Synthi POLY MIDI-CV Instruction Manual

Instruction Manual

Switches for DK1/2 or Midi-CV
channel control

Gate Source switch:
Switches between

DK

, midi gates1

-4

Toggle switches for switching
between 1V/Oct or 0.32V/Oct

Synthi A

Synthi

A

POLY

MIDI

-

CV

SYNTHI

A

POLY

MIDI

-CV

INTERFACE

Interface Cables
1x8 way Jones (male)
1x8 way Jones(female)

Midi Learn/Midi
Activity switch

and

LED

Midi In

DK1/2 Keyboard
(optional)

Inverts CV3
voltage

special pin

cable

12v AC/DC
Adapter

2

Instructions on using the Synthi A Poly Midi-CV Interface

This is a Poly Midi-CV (PMCV) unit designed to be used with an EMS Synthi A, either with or
without a Dk1/2 keyboard. It is based around Marc Bareille’s fantastic 3-channel micro-controller
based Midi-CV converter called the ‘MCV876’ (which Marc has kindly allowed me to incorporate in
the modules)

See details of Marc’s unit and all its many features at his website:-

http://m.bareille.free.fr/mcv876/mcv876.html

The latest units I ship have the most recent firmware (v3.06 as of October 2010) for the
Pic18F2320 microcontroller which has faster better performance than the older models (based on
Pic16F876 microcontrollers).

Before Power On

With the Synthi powered off, plug in the two grey cables with the 8 way ‘Jones’ plugs at each end.
The male Jones plug to the ‘keyboard’ socket on the Synthi A, and the female to the DK1/2
keyboard (if you have one). The PMCV unit allows independent switching between a connected
DK keyboard and midi control, through front panel toggle switches. Switch on the Synthi A. Then
plug in the ac power adapter into the rear of the PMCV. You will see the green midi activity led
(top left) flash a few times to indicate all is well.

The midi-cv board in the PMCV is powered by the external ac adapter. But also some power from
the -9V power rail is taken from the Synthi A (via the Jones plug cables) but only a few milliamps.
This is needed for the CV3 voltage inverter. The reason an ac adapter is used is because the Synthi
A has a weak internal psu compared to the later Synthi AKS (and VCS3(mk2)). These latter units
were meant to be able to power external sequencers, so the internal psu is much stronger than in
the Synthi A/VCS3(mk1).

N.B. The toggle switch at top left IS NOT A POWER ON/OFF SWITCH! It is the Midi learn switch
(discussed below) and it should always be kept in the off (up) position in normal use.

The PMCV has no on/off power switch. It is powered on/off when the ac adapter is plugged or
unplugged and when the Synthi is switched on/off.

The Midi Activity Led (green)

This is a multi-purpose led! The led blinks a few times at power on. Then the led will monitor all
incoming recognised MIDI status bytes. The led also blink 3 long blinks if the interface receives the
"Write To Flash" sysex message. When this message is received, all PMCV parameters are written
into the flash RAM. So the PMCV can recall a setup even after a power off. When the interface is
in MIDI Learn mode, the led stays on, until a MIDI message has been received and learned by the
interface. In ‘mono’ play mode (see play modes description below) the midi activity led flashes
when midi notes are received. In other play modes it remains off when midi notes are

3

sent..this is simply to speed up the mid -> cv conversion in polyphonic and multi play modes
where every bit of processing speed is ‘squeezed’ out of the microcontroller.

The "Midi learn" switch

To place the unit in midi learn mode toggle the midi learn switch on then off (down and back up).
The midi activity led stays on until a MIDI message has been received and learned by the interface.
The led will blink 3 long blinks if the interface receives the "Write To Flash" sysex message and will
then automatically go out of midi learn mode to midi play mode.

If you wish to come out of midi learn mode without sending any new configuration data just
toggle the midi learn switch down and up once more. Then the led will switch off and the unit is in
the standard play mode.

Here is how Midi learn works:

When you toggle the Midi Learn switch down then back up the midi activity led stays on and the

PMCV is in Learn Mode waiting to receive a Midi message containing Midi channel information.
When a message arrives ( you play a note on the master keyboard for example) , the Midi channel
number is extracted, compared to the actual interface Midi channel and set to this new value if
different. If the Midi channel of the message is identical to the one configured into the interface,
and if the message received is a Midi note ON message, the interface extracts the Midi number of
the note played and sets this value as the reference (base or lowest ) note. This allows transpose
of the PMCV to any note on the keyboard. The reference note is the Lowest note the interface can
play ( digital zero).

Using the small Windows configuration programme available from Marc’s website you can
configure the unit to any of the available play modes mode as you desire.

V3.06 Firmware and different Play Modes

The PMCV can be configured in these different playmodes using the windows configuration
programme (version 3) which is available from http://m.bareille.free.fr/mcv876/mcv876.html

4

Mono

• CV1-Gate1 assigned to Note On/Off messages

• CV2, CV3,CV4* are assignable to controllers, velocity or PitchBend..

• Gates 2,3,4 are assignable to controllers.

• One channel recognition

Multi2

• CV1/Gate1 and CV2/Gate2 are on channel N - CV1 assignable to MIDI notes

• CV3/Gate3 and CV/Gate4 are on channel N+1 - CV4* assignable to MIDI notes

Multi4

• CV1 to CV4*and Gate1 to 4 are respectively on channels N to N+4

• CVs or gates can be assigned to MIDI notes or controllers independently.

Poly2

• CV1 +Gate1 and CV2+Gate2 are assigned to Note On/Off messages

• CV3 and CV4* are assignable to controllers, velocity or PitchBend..

Poly4

• CV1 to CV4* and Gate1 to 4 are assigned to Note On/Off message

*note CV4 is only available on the 4-channel Quad Midi-CV units.

Triggering the Synthi A Envelope Shaper

The PMCV has Envelope Shaper (ES) trigger assignable to either keyboard (DK1 or DK2 if present)
or any of the 4 gates (gate1-gate4) via a front panel rotary switch. How many of the 4 gates are
available depends on the mode used (see above). E.g. in Poly2 mode, only 2 gates are available
(gate1 and gate2). In poly 4 mode (Quad Units only) or Controller mode all 4 gates are available to
trigger the ES.

Red and yellow panel LED’s light when midi Gate 1 and/or Gate2 are triggered.

Gate 5 and gate 6 outputs are via jack sockets and offer Midi start/Stop and Midi clock signals for
interfacing and synchronizing with other external midi devices.

Using the front panel CV Scaling Potentiometers

CV1-CV3 can be scaled using the 3 front panel potentiometer knobs. These allow different
response to midi generated control voltages. Of particular importance is the fact that EMS Synthi
oscillators use 0.32V/Octave standard NOT 1V/Octave as on most other synths. For pitch CV1 it is
necessary to switch the toggle switch to the 0.32V/Oct setting and scale knob set to maximum
value 10. This will produce correct chromatic scales on Osc1 and Osc2. For CV2 and CV3 you can
either use 0.32V or 1V/Oct setting as you wish for different responses.

The 1V/Oct option is useful if a CV channel is being used as a modulation source rather than to
generate pitch control of a Synthi oscillator. Also if your Synthi oscillators 1 and/or 2 are not
exactly scaled to 0.32V/Oct.. use the 1V setting and adjust the scaling pots until you get proper
chromatic pitches.