

[andeje0]

Anyone have any updates on figuring this out?

[Cynosure]

I saw someone posted this - http://www.youtube.com/watch?v=1-E7qPsI4Cw

[andeje0]

Hard to tell if he's really sequencing the pitch there or just the gate and the fiddling with the pitch knobs...will give it a go in the next few days and see...

[andeje0]

Chorizu have you had any luck testing the inverted op-amp to pin 4 of the micro-controller to control the pitch?

[TakeshiAndTheKid]

Is there any way to stop that annoying popping noise you get when you disengage the ribbon controller on the Duo? It kills my ears when using headphones. It's not as noticeable with the filter up but with it down it's unbearable.

[andeje0]

Try reading some of the links of this thread on Muffwiggler -

http://www.muffwiggler.com/forum/topic-47195.html&highlight=monotron+noise

[TakeshiAndTheKid]

[TakeshiAndTheKid]

Ah got it now. I think this is talking more about the background hiss though, and the solution looks very awkward. I get a "tapping" noise when the ribbon controller is disengaged.

[Bozzy]