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The SQ-1 Card for EMS Synthi A / AKS / VCS3

The SQ-1 Card adapts the great small Korg SQ-1 sequencer and adds easy plug and play CV/gate facilities to the Synthi.

The card simply plugs directly into the 8 pins Jones "keyboard" socket and is powered by the Synthi, no cables no connector.
For use with a VCS3, the Jones plug can be mounted onto the top side of the PCB but an adapted umbilical cable with swapped connections is requested, the standard cable won't work.

Warning : the card's power consumption is 155mA on the Synthi's +12V power rail, which is too much load for a MK1 PSU.
It should never be plugged into a MK1 unit, this would fry its PSU. I assume no liability in case of problem (anyway, it can be repaired, no worries).

 An extra PSU can be added to MK1 units to power a KS / TKS keyboard and the Portabellabz expansion cards, here are the details.
Another solution is to power the SQ-1 via its USB port and omit the power circuitry on the card.

Features :

 Thick PCB for best stability and solidity
All the nice features of the SQ-1 are working with the Synthi.

Scaled CV
The SQ-1's CV outputs A and B are routed respectively to the Synthi's input channel 1 and 2. Thanks to a multiturn trimmer, the CV can be scaled to get equal temperament when the Synthi's input level pot is set to 10, therefore no more tricky adjustment is needed to control the Synthi 1V/oct.
A good working and properly calibrated Synthi tracks in tune over 5 octaves with the SQ-1 Card.

The Synthi's envelope can be fired by either the SQ-1's A or B gate, a 3-position switch replaces the SQ-1's former "littlebits OUT" :
left is gate A, center is no gate, right is gate B.

CV/Gate interface
When the SQ-1 is turned off, its CV/gate output jack sockets can be used as inputs to control the Synthi with another controller enjoying its equal temperament 1V/oct scaling.

Handle support
Small plates mounted to the back lock the Spartanite case's handle for better stability.

Control other synths

The SQ-1's ins and outs minijack sockets are still working.
The SQ-1 can control other synths together with the Synthi via CV/gate or MIDI and sync with other gear as a slave or as a master via its sync in and out sockets.

The DIY PCB + panel set costs 95 shipped tracked.
It includes PCB, panel, Jones connector cover, handle support and buffer chicklet (I do not supply with other parts).

Users manual

BOM and build notes


A pre-built SQ-1 Card costs 350 + shipping. The SQ-1 is included and the card comes plug and play.
Contact me to join the waiting list.


Many thanks to Yoshio Machida for the video