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Oberheim Xpander

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    The Oberheim Xpander is a rack version of Oberheim Matrix-12 and was an analog synthesizer launched by Oberheim in 1984 and discontinued in 1988. It is essentially a keyboardless, six-voice version of the Oberheim OB-8 and Matrix-12 (released a year later, in 1985). Utilizing Oberheim's Matrix Modulation technology, the Xpander combined analog audio generation (VCOs, VCF and VCAs) with the flexibility of digital controls logic.

    The Xpander "Owner's Manual, First Edition" describes the technology as this:

    "An analogy to the Matrix Modulation system might be all of those millions of wires that existed on the first modular synthesizers. As cumbersome as all of that wiring was, it allowed the user to connect any input to any output, resulting in sophistication and flexibility unmatched by any programmable synthesizer...until now."

    Analog Components

    Each of the six voices of the Xpander is completely independent. That is to say, each could be configured to create a different timbre - this is accomplished via the multi-patch mode which will be described below.

    Starting at waveform generation, each voice has two voltage controlled oscillators (VCOs). Each of which is capable of generating sawtooth, triangle, pulse or noise waveforms. Furthermore, the "duty cycle" of the pulse width can be modulated as well. Although perhaps better known for subtractive synthesis, the Xpander is also capable of frequency modulation (FM) synthesis by modulating VCO #1 with VCO #2.

    Moving on from the VCOs, the signal then passes through a multi-mode voltage controlled filter (VCF). The available modes on the filter are:

    one-, two-, three- and four-pole low pass
    one-, two and three-pole high pass
    two- and four-pole band pass
    two-pole notch
    three-pole phase shift
    two- and three-pole high pass plus one-pole low pass
    two-pole notch plus one-pole low pass
    three-pole phase shift plus one-pole low pass
    From the filter, there are two sequential voltage controlled amplifiers (VCAs) through which the signal must pass. And finally the audio is delivered to a variety of outputs: mono, stereo and six independent outputs (corresponding to the six voices).

    Digital Controls

    Of those analog audio components (VCOs, VCF and VCAs), each can be modulated by several different digital controls.

    ADSR Envelopes - each voice can have up to five envelope generators. Each envelope is of the standard Attack-Decay-Sustain-Release model (ADSR), with the addition of an initial Delay phase, thus making them DADSR envelopes, to be exact.

    Low Frequency Oscillators (LFOs) - each voice can have up to five LFOs applied. Each LFO can have a different waveform: triangle, square, up-saw, down-saw, random or noise. Additionally, a sampling mode is provided, whereby an independent source (e.g. a different LFO) is sampled at a set frequency.

    Lag Generator - the lag function is similar to portamento on traditional synthesizers. However, the lag modulation in the Xpander can be applied to any control or audio signal.

    Ramp Generators - each voice can have up to four ramp generators. Similar to the attack portion of an ADSR envelope, the ramp generates a linear signal from zero to the user-defined ramp height.

    Tracking Generators - there are three tracking generators available for each voice. The tracking generator provides a mapping from a control source (e.g. key range on the keyboard, or volume pedal, or mod wheel) to a modified output, based on the user-defined settings of the generator.
    Type: Analog, Digital
    Synthesis: Frequency Modulation, Subtractive
    Oscillators: 2
    Waveforms: Square, Triangle
    Envelopes: 4
    Evelope Paramerters: Delay, Attack, Decay, Sustain, Release
    Filters: 2
    Types: 6dB Slope, 12dB Slope (2-pole), 18dB Slope, 24dB Slope (4-pole), Band Pass, High Pass, Low Pass, Notch, Phase Warp , Resonance
    Filter Modulation: Envelope, Input, Keyboard, Knob, LFO, Oscillator
    LFO: 5
    LFO Parameters: Noise, Sample & Hold, Saw Up, Saw Down, Square, Triangle, Clocked, Delay
    Polyphony & Tuning
    Polyphony: 6
    Timbrality: 6
    Tuning: Standard
    Patches RAM: 100
    Multipatches RAM: 100
    Storage: Internal, 6
    Editing: CV, MIDI
    Case: Desktop, Module
    Controls: Buttons, Knobs
    Display Type: LCD, Backlit
    Dimensions (WxDxH): 33 x 12.5 x 6 inches
    Audio Output Connections: 1/4" Phone Jack, Mono Out
    Audio Output Count: 8
    MIDI Ports: IN, OUT, THRU
    CV Ports: CV IN, CV OUT, Gate In, Gate Out
    Year Released: 1984
    Year Discontinued: 1888
    Units Made: 2000
    Used By
    Steve Roach, Vince Clarke, Nine Inch Nails, Yello, Chemical Brothers, Meat Beat Manifesto, Larry Fast, Baby Ford, Chris Franke, Frontline Assembly, Front 242, Jan Hammer, Miles Davis, Human League, Mark Isham, Nitzer Ebb, Orbital, Steve Porcaro, Propaganda, Stefan Reinert, Mark Shreeve, K-H Stockhausen, Switzerland, Joe Zawinul
    Manuals & Documents
    MSRP List Price: $3995 - convert
    Retail Street Price: $3700 - convert
    Used Price: $2500 - $3500+ - convert
    YouTube Videos
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