MATRIXSYNTH: Portabellabz Sister Card for EMS Synthi Demo

Sunday, January 23, 2022

Portabellabz Sister Card for EMS Synthi Demo

Sister Card for EMS Synthi demo from portabellabz on Vimeo.

Another jam with the Sister Card from portabellabz on Vimeo.

Small jam with the new Sister Card from portabellabz on Vimeo.

Synthi A + Sister Card from portabellabz on Vimeo.

"Portabellabz expansion card for the Synthi A and AKS, mostly intended for the experimental Synthi playing but not only, it's able to create crazy droid sounds as well as subtle modulations (another card more intended for equal temperament will be announced soon, stay tuned ;) ).

In the video oscillator 1 frequency is modulated by the Sister Card's bus 1.
It starts with LFO1 ramp and square, LFO2 is added, then S&H sampling the noise patched via the meter column, slew limiter, S&H + LFOs.
At 1:00 the S&H samples the noise patched via the meter column, normal and slewed outputs, then S&H + LFOs.
At 2:00 I patch the trapezoid fired by LFO2 using an attenuverter pin and then I add bus 1.
At 3:10 back to S&H, the LFO shape changes the "swing" of the modulation.

The card simply plugs directly into the 8 pins Jones "keyboard" socket and is powered by the Synthi, no cables no connector, it's plug and play, easy and hassle free.
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 close to 50mA on each -9V/+12V power rail, which is the maximum a MK1 PSU can handle according to the VCS3 MK1 users manual.
It *should* work with factory condition MK1 units but will push this old PSU to the limits. I assume no liability in case of problem (anyway, it can be repaired, no worries).
In several MKI units (including my own one) I added an extra PSU to power a KS and I'm happy to share the how to if needed.

Features :

Thick PCB for best stability and solidity

2 identical LFOs
Bipolar signal
Square output
Triangle output
Variable shape of both waveforms
Hi/lo range switch
Lowest frequency : +/- 25 seconds cycle
Highest frequency : +/- 90Hz
Frequency LED

Sample & hold
Clocked by either LFO (3 position switch 1 - off - 2)
Sample input via the meter column
Slew limiter with rate pot and lin/log response switch
Normal output
Slewed output
Clock LED

2 identical modulation busses
Individual level pot for each output of the LFO's and S&H
Left bus routed to input channel 1
Right bus routed to input channel 2
Mixed output inverter switch
Level LED

2 attenuverter pins
Scale and invert signal

Gate output
Fires the Synthi's envelope generator by either LFO (3 position switch 1 - off - 2)

It is possible to add a female socket onto the top side of the Sister Card.
The card's and KS CVs are mixed passively via the 100k resistors present on the card's CV outputs and in the KS cable to modulate the incoming CV. If the matrix's rows 8 and 9 are buffered, the pitch and intervals are preserved.
Gates from the keyboard and sequencer, from the card and from the Synthi's EG self-retrig.
With all the card's pots set to 0 and the gate switch in central position, the incoming CV/gate signals are not impacted.

Available as DIY PCB + panel set (€95 shipped) and pre-built (€350 + shipping)."

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