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Adding a Frequency CV Input to the Yusynth/Oakley S/H
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Adding a Frequency CV Input to the Yusynth/Oakley S/H
defutura
I like changing the sampling frequency/rate of the S/H live, but if I want to control it via CV I have to tie up a separate LFO that has an FM input and use that as an external clock. Which seems a shame, seeing as the S/H modules all have internal clocks...

I've looked at the different S/H modules available in MU/5U (MOTM101, Dotcom, Yusynth, Oakley), but none of these allow external control of the internal clock.

So, how difficult is it to add CV control of the internal clock to the Yusynth (or Oakley) S/H circuits?

For reference, here's the schematic for (what I assume is) the internal clock part of the Yusynth S/H:



Thanks!
Synthbuilder
defutura wrote:
So, how difficult is it to add CV control of the internal clock to the Yusynth (or Oakley) S/H circuits?


The Oakley is clocked by an internal VCO. Alas there was no space on the front panel for a CV input but it should be relatively easy to repurpose one of the sockets for voltage control of clock frequency. You'd just need to add a 100K resistor in there, which joins your new socket to the summing node for the VCO. The summing node can be found at the middle pin of Q1.

Tony
Troubleshooter
Building a VCO around a single opamp is possible but the cirquit is too diffrent from the one you have allready.
Therefore the simpelest way to get to your goal seems to be a little dedicated VCLFO breakout pcb. Many cirquits available out there such as the simple 555 VCO.

I also built the Yusynth S+H noise combination. Use the internal clock for the drone/scifi sounds, and external clock for random clocked step filter effects etcetera. If I ever need to cv the clock I wouldnt mind dedicating one of my 2 VCLFO's.
defutura
Thanks, Tony and Troubleshooter!

So it's that easy to add CV in to the internal VCO on the Oakley? Like this?



No need for any input/output protecting diodes or anything?

Some of the other threads I found on similar topics (i.e. adding CV control to any potentiometer) suggested replacing the potentiometer and its opamp with a little vactrol or opamp VCA, but this seems so much simpler...
Synthbuilder
defutura wrote:
So it's that easy to add CV in to the internal VCO on the Oakley? Like this?



Yes that will do it. Although I'd make the CV input socket normalised to 0V to minimise any interference when there's nothing plugged into it.

Tony
defutura
Synthbuilder wrote:
Yes that will do it. Although I'd make the CV input socket normalised to 0V to minimise any interference when there's nothing plugged into it.


Thanks. I'm not quite sure what that means in practical terms, though. Like this (I'm just feeling my way here...)?



Also, do you have any suggestion on where on the PCB I should connect this jack to 0v?
Synthbuilder
defutura wrote:
do you have any suggestion on where on the PCB I should connect this jack to 0v?


The normalising lug can be taken to 0V anywhere on the board - there's numerous spots to use. But pin 2 of the power header would be handy.

The sleeve connection of the socket can be taken to pin 3 of the power header. Pin 3 is also 0V but is reserved solely for the sleeve connections of the sockets. Pin 2 and Pin 3 are normally joined together at the power supply.

Tony
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