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Oberheim OB-Xa Polyphonic Synthesizer

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The Oberheim OB-Xa was Oberheim's overhaul of their first compact synthesizer, the OB-X.

The OB-Xa was released in December 1980, a year after the OB-X was released. Instead of discrete circuits for oscillators and filters, the OB-Xa (and the Oberheim synths to follow) switched to Curtis integrated circuits. This made the inside of the synth less cluttered, reducing the labor required to replace bad parts, and reducing the cost of manufacture. However, today it's much easier to fix an OB-X than an OB-Xa, as Curtis parts are getting scarcer, whereas discrete parts used in the OB-X are almost always readily available.

Aside from hardware changes, the OB-Xa had better interface features than the OB-X. These included being able to split the keyboard into two halves with different voices and the ability to layer voices to create thicker sound (essentially making two notes sound for every key pressed). Polyphony stayed the same - again 4, 6 and 8-voice models were offered.

One function that did disappear from the OB-X voice architecture was cross modulation, or frequency modulation of the first VCO with the second VCO. When done with analogue circuits, it's a unique sound made famous by the Sequential Circuits Prophet 5 and its poly-mod section. The lack of this feature somewhat reduced the range of sounds possible on the OB-Xa.

Technical Specifications
Type: Analog
Synthesis: Subtractive
Oscillators: 2
Waveforms: Saw Down, Square, White Noise
Envelopes: 2
Evelope Paramerters: Attack, Decay, Sustain, Release
Filters: 1
Types: 12dB Slope (2-pole), 24dB Slope (4-pole), Low Pass, Resonance
Filter Modulation: Keyboard, Knob, LFO, Mod Wheel
LFO: 2
LFO Parameters: Sample & Hold, Sine, Square
Polyphony & Tuning
Polyphony: 8
Timbrality: 2
Tuning: Standard
Patches RAM: 120
Storage: Internal
Editing: CV
Case: Keyboard
Keyboard: 61 keys, Non-weighted, Plastic
Controls: Knobs, Mod - Wheel, Pitch - Lever, Pedal - Volume
Display Type: LED
Audio Output Connections: 1/4" Phone Jack, Mono Out
Audio Output Count: 1
Year Released: 1980
Year Discontinued: 1982
Used By
Van Halen, Laurie Anderson, Miles Davis, Bon Jovi, Electric Light Orchestra, Jean Michel Jarre, Chaka Khan, Stevie Nicks, Gary Numan - Warriors (1983), Mike Oldfield - Crises (1983), Mike Oldfield, Prince, Queen, Rush, Scandal, , Silent Running, Simple Minds, Styx, Talk Talk, The Police, The System, The Stranglers, The Thompson Twins, Paul Young
Manuals & Documents
MSRP List Price: $5595 - convert
Retail Street Price: $5000 - convert

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