The CV/gate Card for EMS Synthi A / VCS3

The card adds CV/gate facilities to any Synthi to control it with standard 1V/oct keyboards, sequencers, midi to CV/gate converters... or to 1.2V/oct to control it with Buchla equipment.
It simply plugs directly into the 8 pins Jones "keyboard" socket and is powered by the Synthi, without cable or connector.
For use with a VCS3, a second Jones plug can be mounted to the PCB's one to extend it, so it plugs easily into the VCS3's rear Jones socket.
The card works as is with MK1 and MK2 units.
MK1 units don't have the internal wiring used by the card's cv3 input but it can be added, here are the details.


Features

gate input
- accepts signals from +4.5V to +15V
- the incoming signals can mix with the Synthi's looping envelope
- 3 position toggle switch :
    • top - sustained : the on time depends on the gate signal length, ie how long the key is depressed
    • center - off : no gate signal is sent to the Synthi
    • bottom - transient : the gate signal is converted into a short trigger and the on time depends on the on pot setting only

cv1 input
- tracks over about 5 octaves
- CV available on row 8
- 2 position mini slide switch :
    • left - CAL : pre-scaled 1V/oct input with input ch level 1 pot set fully CW to 10
    • right : standard CV input with 100k series resistor for manual scaling with the input ch level 1 pot

cv2 input
- tracks over about 5 octaves
- CV available on row 9
- 2 position mini slide switch :
    • left - CAL : pre-scaled 1V/oct input with input ch level 2 pot set fully CW to 10
    • right : standard CV input with 100k series resistor for manual scaling with the input ch level 2 pot

cv3 input
- tracks over about 5 octaves
- CV available on row 16 if your Synthi is a MK2 with a joystick vertical range switched pot (or a modified MK1)
- pre-scaled 1V/oct input only
- 2 position toggle switch :
    • top : normal CV
    • bottom - inv : inverted CV


The DIY PCB + panel set costs 45€ shipped untracked.
It includes PCB, panel, Jones connector cover, buffer PCB for matrix rows 8 and 9 (I do not supply with other parts).

Users manual

BOM and build notes

A pre-built CV/gate Card costs 150€ VAT and shipping excl.
Contact me to order one.