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Adding CV In/Trigger to an Old Synth
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Adding CV In/Trigger to an Old Synth
goyousalukis
Hey guys,
I picked up a Moog MinitMoog synth from the 70's. I am currently restoring it. I would really like to add a CV in and Trigger, so that I can control it from a sequencer. I see a lot of mods to add CV out, but not so much for CV in.

Can anyone point me in the right direction? I've attached the keyboard part of the connection. Can I just connect the incoming CV to the opamp that the keyboard connects to ? And then I am unsure how the gate would be connected.
Any ideas / help would be appreciated.

Thanks,
Justin
neurofun
The following links explain how to connect a midijack(midi->cv, gate) to a minimoog. Together with the schematics you should be able to figure out how to achieve what you want.
http://www.synhouse.com/m1-quick-installation.html
http://www.synhouse.com/Minimoog-notes/Minimoog-notes.html

Don't forget the minimoog uses s-trigger, so you will probably have to covert the v-trigger from your sequencer to s-trigger.
Graham Hinton
goyousalukis wrote:
Can anyone point me in the right direction? I've attached the keyboard part of the connection. Can I just connect the incoming CV to the opamp that the keyboard connects to ?


No. The keyboard output goes through R68 (150k 1%) to the summing node of the DC Summer which is above the schematic you showed. You need to add another resistor going in to that node. To work out the value measure the "keyboard control voltage" change going in to R68 when playing two notes an octave apart and scale 150k accordingly.

Quote:

And then I am unsure how the gate would be connected.


For a positive gate you need another diode and 2k2 resistor joining the signal called "Trigger" on the right.

neurofun wrote:
The following links explain how to connect a midijack(midi->cv, gate) to a minimoog.


Not much help when he's got a Minitmoog.
goyousalukis
Thanks Neuro - Looks like I have some reading to do!
goyousalukis
Thanks Graham!
goyousalukis
Graham,
Your website and products look amazing! Thanks for helping me out!
Justin
stepbysteps
thx
neurofun
Graham Hinton wrote:
neurofun wrote:
The following links explain how to connect a midijack(midi->cv, gate) to a minimoog.


Not much help when he's got a Minitmoog.

oops d'oh!
goyousalukis
No Worries Neuro - I appreciate your taking the time to reply!
goyousalukis
Hey Graham,
I just wanted to say thanks - I am making progress!

I had to amp the 5V gate up to the 8V that the synth expects, and the CV is a bit of a challenge, since the MinitMoog uses 3 volts per octave versus 1 volt. In this video, I am sending the CV from an Arduino with a DAC. In the end, I think I will go with Midi In, since there are good midi libraries for the Arduino, and also so that I can easily prevent sending more than 4.5V to the synth. Also, if I get ambitious, I could add some other controls to the midi, like the filter, and modulation, etc...

https://www.youtube.com/watch?v=tqlTVQt2jME
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