plans describe a method of adding MIDI capability to the Korg MS-10 analog
synthesizer for $99 with the Synhouse Original
MIDIJACK. Later on, a method to install the Synhouse MIDIJACK
II: Hertz so good! will be described. Some drilling is
required. There is plenty of space on the MS-10 to mount the MIDIJACK
with the provided hardware. With the MIDIJACK, it is possible
to convert the MS-10 to MIDI without removing any circuit boards from the
instrument! The correct analog I/O signals are easy to find and connect
to the MIDIJACK. Like many older synthesizers, the Korg MS-10
has panel-mounted CV/gate jacks with solder lug terminals and the MIDIJACK
wires can simply be soldered right inside the panel. The Korg is
chassis enclosure is difficult to disassemble and that alone takes longer
than the wiring of the MIDIJACK once inside. For this reason,
this particular MIDIJACK installation takes longer than most, approximately
one hour. The 1/4" jacks do not need to be unscrewed from the front
panel. They may be left in place and soldered right on the spot.
You can do this yourself if you have a little experience with electronic
repair and the soldering of wires and circuit boards. If not,
it is recommended that you send the instrument to Synhouse L.A. for a quick,
Installation. The particular installation on which this document
is based was on Korg MS-10 serial #130129, other revisions may be
different. It is best to download these notes and photos and print
them out on paper to look at while working on the instrument and make notes
and check off the steps as you go. As with any project, you
should completely read and understand each step of the instructions before
starting. All repairs and modifications made to your instruments
will be done at your own risk and Synhouse Multimedia Corporation assumes
no liability for personal injury caused or damage to equipment or loss
of use caused directly or indirectly by the use of these plans. If
in doubt, don't do it!
Instructions for installing the Original MIDIJACK:
1) Be sure to have the correct tools and supplies for for the job. If you do not have them, get them. You will need a regular size Phillips screwdriver, a smaller size Phillips screwdriver, needlenose pliers, wire cutters or other flush cut nippers, a hobby knife such as an X-Acto, scissors, a soldering iron, solder, electrical insulating tape, and a black Sharpie permanent ink marking pen. If you intend to mount the DIN jack on the back panel with the rest of the jacks (highly recommended), it is best to use a chassis punch (a small hand tool that safely cuts a clean hole in a metal panel) to make the hole for the DIN jack, and an electric drill with a 1/8" or similar size drill bit to drill holes for the 4-40 hardware used to mount the DIN jack, and also a 1/4" or 5/16" drill bit to make a pilot hole to start the chassis punch. The correct size for mounting a MIDI DIN jack is 14.5 mm metric or 5/8" SAE (.62"/15.9 mm) in American sizes. A chassis punch may be purchased from any good tool or hardware store. If it is more convenient, a punch may be mail ordered via internet or telephone from Mouser Electronics at http://www.mouser.com or (800) 346-6873. The Mouser part number is 586-3803 for the name-brand Greenlee 730-5/8 (about $30). The cheaper house brand part number is 380-0145 (less than $20). The service from Mouser is unpredictable and the house brand ordered by Synhouse for the test installation took three months to be delivered, while the Greenlee part was delivered in one week. Mouser refused to give even a small discount to customers of Synhouse, so no recommendation is deserved or being made here, and any other source you know of to buy this type of tool is highly recommended and certainly a better place to buy from for all of your needs now and in the future. You will also need an 11 mm wrench (for Greenlee) or 1/2" wrench (for the Mouser house brand punch) or adjustable wrench to turn the chassis punch while cutting the hole. An automatic center punch would also be useful. This is an inexpensive spring-loaded pointed punch that can mark your drilling spot without the use of a hammer. Marking the holes with this small indentation will allow you to drill cleanly without slipping and scratching the synthesizer or drilling through your knee. If you choose to mount the MIDIJACK board and DIN jack in the plastic sides of the Korg chassis, the X-Acto knife will carve out the hole quite easily, and will also make the holes for the screws as well, so no chassis punch, electric drill, or drill bits are needed for this alternate quick mounting method.
2) Fully test the Korg MS-10 to be converted to MIDI. Be sure that all functions such as the envelope generator work and that the instrument plays in tune while playing along with a known well-tuned instrument such as a newer digital synthesizer or sampler keyboard. If it doesn't work properly without MIDI, it certainly won't work with it.
3) Extreme caution should be taken while working on the Korg MS-10. The unit should be unplugged while open and even then, the power supply may pose some electric shock hazard due to residual voltage in the power supply.
4) Remove the 18 Phillips screws that hold the top, bottom, and case sides together. This will take some time. Be careful when you lift the top half of the case away from the keyboard because there are two cable assemblies that have very little room to move. One of them goes to the keyboard and the other one goes to the modulation wheel. Mark the polarity of the cables and unplug them from the main board. Remove the screw and nut holding the ground strap to the bottom case. Be very careful.
5) Turn the synthesizer upside down and shake out any dust and debris that may have accumulated inside the instrument over the years.
6) Determine the place where the
MIDIJACK circuit board will be mounted and test fit the board into its'
correct place inside the case. One place to mount it is on the front
panel to the right of the KORG SYNTHESIZER logo. You may choose your
own mounting location, but be careful to avoid putting the board
or wires near the high voltage transformer and fuse connections in the
rear of the instrument. The MIDIJACK hardware packet has paper drilling
templates for easy installation. Use the paper drilling template
labeled MIDIJACK Board Mounting to properly mark and drill the holes with
a pencil, marker, or needle using the paper drilling template
provided with the MIDIJACK hardware packet as seen in this photo called
MS-10pic1 which shows the paper drilling template taped in place:
9) The simple part of installing a MIDIJACK in a Korg MS-10 is that all five necessary wiring connections can be made to the back of the existing analog interface jacks and a single circuit board in the MS-10 (on the back side that is easily accessable) and the entire modification can be performed without removing any boards from the instrument. The MS-10 has panel-mounted 1/4" jacks.
10) The MIDIJACK #1 black and #2
red wires must be soldered in place to get the ground and power for the
MIDIJACK. All of the 1/4" jacks have an unused ground terminal which
is grounded to the chassis. Solder the MIDIJACK #1 black wire to
any one of those terminals as seen in MS-10pic8:
13) The Korg MS synthesizers use
an inverted gate signal similar to Moog synthesizers and the MIDIJACK #7
brown wire (S-trigger wire) works well for this. The MIDIJACK #7
brown wire (S-trigger wire) must then be connnected in parallel with the
existing trigger wire. A small signal diode can be inserted to isolate
the signal so the local keyboard will still work when the MIDI is turned
off. The correct type of diode is included with the MIDIJACK in the
accessory packet, but may also be purchased locally at any electronics
store such as Radio Shack as a 1N914 or 1N4148 or equivalent type of switching
diode. Locate the factory Korg wire which is orange and is soldered
to the back of the TRIGGER IN jack. This wire connects to the tip
of a plug inserted in the the TRIGGER IN jack. Leave it connected
as it is and solder the anode end of the diode (the end AWAY from the little
black band) to this point and solder the MIDIJACK #7 brown wire to the
cathode end of the diode (the end with the little black band). In
summary, the MIDIJACK #7 brown wire goes to the band end of the diode,
the other end of the diode goes to the same terminal on the trigger jack
that still has the white wire with violet stripes soldered to it.
There will now be a factory wire AND a diode connected to this terminal
of the jack. The finished connection with the diode can be seen in
MS-10pic11, but the factory Korg orange wire is hidden behind the
terminal in this photo:
15) The MIDIJACK hardware packet contains nylon cable ties which should be used to tie the MIDIJACK wires into little bundles and to attach them to the factory wires inside the MS-10 now that all connections have been made. This will secure the MIDIJACK wires so they will not rattle and break loose inside the case once the instrument is returned to service.
16) Carefully examine all soldered connections for possible short circuits before closing the instrument.
17) Remount the screw and nut holding the ground strap to the bottom case. Carefully plug in the two cable assemblies that go to the keyboard and modulation wheel, observing the correct polarity of the cables. There is not much room to move, so be careful not to strain anything as you do this. Close the instrument and replace the 18 Phillips screws that hold the top, bottom, and case sides together. This will take some time.
18) Test and calibrate using the procedures described in the Original MIDIJACK Quick Installation Manual.
19) This installation can be completed in one hour.
With the MIDIJACK,
the Korg MS-10 is perfect for computer-controlled live performances with
real-time hands-on sound tweaking and patching. The Korg MS-10 is
quite a bit different than other analog monosynths and the MIDI control
that results from putting a MIDIJACK on it is different as well.
The MIDIJACK is using the Korg's built-in linear-to-exponential converter
to get the correct VCO control. To start playing MIDI, you
must let the instrument warm up then momentarily press down one note on
the Korg keyboard to provide the correct offset voltage. The keyboard
intonation can be adjusted with the knob in the FREQUENCY MODULATION section
labeled EG/EXT. The correct setting will be fairly high, between
8 and 10. If the Korg OCT/VOLT input is working correctly,
the MIDIJACK will play MIDI notes perfectly in tune. An advanced
user may find it useful to add an extra fine tune trimming potentiometer
in series with the EG/EXT knob to get finer control and make quick adjustments
when temperature changes cause drift. The MS-10 keyboard can be used
to transpose the incoming MIDI notes on the fly. If an analog synthesizer
has the built-in glide function factory wired to be pre-CV/gate jacks,
it will not have use of the built-in glide with external CV/gate control.
The installation of a MIDIJACK is no different than using external CV/gate
control, having no access to the built-in glide. If glide is
required for MIDI use, an easy solution for real analog glide is
provided in the Advanced Installation Manual, but is beyond the scope
of these simple instructions.
Instructions for installing the MIDIJACK II: Hertz so good!:
The method of installation for the MIDIJACK II: Hertz so good! is exactly the same for everything except the connections for the MIDIJACK #3 blue wire and MIDIJACK #4 white wire. Instead of being connected to the volt/octave input, connect these in the same manner to the regular Hz/volt VCO input jack. This is so incredibly simple that it doesn't justify writing a whole new article for this method which is only .02% different. If this alternate method is not immediately and completely clear to you, you should refer the installation to Synhouse for Factory Installation. The pros and cons of using the Original MIDIJACK vs. the MIDIJACK II: Hertz so good! are discussed in question 39 on the Analog User FAQ's page.
Possibilities for customization:
An alternate method of installation that would in the style of the fully
patchable Korg MS-series would be to install the MIDIJACK circuit board
inside the synth as intended to get the power for the MIDIJACK from the
synths' internal power supply, but solder the MIDIJACK CV output
wire (MIDIJACK #4 white wire) and S-Trigger output wire (MIDIJACK #7 brown
wire) to a pair of new 1/4" jacks on the panel with the rest of the jacks:
Copyright © 3/19/2001 Synhouse Multimedia