Oberheim OB-MX (1994)

Analog rackmount module synthesizer projected by Donald Buchla and not by Tom Oberheim as anyone would expect.

The Obmx module has been a total commercial flop on the market with a lot of lawsuit stories and legends. No support has ever been made for this machine soon forgot by the marketing machine.

RACKMOUNT 5 units. Main panel features a LCD 40 x 2 lines display, 32 knobs and 47 buttons.

Back panel terminal connectors:
- double main analog outputs
- individual out for each voice fitted (up to 12)
- MIDI interface
- separate outs can be used also as insert using a TRS cord

Front panel terminal connectors:
- headphones

 

VOICE subtractive synthesis machine features 2 voices polyphony for each voice card (You can install up to a maximum of 12 voices). A single voice is composed by 2 VCO oscillators based on CEM 3374 +1 white noise circuit.

VCO1 VCO2 Level mix yes yes Waveforms saw / tri / pulse saw / tri / pulse Variable width yes yes Tuning coarse +fine coarse +fine Hardsynch VOC1> VCO2 VOC2> VCO1 Ringmodulator VCO1>VCO2 - Pan image yes yes

t Voice boards are quite impossible to find on the market, better buy a model already expanded. It *SEEMS* that OBMX voice boards have been reverse-engineered by third-part but project is now officially dead because unprofitable.

FILTER multimode resonant VCF offers 2 models:

- VCF MM ( "Moog Minimoog")4 poles lowpass - VCF OB ( "Oberheim SEM") with 2 poles highpass, lowpass + bandpass.

The signal routed to VCO can be balanced between VCO1/ VCO2/ noise, in addition a Keytrack function changes the cutoff scaling factor cutoff following 3 fixed proportional values: 1/3 - 2/3 - 3/3.

ENVELOPE 4 EGs based on CEM-3381 (also 9 X SSM-2024 / board):

- EG1 VCF MM: 4 segments + 1 time - EG2 VCF OB: 4 segments + 1 time - EG3 auxilliary assignable: 4 segments + 1 time - EG4 VCA: 4 segments + 1 time

Some extra special EG modes:
- freerun: finishes the segment even if no more triggered (for percussions)
- reset: a retriggered note goes ON with the previous EG value without restarting
- repeat: repeats the EG if not retriggered when a note finishes
- VCA offset: is a drone mode.

LFO up to 3 delayed modulators (shapes: saw, saw reverse, triangle, random and sample & hold) with variable symmetries:
- LFO1 VCF OB (also matrix assignable)
- LFO2 VCF MM (also matrix assignable)
- LFO3 freely assignable on the matrix like VCA / PWM / VCO.



Only FREE RUN LFO mode and no possible modulation retrig.

 

PERFORMANCE the digital VOICE ALLOCATION ALGORITHM assigns the availabe voices depending on number of installed boards, here's some of the playmodes:
- unison: stacks all available voices
- rotate: each new note is cycled on a voices from 1 to 12 (or less of courses)
- portamento with variable times
- stack:different patches layered in odd or even multiples modes
- split-stack: same as stack with split point
- chorus: a kind of detune to fat up sound
- Microtonalsystem according to 10 preset tables.


The lower row voice status indicates the voice number being playing, pretty nice when using the special rotate mode creating a special analog feeling since all boards cannot sound precisely the same.

 

MATRIX affects a parameter of a function with the output of another like a modular:

SOURCES: DESTINATIONS: note VCO / MM+OB VCF /EG times velocity EG levels EG1-2-3-4 VCO / VCF MM LFO1-2-3 VCF OB / VCO PWM mod weel VCA bender VCO / VCF MM Midi CC# VCF MM / VCO PWM Foot pedal VCO2 random VCO1

 

MIDI knobs do not transmit any recordable CC#, but full sysex implementation.
Sadly no computer editor has been official made nor librarian.

- EG1 VCF MM: 4 segments + 1 time - EG2 VCF OB: 4 segments + 1 time - EG3 auxilliary assignable: 4 segments + 1 time - EG4 VCA: 4 segments + 1 time

 

MEMORY

- 128 RAM patches - 128 ROM patches - 128 RAM performances - 128 ROM performances BATTERY REPLACEMENT model CR lithium 3V 2032 in battery holder replacement is quite easy.

OB-MX PROTOTYPE LEGEND

It seems that some prototype units had a different design and a better sound (info Richard Bugg part of the original team)

 

 

VST PLUGIN / SAMPLED VERSION no official OBMX plugin nor samples set:

OBXD Sonic projects OP-X

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