Micromoog Analog User Modifications

Analog User Modifications:

Moog MicroMoog

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FREE Do It Yourself Special: FREE plans to add MIDI capability to the Moog Micromoog with the Synhouse Moogiestyle MIDIJACK!

The following plans describe a method of adding MIDI capability to the Moog Micromoog analog synthesizer with the Synhouse Moogiestyle MIDIJACK. This will allow the Moog Micromoog to be used as a MIDI analog monosynth. Some drilling is required. The micro size and black color of the MIDI button are such a perfect match for the Micromoog that it makes it look as if it came from the factory with the MIDI interface. The installation of the MIDIJACK in a Micromoog is one of the easiest modifications of all. In fact, with the MIDIJACK, it is possible to convert the Micromoog to MIDI without even removing a single circuit board from the instrument! The correct analog I/O signals are easy to find and connect to the MIDIJACK. Like many older American synthesizers, the Moog Micromoog has panel-mounted CV/gate jacks with solder lug terminals and the MIDIJACK wires can simply be soldered right inside the panel and the whole MIDI conversion job can be done in one hour. The 1/4" jacks do not even need to be unscrewed from the back panel. They may be left in place and soldered right on the spot. This modification reroutes the local keyboard signals through the computer-controlled analog switching matrix of the MIDIJACK by extracting the signal and inserting the users' choice of local keyboard control or MIDI. 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. 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:

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 inputs (highly recommended), you will need 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 3/32" 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. If you choose to mount the DIN jack in the soft plastic portion of the Micromoog 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 Moog Micromoog 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 Moog Micromoog. 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) Open the case and turn the synthesizer upside down and shake out any dust and debris that may have accumulated inside the instrument over the years.

5) Determine the place where the MIDIJACK circuit board will be mounted and test fit the board into its correct place inside the
case. The mounting location is up to you. The installation done for this article shows the board mounted above the rear jackpanel, hidden with the button facing down, which was fairly time-consuming, but created a nearly invisible MIDI installation. Mark the correct mounting holes on the panel with a pencil, marker, or needle using the paper drilling template provided with the MIDIJACK hardware packet. A photo called MM-pic1 shows the paper drilling template in place:

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 MM-pic2 shows the location of the newly cut mounting holes:

6) 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 large enough so a Synhouse Pocket Screwdriver can fit through the panel for periodic adjustment.

7) Determine the place that the MIDI input DIN jack will be mounted. One place is on the rear jackpanel 1" below the audio and modulation input jacks. The way to make this look like original Moog factory equipment is to mount the DIN jack inside the metal panel after marking the bare metal edges of the hole with a black Sharpie permanent ink marking pen to match the black finish of the original metal chassis. Use the paper template to mark the correct spots to drill and cut as shown in MM-pic3:

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 Micromoog, not outside, so the cutting edge is coming from the outside. This will ensure that the outer edge is perfectly smooth. If you do it this way, you may need to temporarily unscrew the keyboard and use a long socket extension to be able to turn the punch tool, as it is so close to the base. The properly cut mounting holes may be seen in MM-pic4:

The MIDIJACK hardware packet contains both long and short 4-40 screws for the DIN jack. Use the two long ones for installation on a thick aluminum panel such as the Micromoog. When all three holes are perfect, put the DIN jack in place inside the chassis and secure with the two screws from the outside, and the four split washers and two 4-40 nuts on the inside against the back of the DIN jack and tighten with a small Phillips screwdriver from the outside and the needlenose pliers from the inside. These should be very tight as they are going onto the metal surface of the DIN jack. If done cleanly and correctly by using the Synhouse paper drilling template, a center punch to start the drill, and a chassis punch, your Micromoog will look like it had MIDI when it came from the factory, perfect like the one shown in MM-pic5:

8) The MIDIJACK #1 black and #2 red wires must be soldered in place to get the ground and power for the MIDIJACK. If you are capable of doing this modification, it will be very easy to find the +15V and ground sources that you must connect these wires to, but suggested contact points are on the Micromoog power supply board as shown in MM-pic6:

The MIDIJACK #1 black wire must be soldered to the anode end of the diode CR105 (the end AWAY from the little band painted on it) to get the ground for the MIDIJACK. The MIDIJACK #2 red wire must be soldered to the positive side of capacitor C105 to get the power for the MIDIJACK. These connections may be seen clearly in the closeup photo MM-pic7:

Solder the two wires in place. An ultra-clean installer may prefer to cut all wires to the perfect length, but other users may prefer to save time by using the precut, stripped, and tinned wires at their standard lengths and there is no electrical reason not to. It is just a matter of preference and after the job is done and the Micromoog is put back into service, who will care?

9) The CV connection must be made next. Locate the CV input jack labeled OSC. At the rear of the jack, the top terminal has a wire soldered to it which is white with green stripes. Desolder this wire. Solder the MIDIJACK #3 blue wire to empty terminal as seen in MM-pic8:

Solder the MIDIJACK #4 white wire to the now-disconnected wire which is white with green stripes and insulate the solder joint with electrical insulating tape as seen in MM-pic9:

10) Moog synthesizers generally do not disconnect the keyboard from the trigger circuit with a switched jack as they should. For this reason, the trigger jacks will still trigger the envelope generator even with the MIDI activated. The MIDIJACK S-trigger wire must then be connected in parallel with the existing trigger wire with the addition of a safety diode to prevent short circuiting. The MIDIJACK #7 brown wire (S-trigger output, unswitched) must then be connected in parallel with the existing trigger wire, using a small signal diode 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 orange wire which is going to the back of the S-trigger input jack labeled S-TRIG 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 S-Trigger OUT wire soldered to it. There will now be a factory wire AND a diode connected to this terminal of the jack, as shown in MM-pic10:

11) The MIDIJACK #5 yellow wire and #6 green wire are not required for for adding MIDI to an S-Trigger Moog such as a Micromoog, 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.

12) Now that all connections have been made, the MIDIJACK board, DIN jack, and all connections should look as shown in MM-pic11:

The hidden MIDI control panel done here can be seen in MM-pic12:

13) It is a good idea to cut short pieces of electrical insulating tape and use them to secure the MIDIJACK wires to the inside of the chassis so they will not rattle and break loose inside the case once the instrument is returned to service. The MIDIJACK hardware
packet contains nylon cable ties which can be used to tie the MIDIJACK wires to the original Micromoog wire bundles.

14) Carefully examine all soldered connections for possible short circuits before closing the instrument.

15) Close chassis and replace the screws.

16) Test and calibrate using the procedures described in the Moogiestyle MIDIJACK Quick Installation Manual. For calibrating the MIDIJACK on a Micromoog, please read question 6 from the Analog User Answer Forum page:

Question 6: I have a MIDIJACK MIDI interface installed in my Micromoog and it never plays in tune. The intonation of the keyboard is always bad. What's wrong?

Answer: The Micromoog never played in tune with anything except its' own keyboard. Controlling externally via CV/gate jacks always caused the notes to be out of tune whether it was 25 years ago from a Minimoog or more recently with some sort of MIDI controller type of device. It has been said to be not 1 volt per octave, but rather about .9 volts per octave due to some design error. This is no longer a problem. Do not underestimate the versatility of the MIDIJACK. It is all hardware. If your Micromoog has the problem of being .9v/octave instead of 1v/octave, it can be corrected with a quick adjustment on the MIDIJACK. Play a few notes on the Micromoog through MIDI. If the notes are all sharp as you go up, like the whole keyboard has steps that are too far apart, then it is less than 1v/octave.

The solution: The MIDIJACK has a scale adjustment trimmer that affects the musical intonation of the analog synthesizer while it is under MIDI control. It is less than one inch away from the MIDI function button and may be adjusted by inserting a small flatblade screwdriver into the control panel opening. A Synhouse Pocket Screwdriver fits perfectly. The scale adjustment trimmer may be set by ear if the Analog User has a good sense of pitch. A MIDI controller keyboard should be connected with a MIDI cable to the MIDIJACK and the audio output of the Micromoog to a sound system for monitoring. The MIDIJACK should be in MIDI On Mode and set to the same MIDI channel as the MIDI controller keyboard. While playing alternating notes on the MIDI controller keyboard that are an octave apart, the user can turn the scale adjustment trimmer very slowly until the proper one-octave interval is heard and the entire keyboard plays in tune. It may be easiest to hear the tones clearly by adjusting the Micromoog so that the filter is open with the frequency set to maximum, the emphasis set to minimum, and the envelope generators set to sustain, without any vibrato on the oscillators. An extra help would be to use a MIDI synthesizer or sample playback keyboard as the MIDI controller and listen to its sound output as a reference tone to match the Micromoogs' intonation while adjustments are being made. A low note may be played on the MIDI keyboard while the Micromoogs' master tuning knob is adjusted to bring the two sound sources into tune. Next, play higher octave intervals of that note, and slowly turn the MIDIJACK scale adjustment trimmer until the entire keyboard plays in tune. For the Micromoog to work properly, the trimmer will have to be turned about 10% down, or counterclockwise, from the Synhouse factory 1v/octave setting. With this altered setting, the MIDIJACK should be putting out MIDI notes 0-127 at a scaling interval of .9v/octave. You can shrink or stretch your scaling from 0v/octave (not too musical) to approximately 1.2v/octave. Actually more than that, you could turn it all the way up to 2v/octave but the MIDI notes above 64 would be clipped and all the same pitch. The MIDIJACK is designed this way because most old synthesizers are out of calibration in one way or another and this is one way to try to bring them back into adjustment. Additionally, it allows the MIDIJACK to work in instruments that have exponential oscillators other than 1v/octave, such as EML (Electrocomp 101 and others) and EMS (Synthi AKS and VCS-3). Analog calibration should only be performed occasionally, as overuse of the scale adjustment trimmer may cause excessive wear and premature failure of the part.

17) It is probably a good idea not to use the Micromoog built-in local keyboard or oscillator CV and S-Trigger input jacks while MIDI is activated or vice versa.

18) This installation can be completed in approximately one hour, depending on how you mount the MIDIJACK board.

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