Crumar DS2 Midi kit (A03.1 duo)
This is upgraded version with two boards that can set independent MIDI channel for each part of synth. Octave transposing through MIDI is not allowed on this version of board.
Please read instructions twice before start doing anything.
Welcome to the metric system zone. Here we work with precision things and all dimensions are metric. 1" = 25.4mm.
Installation:
To your good usability select the friendly place to mount the LED, DIN5 MIDI connector, button and PCBs. Mount connector, LED and button before soldering wires.
Important:
For organ key contacts you need to be isolate ground bus. It can do extra cacophony-humming noise on output, but if not do it - MIDI for organ section won't be working.
Use packing tape or something like this for that. You can also remove this bus, but you will need to solder jumper wire for connect ground wire from other side to restore connection. See pictures below.
Drill dimensions:
MIDI jack (DIN5) = 18mm.
LED holder = 6mm.
Push button = 12.5-13mm.
Be careful with drilling hole for push button, it have so small range to get hole too big. See below dimension ranges from their datasheet. Drill a bit less and file it to fide fitting.
Board dimensions and distance between screws:
Dimensions 102x50mm. Height 14mm with inserted connectors.
Holes diameter 3.5mm.
Mounting outline and hole drills draft for board example sticker paper included for both boards.
Do not allow the board to bend, it can break the board.
After mounting boards, connect boards together with 10pin cross board cable and 8pin cable.
Ribbon cables are 90cm. long, enough for placing all connections and you can cut extra length. Except 8pin and 10pin cable.
The next picture shows the pinout for 14 and 8 wire ribbon cables. And also pin number of wires: Same orientation when board facing to you.
More visual wiring:
(7) V+ should be soldered to 2.2uF capacitor.
(8) GND to any ground (green wires on power supply).
Board pinout and MIDI chart:
Board_1 is for POLY part of synth. Board_2 for MONO part of synth.
Here is two almost identical boards that have cross connected between each one by small 8 and 10pin ribbon cables.
Under keyboard you can see two key contact groups of contact springs. At this point your brain can blow. Let me explain:
Solder first one group of contacts for board 1, then go to the second group and board 2. Find key contacts for note F on the first octave and solder wires from the YELLOW connector. Starting from wire 1. When you finish it, your last wire will be 12 and note E on this octave. Your move will go from left to right. All others octave absolutely same.
Wires marked "skip" should be skipped except wire 13 which should be soldered to key contacts common bus, every for every bus. For Board 2 - repeat the same.
Wire colors to key contact may vary, and can be not in the same sequence on ribbon cables. But always first wire is first to you if board placed as to this picture below:
J1,J2,J3,( J5 on bottom side) should be close.
Boards pinout:
Board_1 POLY.
Here is some visual explanation:
On picture below is shielded cable, shield is ground wire that soldered to ground bus. If you going to remove this bus in case if you will not put insulation space where is contact spring touching it. You need to solder jumper wire to left side of keyboard. Because it have connected on opposite side. White center wire is POLY common bus, here is should be soldered common wire №13 from X4 connector at Board 1.
So, looks like installation finished. Now time to explain how set MIDI channel. This is what you need to know for starting use this retrofit.
Process for set MIDI channel: User operations
Stop all MIDI traffic.
To teach with which MIDI channel synth will work. MONO section: push and hold the LEARN button for a 1-2sec. LED will blink fast four times and stay ON to wait for MIDI messages at one of 16 channels.
Send any note on the MIDI channel which you want for this synth.
When the synth receives MIDI messages, LED will blink fast four times and turn OFF. It indicates that channel was received and saved. Then will ON with every NOTE ON messages on the selected channel.
For set MIDI channel to POLY section : push and hold the LEARN button for a 2-4sec. LED will blink slow four times and stay ON to wait for MIDI messages. Of course you can set both channels is same.
Now the channels saved to memory and will never change before you initiate the settings process again.
In case of PANIC, or you want to exit from settings - Short push the LEARN button.
PANIC - Short push
POLY - Push for 1-2sec. LED blink fast.
MONO - Push for 2-4 sec. LED blink slow.
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At moment when synth power on, all keys will be sound less a half second. If on this moment MIDI commands will received on saved channel it can be cause of panic.
This manual can be not so much clearly to understand, and may be edited for fix it without notification.
Last change: 14 April 2026
