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The DMX Files

Information, accessories and repairs for the
Oberheim DMX Drum Machine

Latest update: 2024-05-10

Photo of DMX  
Promenade Screenshot Promenade software for Windows is now available. Use with a MIDI connection to the Oberheim Prommer for reading and programming EPROMs. Can also be used without a Prommer to visualize and organize drum machine audio samples.
Free download! Give it a try today.
Switch body A switch cleaning tutorial shows how to renew those intermittent buttons on your DX or DMX.


I made a new page describing how to repair a common problem with DX and DMX pushbutton switches. The main contact spring can get bent out of shape and no longer make any contact with the lower contact wire. See this link
Well, Zilog says they are discontinuing the manufacture of Z80 CPU chips. This is not good news, and I will have to start conserving my supply wherever possible. Starting now, I will not include a new Z80 with MRAM boards, as your original Z80 should work OK when transferred to the MRAM board.

For the time being, I will still include new Z80s with DX and DMX MIDI boards, as these use a higher clock speed, and I can't guarantee that your old Z80s will work at the higher speed.

On the other hand, if anyone would like to buy any used but tested Z80s pulled from working equipment, I have a good supply of these available for sale.

Due to inflation, I will be raising my basic price for repairs from $99 to $129, not including shipping costs. This also covers the cost of new large capacitors for DX and DMX power supplies, which I have begun replacing as needed, due to the age of the old electrolytic capacitors, and as preventative maintenance.

Postage rates will also be going up to meet my costs for shipping.

I finally received the new batch of metal jack plates. The new ones are slightly different, as the old style MIDI jacks were getting very expensive. I designed a new circuit board for mounting the new style of jack, and a new plate design to accomodate the circuit board. The side panel cutout now needs to be slightly different. Dimensions and instructions for the new cutout are here. The "MIDI In" and "MIDI Out" labels are now laser etched into the metal, so no more stickers are needed. The jack plates are anodized now, instead of painted. Also, the MIDI jacks are now rotated so the keying notch is at the top, instead of sideways.
Back orders are going out this week.
I have temporarily run out of the metal plates that MIDI jacks are mounted on for the DX and DMX MIDI upgrades. I'm working on getting new ones made, and will post an update here when they are ready. In the meantime, you can still order these MIDI upgrades if you are planning to put the jacks on the rear panel instead of the side and don't mind punching holes in the metal DX/DMX case. Or, you can order the kit now and I will ship the jack plates later.
Update: New DX MIDI boards are in and ready to ship!
I am currently all out of DX MIDI upgrade boards, but will be getting more around the beginning of March.
A note for all MKC-1 (MIDI keyboard interface) owners: A bug relating to MIDI Active Sensing has been uncovered (held notes cutting off too soon), and a fix is available. You will need to send me your MKC-1 board for reprogramming at no cost, other than postage.
Here's a nice documentary about Tom Oberheim on YouTube.
We're back! Finally settled in after the big move and now filling orders and handling repairs again.
We're moving! Electrongate will be shut down for a couple of weeks during the move, but should be open for business again in the first week of January, 2021. Our new home will be in California's Central Valley, about halfway between Los Angeles and San Francisco.
I have known for some time that Promenade would run in Linux or FreeBSD using the wine emulator, just for manipulating files. Today I plugged an E-mu midi1x1 Tab USB-to-MIDI interface into my Ubuntu Linux machine and verified that it works for communicating with the Prommer as well. If anyone using a Macintosh would like to help me out, you can see if Promenade will work with one of the many free Windows emulators for Mac, such as Wineskin Winery or Wine Bottler.
I posted a video showing the installation process for the DX MIDI upgrade.
The second batch of MRAM boards is in, and they are working! Back orders will be filled within a few days. Thanks for your patience, all those who have been waiting.
Bad news: The new MRAM board are in, but due to a dumb mistake on my part, do not work. I'll have to reorder them and wait a few more weeks for the corrected ones to arrive. My apologies to all who have been patiently waiting.
New MRAM board assemblies are finally on order and should arrive in mid-February.
I've run out of MRAM boards and will need some time to get a new batch built. Also, I'm planning on revising the design of the MKC-1, and that will be out of stock as well until I finish the new design and get some boards made.

I'm going to be moving my woodshop in the next month or two, so there may be a time when I run out of walnut panels until I get the new shop up and running. I still have a couple of sets of panels left, as of this writing.

Due to the increasing cost of materials, I'm raising the price for handmade DX, DMX and DSX walnut end panels from $20 to $25 each. I'll be building more panels this weekend.
The new DX MIDI boards are in, and I'll be shipping existing orders this week and next week. Now, I need to make some more walnut end panels, but I should be able to do that this weekend.
I placed an order today for more DX MIDI boards from the PCB fabricator. I expect to receive them in about three weeks, and complete final assembly and testing and have them ready to ship by the end of the month.
Due to an increase from my supplier, I had to raise the price of replacement DLR1414 display modules to $35.
I just finished a small batch of DX MIDI boards. Ready for shipment on Monday.
I posted some instructional YouTube videos about cleaning switches and replacing slide pots on an Oberheim DXa. Here, here and here.
Updated the installation instructions for the DMX MIDI board with new photos reflecting new version of board.
I completed the fabrication on a new batch of end panels and they are now ready for finishing.
I have run out of walnut panels for the time being. I hope to get a new batch started in a week or two.
By the way, I have quite a few used panels available, including several of the plastic DX panels. Used walnut panels are half price ($10 each) and plastic panels are available for free for as long as the supply lasts. Shipping is extra in both cases.
The new DMX MIDI boards are in, and with successful testing, they are ready to go!
After 11 years, I have decided to raise the price of the DMX MIDI Board, but for the extra money, you get:
  1. On-board lithium battery to replace the old, leak-prone NiCd battery.
  2. Optional MIDI Thru output (Select either MIDI Out or MIDI Thru, or add an optional third MIDI jack for both).
  3. Secure hold-downs for the the Electrongate MRAM board, in case you want to do away with batteries altogether.
New DMX MIDI boards have been ordered and should arrive in about two weeks. This is a new revision and includes some nice new features.
1) There is an option for a lithium memory backup battery on the MIDI board, eliminating the old NiCd battery which was prone to leakage and required periodic charging.
2) Mounting holes have been added to the board to securely support the MRAM board option which allows eliminating batteries completely.
3) Components to support an optional MIDI Through jack have been added.
Pricing TBD.
A potential hardware bug has been found in the DX MIDI board REV. 1.01 (Stretch version only). The symptom of the bug is a doubling of the recording and playback tempo when using the internal DX clock source.
I've already notified Stretch owners by email, but if your Stretch DX is showing this problem, it may be corrected by replacing the 74LS32 IC (U4) on the MIDI board with a 74HC32. I will be glad to send a new 74HC32 at no charge to owners of a DX Stretch with the Electrongate MIDI interface.
If your Stretch is not showing this symptom, no changes need to be made.
Added a pictorial showing how I make the walnut end panels sold with DMX and DX MIDI kits. See it here.
Added DSX ECOs (Engineering Change Orders) and revision 3.01 software operation guide to the OB Files page here.
Added DSX Service Manual to the OB Files page here.
Added DX factory sequence tape image here.
Added photos showing Prophet 5 installation for MKC-1 MIDI-Keyboard converter here.
Added DX Owner's manual (rev.1) and Stretch manuals here. (Thanks to Edward Chen for providing the scans!)
New details about the tap tempo version of the MCC-3 have been posted here.
At the request of Forat Electronics, the copyright holder of the original LinnDrum samples, I have removed the Linn samples that were previously available on this site. Sorry for the inconvenience, but you can still get programmed Linn EPROMs from Forat.
Related to the math error mentioned below, all the WAV file samples in the EPROM sound libraries have been updated with corrected versions.
Updated Promenade to correct a math error in conversion of bin to wav files. New version is 1.03.
Added a "reggae snare" sample to the DMX/DX samples page.
unfinished DMX MIDI jack plates
New DX/DMX MIDI jack plates, ready for painting.
The link I had for the DX User Manual on another web site was broken, so I posted a new cleaned-up copy of the manual here. This is the second edition of the manual, covering the DX with factory MIDI, as well as units with the Electrongate DX MIDI upgrade.
I added a new product page for the MKC-1, a MIDI to Keyboard Converter. This board can be used to add simple MIDI control to older Oberheim synths (OB-X, OB-SX, OB-Xa) and the SCI Prophet 5.
unfinished DMX end panels
New DX/DMX walnut end panels are here! In this photo, you can see them after sanding, before drilling the holes and routing the openings for MIDI jacks. The panels are sorted into three piles based on which side has the best appearance: left side, right side or two good sides.
Added Matrix-12 voice board OS images and moved all other ROM images to a new page.
Many people have asked me about replacement voice boards for the DMX. I'm glad to announce that I now have these available. The design is based on the original 1554 single-EPROM voice board with a few minor improvements. The basic sound playback circuitry is identical to the original, so the sound is the same.
Brand new 
The boards will work with the original 24-pin 2732 EPROMs, but the new board also supports 28-pin 2764 EPROMs with two 4K samples that can be selected by a switch, either directly attached, as shown here, or through the external control voltage connector.
sound select switch
Check it out!
The new professionally machined and silk screened cases for the MCC-3 are in! Check out photos and information here. PayPal ordering and further information coming soon.
I just uploaded a tutorial video on YouTube showing how to clean a volume fader on a DX or DMX.
Added a DSX test EPROM image..
Added schematics for the DXa.
Added a DX FAQ for frequently asked questions about the Oberheim DX drum machine.
Added DSX OS ROM images to the OB-Files page.
Added links to some OS ROM images in the OB-Files page.
Posted some Drumware and Digidrum samples here and here.
The 100th Electrongate DMX MIDI upgrade is ready to ship!
Removed non-working Google Friends link. Added some missing dates to older blog entries with the help of the WayBack Machine.
Added the DMX switch board parts layout drawing to the OB Files.
Promenade, a Windows application from Electrongate is now available for download or purchase on CD-ROM. Promenade is an interface program for the Oberheim Prommer, and supports data transfer, remote control of reading and programming EPROMs and has a nice visual interface.
Prommer owners, give it a try and let me know how it works for you.
Added patch descriptions to OB-Xa patchbook index page
Added Am6070 DACs to the products page here.
Added scans of all the ECOs I could find relating to the Oberheim Xpander here.
Added a schematic for the DMX memory expansion board to the OB-Files page.
I added a page comparing the DMX and DX.
If anyone sent me email on Friday (October 28), could you please re-send it? My mail server was down all afternoon and I may have lost some emails that were sent in the afternoon. Thanks!
The Stretch features on the new DX MIDI board work perfectly. The long ribbon cables that connect the Stretch to the DX main board, combined with the higher clock speed of the MIDI board Z-80, caused problems when installing the older DX MIDI upgrade in Stretch DXs. The new board is designed to eliminate the noise on the address and data lines that caused the problem. The redesign also moves the RAM chip that was previously moved to the Stretch board, back to the DX main board, for better battery backup reliability. The Stretch cables now plug into sockets on the MIDI board, rather than the DX main board.
Thanks to Jimmy Gillan for the loan of his Stretch DX for my testing!
The parts have arrived and DX MIDI kits are available again. The new board works great, and I will be building some more this weekend. I hope to test the Stretch features on the new board in the near future.
While waiting for DX MIDI parts, I did some work on Promenade, my Prommer interface program. The new version is almost ready for release and supports lots of neat new features, like saving and loading .BIN, .WAV and .HEX files with automatic conversion from WAV to BIN and vice versa. Drag and drop is now working, to make it easy to load sound files. Clicking on the waveform display will now play the selected sound through the PC speakers.

Watch this space for more news soon!

The PCBs for the new DX MIDI upgrade have been ordered and should be here next week.
I've been working an a new PCB layout for the DX MIDI upgrade, since I ran out of boards from the last batch and needed to correct some errors in the original design.
I have decided to eliminate the built-in MRAM option, for a few reasons.
  1. It was expensive and not many people were really interested in it.
  2. The lithium battery system in the DX really works pretty well as it is, especially compared with the NiCd battery system in the DMX.
  3. It made the MIDI upgrade PCB layout more difficult.
Adding MRAM to the DX is still an option by installing a MRAM board on top of the MIDI upgrade, or directly into a factory stock DX.
I am also adding a Stretch interface option to the DX MIDI board that should eliminate a couple of problems with the Stretch that turned up when people installed the old DX MIDI board in their DX Stretch units.
Watch for the new DX MIDI board in the products section, coming soon!
Yay! I found a source for the Am6070 DAC ICs that are used in the DMX and DX and bought a bunch of them, so I have them in stock now. That means that I will have a few more 1554 (single EPROM) and cymbal #1 voice boards available for sale.
New in the products section: The UniTrigger (CV-to-MIDI box) and MIDI Clock Converter (MIDI clock to clock pulse gadget). Check them out!
New in the DMX EPROM images department, Beat Kick and Beat Snare samples have been added.
I just added a new version of the addendum to the DMX Owner's Manual for revision 4 firmware (MIDI). This is a 17 page document with details about the new edit parameters and describes lots of stuff you may not have known your DMX was capable of.

For example, did you know that you can use "tap tempo" to set the tempo on the DMX? In the document, it's referred to as "Cue Tempo," but it's basically the same thing.

And did you know that you can save and load the sequences and songs in the DMX over MIDI?

I encourage current owners of MIDI DMXs (including those with the Electrongate MIDI Upgrade) to download this PDF document and find out what the DMX is capable of!
I added a link for Google friends at the bottom of this page.
DX MIDI News: The DX MIDI upgrade is now available with built-in Magnetic RAM, so you can combine two upgrades in one. The instability problem has been fixed and after several days of continuous testing, I've decided it's ready to release. Place your order here.
MKC-1 News: The glitch in the MKC-1 is fixed. Everything is now working perfectly with the OB-X. In theory, it should also work as well in the OB-SX, OB-Xa and OB-8, since all of these use the same keyboard interface method. I'm pretty sure the MKC-1 will also work with Oberheim TVS and FVS systems.
The first MKC-1 prototype is up and running. I'm testing it on an OB-X at the moment (thanks to B.C. who loaned me his). It seems to be working very well with the OB-X, with only a minor glitch in the top octave of the keyboard, which I should be able to fix without too much trouble. The keyboard pass-through is working fine, and MIDI in and MIDI out are both working as well. I still need to test the local control on/off and onmi-off functions, but it's looking good.
The price for the MKC-1 will be $129, and once I get a few more built and tested, I will put an ordering link up on the products page.
My first tests with the DSX led me to discover that the DSX firmware version I have (3.04) doesn't support an external keyboard as described in the owners manual. It looks like I will need to work on a modified version of the DSX firmware in order to make the MKC-1 work with the DSX, and that will take some time.
Ten MRAM boards are complete and tested. I made a small modification to this batch, which I think will result in improved reliability.
DX MIDI kits are now sold out. Expect 1-2 weeks delay.
A new batch of MRAM boards is almost ready.
DMX MIDI kits are sold out. Expect 3-4 weeks delay if you order one.
Update: I just ordered printed circuit boards for the new MKC-1 (MIDI to keyboard matrix converter), which will emulate an external keyboard in the Oberheim DSX, as well as adding MIDI keyboard control to any of the older non-velocity Oberheim synths (OB-8, OB-Xa, OB-SX, OB-X and possibly even the SEM based systems. I expect boards to arrive in about a week, and if all goes well, testing will begin shortly after that. The firmware is written, just awaiting hardware for testing.
MRAM News: I have parts for more MRAM boards now and just need to finish assembling and testing them. Maybe this week...
A new batch of walnut end panels have arrived. I recently finished building more DMX MIDI kits and still have some DX MIDI kits in stock. I'm currently building more Magnetic RAM boards.
I did a custom modification of a DMX last week which added a Sync24 (DIN sync) output to the DMX. I tested it with a Roland TR-606 and it worked pretty well. I'm thinking of adding this as an option on future DMX MIDI upgrades, or perhaps as a stand-alone mod.
Oberheim Prommer owners: I'm working a Windows application that will let you transfer data files to and from your Prommer so you can program EPROMs. All you need is a Prommer, a MIDI interface for your computer and two MIDI cables. I should be releasing this program soon. If anyone is interested in testing a preliminary copy, let me know.
There is a new version of firmware for the DX MIDI kit which fixes a problem in the Stretch DX. This version will ship with all future DX MIDI kits, but current owners do not need to upgrade unless they have a Stretch DX. Thanks to Bruce Forat for helping me find and fix this problem!
Now accepting DX and DMX repairs again. Contact Paul to arrange shipment of your machine to Coalinga, California.
Basic overhaul price for either machine is $129, which includes switch cleaning, new battery and minor repairs as needed. Return shipping via UPS is extra. Some repairs may require specialized parts or extra labor at additional cost.
Electrongate is moving! We are temporarily unable to accept machines for repair. This situation should change within a couple of weeks. Please do not send any shipments to the old address. Please contact Paul White to arrange shipment of your DMX for repairs or upgrades.
I am withdrawing the MRAM option for the DX MIDI board due to some reliability issues. The basic DX MIDI upgrade is working fine, but the PCB layout of the MRAM section turns out to have some problems. Sorry about that.
DX MIDI upgrade news:
I shipped the first five DX MIDI upgrade kits this morning! More should be ready to go out tomorrow.
Now in the accessories product page: DSX ribbon cables to connect your DSX sequencer to your classic Oberheim synthesizer.
Work is progressing on a DX MIDI upgrade. Watch this space for an announcement soon!
My stock of 1554 DMX voice cards is starting to run very low, so I am designing a replacement voice card that will sound just like the original (using the same filter circuit), but will have more options for different EPROM sizes and be easier for the user to configure. Stay tuned for more info.
I just found out that the DMX Files were mentioned in this article in The Guardian, written by David McNamee. Thanks, David!
The Magnetic RAM upgrade has now been successfully tested and is now available for the Oberheim OB-Xa synthesizer! Thanks to German Hernandez for his assistance,
The Magnetic RAM upgrade has been successfully tested and is now available for the Oberheim OB-8 synthesizer, as well as all versions of the DMX and DX drum machines! Check the products page for ordering information.
New! Magnetic RAM upgrade for Oberheim Z-80 based products (DMX, DX, OB-8, OB-Xa, OB-X, DSX). The circuit boards are in, and the DMX version is tested and working correctly!
This upgrade replaces the battery RAM with a new magnetic RAM technology -- no more battery replacements, no more battery leakage, no more memory loss due to dead batteries. A small circuit board plugs into the Z-80 socket and the Z-80 is moved to the Magnetic RAM board. The old RAM ICs and battery are removed. That's it! No soldering required. This board will work with all versions of the DMX, including the MIDI version.

The MRAM board has been successfully tested on three versions of the DMX, the DX, DXa and now the OB-Xa and OB-8.
Sequential Circuit Drumtraks EPROM images now available here.
New samples on the DMX EPROM image page: Electric Kick, Electric Snare 3, Long Hi Hat, Long Noise and Scratch.
Visit the new Friends of Electrongate page! If any of my customers or other friends would like to be added to the list, just drop me an email.
Due to the battery price increase, the cost for a DMX tuneup is going up to $89.
Batteries! We now have replacement lithium batteries with solder pins as used in the Oberheim DX, OB-X, OB-Xa and OB-8.
Due to a price increase from my supplier, the cost of replacement DMX/DSX batteries has gone up.
Check out the new product page -- you can use PayPal to buy cool DMX accessories! Click the link at the top of the page.
New Electrongate products, now in production -- photos coming soon:
  • DMX Trigger Box DTB-8 -- A rack-mount interface that allows playing the DMX with external trigger pads such as those made by Roland or Simmons (not included). The DTB-8 features eight 1/4 inch input jacks on the front panel, each with an LED trigger indicator. A custom cable connects from the rear panel to the Molex trigger connector on your DMX. Trigger sensitivity is adjustable by means of a trim pot for each individual channel. Powered by an internal 120/240V AC power supply. $279
  • DMX Trigger Box DTB-10 -- like the DTB-8, but with the addition of two multi-trigger inputs that allow triggering any combination of drums with a single trigger pad. The combinations are set by DIP switches. $299
  • UniTrigger UT-1 -- A simple MIDI trigger box that accepts a single voltage or variable resistance trigger input and produces MIDI note-on/note-off output. A multi-turn pot sets the base MIDI note number, and a 0 to +5 volt control voltage (CV) input allows setting the MIDI pitch at 1 volt per octave. Features LED power and trigger indicators and a pitch select knob on the front panel. The rear panel has a DC input jack, MIDI In and MIDI Out jacks, 1/4 inch CV and Trigger Input jacks. $129
  • Click Box CB-1 -- Give your drummer a click track to keep time with your MIDI sequences. The CB-1 is like a synthesizer with only one sound -- any MIDI note-on received on the selected MIDI channel produces a click. The tone of the click is determined by the note-on velocity, so you can emphasize the down beat. Just add a track to your MIDI sequence with a note every quarter note and assign it to the CB-1 MIDI channel. Direct output to headphones is through a 1/4 inch stereo jack, or send the output to a mixer or amp for more volume. An analog volume control sets the level. An LED on the front panel blinks with each click, and the rear panel features MIDI In, MIDI Thru, DC power in and the headphone output jack. $99
THUMBSCREWS! We now have a supply of those cool thumbscrews for the front cover of your DMX or DX. These make it easy to open your drum machine to change EPROMs or voice cards without using any tools. A set of two thumbscrews is available for $5.00, including postage to anywhere in the USA. Click here to order.
KNOBS! We now have replacement volume slider knobs for the DMX available. These are exact replacements, newly manufactured by Rogan, the company that made the original knobs for Oberheim. The same knobs are also used on the Oberheim DX (and Stretch). Click here to order.
Added link to panel cutout diagram for end panel modification on the DMX MIDI installation instruction page
Just added: Oberheim DX schematics and part layout drawings here.
Started blog on this page.
DMX picture is colorized, "In color" added to page title.
DMX Files goes online with a black & white image at the top of the page.

Technical information for the Oberheim DMX drum machine

This information is provided as a public service by Electrongate.

DMX Resources

Do-It-Yourself Resources

These documents are primarily intended to provide guidance for those wishing to modify Oberheim DMX voice cards. A basic knowledge of electronics, circuit board assembly procedures, parts handling and soldering is assumed. If the reader is not comfortable making any of these changes personally, a competent electronic technician should be consulted. These documents are believed to be correct to the best of our knowledge, but Electrongate will not be responsible for any damages or injury caused by information provided herein. The reader should proceed with due caution, and any modifications are made at the reader's own risk.

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