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Oberheim Xpander

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Xpander
Oberheim Xpander
ManufacturerOberheim
Dates1984 - 1988
PriceUS$3995
Technical specifications
Polyphony6[1]
Timbrality6
Oscillator2 per voice
LFO5 per voice
Synthesis typeSubtractive, FM
Filter
  • 1, 2, 3, 4 pole low pass
  • 1, 2, 3 pole hi pass
  • bandpass
  • notch
  • phase shift
Attenuator2 per voice
Storage memory
  • 100 single patches
  • 100 multi patches
Effectsnone
Input/output
Keyboardnone
Left-hand controlnone
External control

The Oberheim Xpander (/ɛksˈpændər/) is an analog synthesizer launched by Oberheim in 1984 and discontinued in 1988. It is essentially a keyboardless, six-voice version of the 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."

Architecture

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Analog Components

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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 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

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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.

Famous users and example uses

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References

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  1. ^ "Oberheim Xpander". Sound On Sound. January 1998. Archived from the original on 6 June 2015.
  2. ^ Widders-Ellis, Andy (December 1989). "Ray Lynch: Exploring the Structure of Music". Keyboard. 15 (12): 29. Lynch takes five in his home studio...Fostex E-16 tape deck...Yamaha TX7, Roland-550, Super Jupiter with programmer, and P-330...Macintosh and Oberheim Xpander above a Yamaha DX7II, AKG ADR-68k reverb above Fostex 4050 SMPTE generator/audio locator, Soundtracs MIDI mixing board.
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