MIDIbox Chaos Matrix User manual
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Chaos Matrix
Introduction
Chaos Matrix is a programmer for an Oberheim Matrix 1000 analog synthesizer built by Patrick
Manderson. It's capable of manipulating all 126 voice parameters including 10 programmable matrix
modulations buses, ramp generators, 5 point tracking generator, 3 five stage envelopes, 2 oscillators,
2 LFOs, and much more.
It features edit buffer synchronization for visual feedback and inspection of all Matrix 1000 voices
parameters, patch compare, patch init, advanced performance options for some parameters as well
as containing all 1000 original patch names. Seeing patch names instead of numbers alone, makes it
a lot easier to remember your favorites.
Chaos Matrix was completed in March 2010 after installing the MIDI Merger unit, and building a rear
panel with jacks power plug and switch. It was built with help from the MBHP (MidiBox Hardware
Project) using the MIOS operating system. It uses 1 DIN module, 1 AIN module, 1 DOUT module and 1
core with a PIC18F4620 microprocessor along with a custom application built with the C skeleton
interface. The internals of a MIDI-MAN MIDI Merger 2×2 were used to provide the 2 MIDI input
merging.
Forum announcement here: Choas MAtrix Announcement
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Video
Current Status (updated 20100301)
Software complete. Beta source code available on this post
How-To Build document still needs more content
Features
Almost all communication from the Chaos Matrix to the M1000 is made via MIDI system exclusive
messages. Non-registered parameter numbers were not implemented in the Matrix 1000 firmware
despite what the manual states. Some communication from the M1000 to the Chaos Matrix is
necessary however.
Real-Time Modulation Control
All button clicks and knob twists on the live panel send sysex voice parameter changes by default.
Oscillator 1 and 2 frequency is controlled by rotary encoders to improve tuning accuracy. The rest of
the knobs are potentiomenters. The pulse width potentiometers are dual purpose. In one mode, they
adjust the pulse width to a fixed duty cycle, in another mode, the same potentiometer adjust the
modulation depth of the pulse width controlled by LFO2. These two modes can be toggled by clicking
on the pulse waveform button. The sync button cycles through 4 sync modes, LFO waveform buttons
cycle through the 7 available waveforms. Oscillator click toggles click on/off as well as enabling the
noise waveform.
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Patch Initialization
Voice parameters can be initialized to a default setting. Voice edit initialization is a good starting point
to begin creating a new patch from scratch. The initialized parameters are sent to the M1000 so the
display on the Chaos Matrix matches what is heard on the Oberheim.
Edit Buffer Synchronization
When selecting a new patch, the edit buffer is requested from the M1000 and processed by the Chaos
Matrix, updating the status of all LEDs and parameters in the soft panel. When the edit buffer is
received, you can inspect the matrix modulation, ramps and tracking generator parameters for all the
patches in the M1000. When you tweak any of the live panel controls, the original value as well as the
newly adjusted value is displayed. This feature requires additional MIDI cables to route the MIDI out of
the M1000 back to the MIDI in of the Chaos Matrix.
Patch Compare
When editing patches, the patch compare feature lets you compare your current edit to the original
patch.
Saving Voices
In the edit menu, select the 2nd page and select a patch location (0-199) to save your current patch.
Voice Names
The M1000 doesn't handle voice names like the Matrix 6/6R, they are simply ignored and never
stored. However, each and every patch name (published when the M1000 was released) was
painstakingly included in the Chaos Matrix firmware and is displayed while browsing patches. Seeing
patch names on the LCD instead of numbers alone, makes it a lot easier to remember your favorites.
Enhanced Performance Options
Due to the M1000 processor lag when adjusting parameters by sysex, the filter frequency control can
optionally send continuous controller messages which are then handled by a matrix modulation bus.
When this feature is enabled, the first free bus is used to route lever 3 (breath controller) to filter
frequency. The frequency knob will then send continuous controller messages on the current MIDI
channel.
History
The project started in 2006 with a bold design: build a voice programmer for an Oberheim Matrix
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1000 with a dedicated control for every parameter.
Unfortunately there was a physical limit to the number of analog and digital inputs I could use with
one core. So I compromised by layering groups together, like the DCO, LFO and ENV controls with
select buttons.
The prototype, containing all the surface controls was built and mounted in a pair of cardboard boxes.
90% of the software was completed and all the panel controls worked as designed.
The project didn't go much beyond that for a few reasons.
The cost of manufacturing the aluminum panel, along with the engraving for each and every
control (104) exceeded $450. Way too much money than I was willing to spend.
The aesthetics of all the controls on a 6u rack mountable panel was rather unattractive and and
difficult to read. I also realized for a lot of controls, I rarely used them (ramps, tracking
parameters, modulation switches). These were taking up valuable space on the panel and
getting everything arranged neatly on the panel was difficult.
I ran out of flash storage on the PIC18F452 microprocessor and had a lot more features to code
for the LCD panel and the matrix modulation parameters. This was later resolved by getting
another PIC with more storage.
And finally, the compromises I made layering some of the most important parameters made
sound programming non intuitive.
After all my hard work, I didn't want to invest any more money and time on something that was ugly
and costly and didn't work as intended. For the next few years the prototype sat in my office.
Occasionally I would turn it on and play it a while. Eventually I got tired of looking at an incomplete
project and decided to give it another shot. This time, sticking to the basics… keeping it simple.
Panel Design
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The redesign of the panel began with inspiration from a few classic analog synths: The panel to the
Oberheim OBX, Roland Jupiter 8 and Jupiter 6. I liked how simple the two rows of controls were laid
out on the Jupiter 8 and how easy it was to see the flow of synth parameters. I knew that the Chaos
Matrix would have to have no more than two rows of controls and they would have to fit in 24 inches
of the “Live Panel” and the rest of the parameters would be menu driven from the “Soft Panel”.
FrontPanel Express file is attached to this post. Please note: I mistakenly didn't engrave the OSC-LFO
pots with the negative, center and positive markings. The software currently treats those parameters
in the positive ranges only. If you build one of these, let me know if I can assist in updating the
firmware to accommodate both positive and negative. The cost of the panel through FrontPanel
Express was approximately $175 with shipping in the USA.
Live Panel
The most important parameters would have a dedicated control here. Note: the Matrix 1000 actually
has 3 envelopes. The 1st is almost always modulating the filter cutoff, the second envelope
modulated the main VCA and the 3rd was sometimes used to modulate the FM amount or the DCO
pitch. I decided the 3rd envelope would be accessed through the soft panel when tweaking the preset
patches.
Soft Panel
The rest of the parameters would have to be controlled from a menu driven interface using a 2×20
CLCD, 1 encoder and 8 buttons with LEDs.
LFO Section
2 LFOs, each with a Speed and Depth potentiometer, and a button to toggle 1 of 7 waveforms. The
last waveform “Sample Modulation” can further be edited on the soft panel with its rotary encoder.
The speed values are also indicated by blinking the LEDs on the waveform buttons. The slower the
LFO setting, the slower the blinking.
Oscillator Section
All the knobs on the Live panel are potentiometers except for DCO1 and DCO2 frequencies. The
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prototype originally used potentiometers but I found it difficult to dial in an exact frequency. I decided
to use detented encoders instead.
Pulse waveform can be enabled by toggling the pulse button and altering its shape with the “Width”
knob below it. Click the pulse button a 2nd time the button blinks and any adjustments to the “Width”
knob instead adjusts the pulse width modulation depth to LFO 2.
DCO2 Click/Noise button is a 3 state button allowing you to enable the noise wave without the need of
an additional button. When noise is enabled, the LED blinks.
The Sync button toggles the 4 oscillator sync modes.
Filter Section
The filter to envelope modulation modulates the cutoff frequency to envelope 1 by default when
editing preset patches. The Matrix 1000 firmware has a bug where envelope 1 sustain isn't handled
over its individual sysex parameter message. The work-around simply sends a complete packet of
parameters for the entire voice when sustain is adjusted.
Some of the parameters sent as system exclusive messages causes the Matrix 1000 to hang. If you're
playing notes and change some of the parameters, the notes will hold for a brief moment. Most of the
hanging is overcome by simply controlling the interval of messages being transmitted over MIDI for
each parameter. Most behave fine and the message can be sent at normal speed, but for others, the
transmit interval was reduced in order to compensate for the hanging.
The effect is ideal for slow pot movements, but for quick changes, a lot of the values in between the
1st and last movement are dropped. Despite this, the solution is better than having the Matrix 1000
hang.
Envelope Section
Instead of naming the envelopes “Envelope 1”, “Envelope 2” etc… I simply named them as they are
on the Oberheim OBX synthesizer. The filter envelope adjusts envelope 1 or 3 depending on which
patch is being edited.
Panel Construction
Some of the panel electronics, including the LCD module have to be mounted on the underside of the
panel. I used stripboards from FutureLec to mount the buttons together and applied Wilba's method of
attaching countersink machine screws with JB-Weld epoxy. The epoxy has to be applied in two steps
to ensure a good weld.
Step one: Simply dab a bit of the epoxy on the flat head of a machine screw and place the head down
on the aluminum panel (be sure to clean the panel surface thoroughly). Use a pair of clamps to
provide pressure between the screw and the panel. Wait at least 24 hours to allow the epoxy to cure.
Step two: Apply an additional amount of epoxy on the underside of the head of the counter-sunk
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screw and spread it over to the aluminum. You want to maximize the contact between the screw and
aluminum surface. Allow another 24 hours to cure.
How to build a Chaos Matrix
I realize some people may not want to build theirs using the same panel layout, same pots, buttons
encoders etc, but I'll document my construction as much as possible so it can be used as a reference
for those who want to build their own custom programmers for the Oberheim Matrix 1000. I would
categorize the construction difficulty as medium-advanced.
Hardware
1 PIC based core with a PIC18F4620
1 AIN, 1 DIN, 1 DOUT
MIDI merge. You can build one using the schematics found at ucapps.de. I simply extracted the
internals of an old MIDI-MAN 2×2 MIDI Merger I got off ebay. It uses power from the midi cable
and works fine.
1 2x20 CLCD with a 116 x 37 PCB and a 83 x 16.6 (or more) viewable area. If using a different
size, changes will have to be made on the front panel.
25 Alpha 10k linear potentiometers
3 Bournes detented encoders
16 Mountain Switch buttons with LEDs
1 small red LED T1 (.125“ Dia) 3mm
2 large stripboards (110 x 94mm) STPBRD1
5 small stripboards (94 x 53mm) STPBRD2
3 panel mount 5 pin common MIDI jacks from avishowtech
1 DC power jack
3 24 x 5 1/2 x 3/4 oak boards from local hardware store for the cabinet
8 L brackets with screws for the cabinet
2 pieces of trim stock for the cabinet
wood glue
wood stain
poly coat for the wood
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Building the Modules
Follow the standard instructions for building the 4 Midibox components and getting them connected
to the core. You will also have to build a cable to connect the core to the character LCD module. I
would highly recommend getting PCB kits from avishowtech.com instead of building and parting out
your own. The PCBs are of excellent quality.
PIC based core
AIN module
DIN module
DOUT module
wire up a LCD cable
The control surface components requires VSS and VDD power connections, I used one of the small
stripboards as a common power rail to connect these components to, by jumping VSS and VDD from
the PIC core. You may want to do it differently however.
Front Panel
All the pots can be mounted directly on the panel. Here is a simple guide on wiring pots.
AIN PIN wiring
0 LFO1 DEPTH
1 LFO1 SPEED
2 UNUSED (pin to ground)
3 OSC1 WAVE SHAPE
4 OSC1 LFO1 MOD
5 LFO2 DEPTH
6 OSC1 PLSE WIDTH
7 LFO2 SPEED
8 FREQ → ENV
9 RESONANCE
10 OSC2 LFO1 MOD
11 OSC2 PLSE WIDTH
12 FM → PRESSURE
13 FM AMOUNT
14 OSC2 WAVE SHAPE
15 FREQUENCY
16 FILTER RELEASE
17 FILTER SUSTAIN
18 ENV ATTACK
19 ENV SUSTAIN
20 ENV RELEASE
21 FILTER ATTACK
22 ENV DECAY
23 FILTER DECAY
24 DETUNE
25 OSC1←MIX→OSC2
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Finally, clamp the remaining unused AIN pins to ground.
The Mountain Switch buttons can be mounted on a small PCB. 2 of its pins are for the button, the
other two are for the LED.
DIN pin wiring for buttons and encoders
0 LFO2 WAVE
1 LFO1 WAVE
2 DCO1 ENCODER
3 DC01 ENCODER
4 OSC SYNC MODE
5 DCO1 PULSE
6 DCO1 WAVE
7 DCO1 CLICK
8 DCO2 ENCODER
9 DCO2 ENCODER
10 EDIT ENCODER
11 EDIT ENCODER
13 DCO2 CLICK
14 DCO2 WAVE
15 DCO2 PULSE
20 PAGE
21 MATRIX MODULATE
22 KEYBOARD
23 ENVELOPES
28 OSCILLATORS
29 FILTER
30 EDIT
31 PATCH SELECT
DOUT pin wiring for buttons
0 DCO2 CLICK
1 DCO2 WAVE
2 DCO2 PULSE
4 OSC SYNC MODE
5 DCO1 PULSE
6 DCO1 WAVE
7 DCO1 CLICK
8 ENVELOPES
9 KEYBOARD
10 MATRIX MODULATE
11 PAGE
16 PATCH SELECT
17 EDIT
18 OSCILLATORS
19 FILTER
21 LFO2 WAVE
22 LFO1 WAVE
23 MIDI ACTIVITY
Table of contents
