OB-Xa

Introduced in 1980, this synth marked Oberheim's bold shift to Curtis CEM chips, streamlining production while delivering the aggressive, iconic tones that defined early '80s music—from Van Halen's "Jump" to Prince's lush layers.

At its core, it packs 2 VCOs per voice (sawtooth, pulse with PWM, and noise) across 4, 6, or 8-voice polyphony, routed through a standout switchable filter: 12dB/oct (2-pole) for that classic Oberheim bite or 24dB/oct (4-pole) for deeper resonance. Dual ADSR envelopes shape the VCF and VCA, with a single LFO offering sine, square, and sample & hold for modulation, plus extras like portamento, unison, chord memory, and keyboard split/layering for bi-timbral tricks. The 61-key synth-action board sits atop a hefty wooden chassis—40 inches wide, 20 deep, 6 high, and 45 pounds—loaded with front-panel sliders, switches, and 32 to 120 patch memories (4 banks standard, expandable). Left-hand pitch/mod wheels add expressive control, all powered by a stable analog subtractive engine.

Players cherish its massive, "bigger than life" sound—sizzling pads, buzzy strings, and thunderous basses in unison mode—often calling it the peak of early Curtis-based polysynths for its attitude-packed personality. Sure, parts can be tricky to source these days, and it lacks MIDI natively, but its raw power and self-resonant filters keep it a studio legend.