The Oberheim Xpander 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:

Architecture

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 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: 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.

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