Analog modulation matrix / routing

hello :wink:

i’ve been thinking about having analog modulation to the filter and VCA

sources :

  • audio In
  • OSC (raw osc out)
  • audio out (self modulation)

destination :
F (filter freq)

there’s many way to make this, switches, lorlin etc…

but maybe the best way is to make a 3*3 matrix with pots ?
a kind of simplified version of this smart module :

bipolar mode only - i think it can fit in a board same size as shruthi and usuable with other synth / gear as well (think FX).
maybe a insertion would be great (still thinking where)

my questions are :

what do the original CV inputs on the filter board (>F, >Q, >VCA) can handle ?
CV + modulation can be +10V, is it too much ?
if yes, what would be best ?
diode limiting ?
diode rectification ?
a negative offset ? (there will be an unsused AOP on the TL074 that can be used as inverter)

just thinking out loud,

thanks for sharing advices :wink:

5v is Max!

check this thread, where pichenettes explaines diode and opamp voltage follower method to get to 5v cvs.

next time, use search function, to ensure pichenet is not answering a question two times and has enough time left to develop new crazy hardware :slight_smile:

good luck with your mod matrix!

Actually it’s a different matter ; it’s not about clamping the voltage for the ADC on the digital board, but for the CV scaling stuff on the filter board.

Voltage is not directly applied to the op-amp pins so I don’t think overvoltage will be an issue on the filter boards.

Altitude might have an answer as he has modded SMR4 and SSM2044 sidekicks with extra CV inputs.

oops i didn`t realise that.

I did it and it works but its fiddly at best and you really want some kind of attenuator to dial it in. I found that using the CV in pins and and the mod matrix is 100x better and more flexible however.

when you use CV in for FM or AM it gets sampled by the control board at a pretty low rate ?
like going into bitcrusher before modulating if i remember right - don’t have my shruthi under my hands right now :confused:
and that’s cool because it’s unusual :wink:

if you do it the analog way, it’s a whole different sound :wink:

maybe a balance (panpot) setting after the last op-amp would be the best (mix between original and mod)