A polyphonic analog synthesizer
with a 61-note keyboard
. Manufactured in the early 80s
The OB-Xa is an extended version of the OB-X. It is also available with 4-, 6- or 8-voice polyphony.
The synth tops its predecessor by offering 2 LFOs, a 4-pole (24dB/octave) VCF, split/layer keyboard functions, a computer interface plus internal memory storing up to 120 patches and 8 combinations, instead of the 32 sounds on the OB-X. Cross-modulations is no longer featured, but the filter envelope can be used with VCO2.
On the OB-Xa Oberheim switched from using SEM-based circuitry to Curtis hardware. The synth features CEM 3340 (VCO), CEM 3320 (VCF), CEM 3310 (EG) and CEM 3360 (VCA) chips.
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