The OB-X was Oberheim's first fully programmable polyphonic synth. It's predecessors, the Four-Voice and Eight-Voice, were polyphonic but monotimbral programming was less than intuitive. Each voice card in the OB-X is in essence an expanded SEM controlled by a common user interface. The OB-X found it's way onto many late '70s and early '80s albums, including Rush's "Tom Sawyer" and Van Halen's "Jump". It remains a favorite of mine in the studio, especially with the addition of Encore Electronic's MIDI retrofit." The OB-X's metal case is built like a tank and features laminated wood ends and a hinged lid for easy maintenance and tuning. The pitchbend and modulation levers reside directly to the left of the 61 note Pratt and Reed keyboard assembly. Octave select, pitchbend range, and Osc 2 mod destination switches round out the section. The OBx features 32 patches, each storing data for the two multi-waveform oscillators, VCA, VCF, associated envelopes, and LFO. The oscillators feature saw and square waveforms, and two selectable volume levels for mixing. The pulse width of the square wave can only be controlled by the LFO, not manually. The resonant 12db/octave filter features full, half, and zero keyboard tracking in addition to adjustable envelope and LFO modulation amounts. ROM Hack Oberheim OBX Owner's and Service Manauls Encore Electronics OB-X MIDI Retrofit