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The following modification info is found in Music Machine, unless specified otherwise. If you have any other tricks and tips in using Matrix-12, please email to me. I will put them here ASAP. Thanks!

Individual Audio Outputs

From Mon Jul 21 15:08:51 1997
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for <>; Mon, 21 Jul 1997 15:08:49 -0700 (PDT)
21 Jul 97 18:02:58 -0500
21 Jul 97 14:36:23 -0500
Date: Mon, 21 Jul 1997 11:28:15 -0700 (PDT)
From: (Keith Sterling)
Subject: XPAND: M12 separate outs

>Hi all!
>Could you help me to find how to put 12 outs for my Matrix12?
>I think I only need to connect the jacks to some point...
>Thanks a lot,
>Josue Arias.

The connector you are looking for is on the left-rear of the voice boards.
According to my M-12 schematics the pinout is:

pin connection

9 V1
11 V2
13 V3
14 V4
12 V5
10 V6

You can use a 14 pin dual inline IDC connector and ribbon cable to
distribute the voices to rear panel 1/4 inch jacks.


Individual Audio Inputs

The following Xpander™ Xpansion Documents are not from Music Machine. But I can't recall where they are from. If you know, please tell me. Thanks!

Letter 1
Letter 2
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Schematics 1
Schematics 2

Memory Expansion

Eric Rehl reports: "Since I don't carry a computer around with me when I go to different studios, it became important to me to have a lot more patches available inside the Matrix-12 than the 100 singles and 100 multis we are all used to. So pay attention, everyone, I have a solution which I would like to share.

"My friend Joe Weitekamp, at dBm Electronics here in New York, has devised a modification that quadruples RAM storage in the Matrix-12! It will also hold patches in the edit buffer and will let you transfer them between the four banks of available storage space. He used a momentary push button switch which cycles between the banks, and installed a set of four LEDs to let you know which bank you are in. You can also use all the normal patch storage schemes now available (cassette and MIDI). It cost me $450, but could be different now; contact him for details. Two caveats: it hasn't been tried yet on an Xpander (although I called and asked him about that, and he said he felt it would be easily accomplished) and he wasn't sure whether he would offer it as a kit or require that the instrument be sent to NYC for him to do it himself.

Joe does other custom work that may be of interest, including an amazing MIDI mod for the Memorymoog. He's very busy, so please don't call just to chat. If you're interested in his work, call or write: Joe Weitekamp, dBm Electronics, 124 W. 19th St. New York, NY 10011 ph. (212) 645-2626

DISCLAIMER: Neither I nor the XUG will take responsibility for any non-factory alteration of an Xpander or Matrix-12. Joe's reputation is good, and I'm thinking of letting him hotrod one or both of my Xpanders, but before you go sending your gear off to him, remember: you'll void your warranty, and may make it difficult for other Oberheim repair places to service your unit. Talk to Joe about the ups and downs of this operation before you make a decision, and if you decide to it, let us know how it turns out!

Originally from Xpansions ! The Newsletter of the Xpander Users' Group Issue 8 Summer Solstice 1991

Other Modifications

From Sat May 31 07:13:17 1997
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31 May 97 10:08:58 -0500
27 May 97 13:02:24 -0500
Date: Tue, 27 May 1997 09:56:45 -0700 (PDT)
From: (Keith Sterling)
Subject: Re: Anyone here?
X-MIME-Autoconverted: from quoted-printable to 8bit by id HAA24014

>Hi Keith,
>I´m very interested in modify my matrix12. I want to add sep outs and
>What mods do you have done?
>tell us!

O.K., here goes:

replaced oberheim's horrendous keyboard assembly, which belongs in the lowest Casio, with a Kurzweil K2000 keyboard assembly. Both units use the same encoding scheme so this was easy. I built a small pcb to adapt the K2000 assembly to the M-12 keyboard connector. The K2000 keyboard assembly was a second choice to a Roland but at $165 factory direct was much less expensive.

Installed the guts of a Yamaha MCS-2 (I think thats what it was called) controller in the M-12. Oberheim never perfected their lever controllers. No matter how much I cleaned the pots the M-12 would spit out reams of PB=0,PB=1, PB=0, PB=1 data whenthe levers weren't being touched. This resulted in my midi sequences being padded with much useless data that then would clog the midi port and cause timing inconsistencies. The MCS-2 provides 2 wonderfully linear very clean wheels which I mounted in the LEVERS bay. As a bonus it supplies 4 pedal outs, which I routed to back panel 1/4 connectors. Of course the MIDI in and out were re-routed from the back panel of the M-12 through the MCS.

Because the MCS board was mounted directly over the power supply unit I decided to add a fan. One of those 12 volt 3 inch units mounted directly under the cassette jacks. Because I use the M-12 in the studio as well as live I added a switch to run the fan slo (fan runs quiet at 7 volts) or fast (fan runs loud at 12 volts). When in slo mode the fan is barely audible but keeps the M-12 happily cool. The SPEED toggle switch is right beside the fan.

Well, I have to go to work now but I will continue this story:

Voice 6 has a Moog LPVCF
Mem Protect button erases all memory
giant multi connector on back
replace many op-amps with Analog Devices chips
much much more.

The reason I have done these mods is to fully realize the vision that the guys at Oberheim had of their ultimate synthesizer. They got 90% of the way there. I've gone the last 10%.

btw, if you want to add individual voices to your M-12 the connector is at the upper left hand corner of the voice board. You should be able to find out the wiring very easily with a probe and a set of headphones. Good Luck!