as a first module for my kosmo cabinet i want to design a atari punk console as we all know it is originally designed by forrest m. mims and published with other interesting circuits in his engineer’s mini notebook- 555 timer ic circuits. i allready have built a APC a year or so ago and put it into a audio cassette box but failed with the build of an arduino punk console later on, probably due to the fact that the syntax ahd changed and i was not able to get thecode running with the new ide or something 
so this time i want to go modular and start with the APC, a MS-20 and a sequencer and have probably something like this to start playing around 
hope you can help out now and then?
refering to this schematic i want to add voltage control in this design to use it in the synthesizer ecosystem.
to check out how voltage control in general works and what it does to the APC circuit i breadboarded it. the datasheet for the NE556N tells me that voltage control should be between 9V-11V. measured voltages at pin s3,11 are 7,8V while running the APC with 12V. when i touch with the tip of my multimeter there is a small drop? of the voltage and sound changes a little. i got switching jacks for the cv in and use 100K lin pots to ground to dial in voltage between 0-12V. schematic must now look something like this omitting the jacks this time.
i wanted to add switchs to get rid of VC and have the original circuit restored here and add the switching 1/4" jacks inbetween. what do you think about the voltages measured and exposed to the 556IC? should they be limited between 9v-11V? how would a voltage limiting circuit look like? whatelse would you add to that first module?
