Do It Yourself Special:
    FREE plans to add MIDI capability
    to the Korg MS-10 with the
    Synhouse MIDIJACK!
     
     

         The following 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,  low-cost Factory 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:
     

     
    Once taped in place,  the holes may simply be center-punched and drilled through the paper.  The perfect size drill bit for the switch stem and two screw holes is 9/64",  and the perfect size for the scale adjust trimpot is 3/16".  Drill the holes.  A photo called MS-10pic2 shows the location of the newly drilled mounting holes:
     
     
    7)  Temporarily mount the MIDIJACK board in place.  When mounting the MIDIJACK board,  the switch should be fitted so well in the panel that the switch stem will not wiggle at all once in place.  It should not have any free play but also should not be so tight that it binds.  When the switch is pressed,  it should have a definitive "click" and bounce back like the button on a new VCR.  You will never regret spending too much time on this and good attention to detail will make the perfect MIDIJACK installation.  The hole in the panel that is over the MIDIJACK scale adjust trimpot should be approximately 3/16" so a Synhouse Pocket Screwdriver can fit through the panel for periodic adjustment.  Once the fitting is correct,  tighten the screws.  The new installation of the board can be seen in MS-10pic3:
     
     
    The completed MIDI control panel installation is shown in MS-10pic4:
     
     
    8)  Determine the place that the MIDI input DIN jack will be mounted.  A good place to mount it is on the back panel on the far right side away from the power cord.  There is a lot of room behind the rear panel of the MS-10,  so you are not limited in your choice for suitable DIN jack mounting locations,  but be careful to keep all MIDIJACK wires and connections away from the high voltage power components.  The way to make this look like original Korg factory equipment is to mount the DIN jack outside the metal panel instead of inside the panel as in a normal MIDIJACK installation.  To do this,  mark one of the two wires (#9 orange or #10 gray) at the terminals of the DIN jack with a marking pen or tape to remember the polarity then desolder both wires.  Use the paper drilling template labeled DIN Jack Mounting to properly mark and drill the holes as shown in MS-10pic5:
     
     
    It is advisable to use a chassis punch to make the hole for the DIN jack.  Remember that the DIN jack is to be mounted with the smaller 4-40 hardware size rather than the larger 6-32 size that secures the main board.  Drill two holes for the screws then drill a slightly larger hole in the center to act as a pilot hole for the chassis punch.  Use the chassis punch to cut the hole and be sure that the wrench is turning the tool from inside the MS-10,  not outside,  so the cutting edge is coming from the outside.  This will ensure that the outer edge is perfectly smooth.  The properly cut mounting holes may be seen in MS-10pic6:
     
     
    The MIDIJACK hardware packet contains both long and short 4-40 screws for the DIN jack.  Use the two short ones for installation on a thin metal panel such as the MS-10.  When all three holes are perfect,  put the DIN jack in place outside the chassis and secure with the two screws from the outside,  and two split washers and two 4-40 nuts on the inside and tighten with a small Phillips screwdriver from the outside and needlenose pliers from the inside.  These nuts should be very tight.  By using the Synhouse paper drilling template,  a center punch to start the drill,  and a chassis punch,  your MS-10 will look like it had MIDI when it came from the factory,  as in MS-10pic7:
     
     
    Reconnect the wires to the DIN jack at this time.

    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:
     

     
    The proper +15v signal can be obtained from the back side of the circuit board in the MS-10.  While looking at the circuit board so that the Korg factory writing can be read upright,  look to the lower far right corner and solder the MIDIJACK #2 red wire to the point shown in MS-10pic9:
     
     
    11)  Locate the factory Korg input jack in the far upper left corner of the jack panel.  It is in the VOLTAGE CONTROLLED OSCILLATOR section and is labeled FREQ -3V~+3V OCT/VOLT.  Look at the back of the jack and find the blue Korg factory wire.  It is soldered to the terminal which connects to the tip of an inserted plug.  Remove the wire from the solder terminal by desoldering it.  Solder the MIDIJACK #3 blue wire to the now-empty isolated CV terminal.  This connection can be seen in MS-10pic10:
     
     
    12)  Solder the MIDIJACK #4 white wire to the now-disconnected factory Korg wire which is also blue.  Carefully wrap the solder joint with electrical insulating tape.

    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:
     

     
    14)  The MIDIJACK #5 yellow wire,  #6 green wire,  and #8 violet wire (unless it is used for a special function as described in the Advanced Installation Manual) are not required for adding MIDI to the Korg MS-10,  but it is a good idea not to permanently cut these wires off,  as an alternate installation method may become useful later.  It is best to wrap the ends of these unused wires with electrical insulating tape and bundle them with the other wires when finishing the installation.

    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:
     

     
    When you needed MIDI control,  you could patch them any way you like.  This configuration would actually make for an easier installation than the intended method which bypasses the keyboard automatically.
     
     

    Copyright © 3/19/2001 Synhouse Multimedia Corporation