A polyphonic analog synth produced by Oberheim from about 1978 to 1984. It was Oberheim's first fully integrated polyphonic synth, with all parameters for all voices under one set of patch controls, as opposed to the piecewise approach taken with the Four Voice. The voice architecture was fairly conventional, with two VCOs (one of which could be synced to the other), a traditional Oberheim two-pole lowpass VCF, a VCA with an ADSR envelope generator, and one LFO. It had patch memory with 32 memory locations, and a cassette interface for external patch storage. Curtis integrated circuits were used extensively, another departure from the Four Voice.
The base configuration came from the factory with four voices, but it could be expanded in the field to 6 or 8 voices by adding voice cards. It had two vertical levers, rather close together, for the pitch wheel and mod wheel functions. Near these were a set of switches for shifting the patch up or down one octave, and for controlling the pitch wheel range. The keyboard had a generous five-octave span but was not velocity or aftertouch sensitive. It had no MIDI, being that MIDI had not been invented yet in 1978, although Kenton does offer a retrofit.
Synth player Wayne Famous (McNatt), of the early-1980s New Wave band The Producers, was noted for attaching a guitar strap to an OB-X and wearing it around his neck, in the manner of a keytar. Years of performing while wearing the heavy OB-X caused him back problems later in life.
The OB-SX was a preset synth that used the same electronics as the OB-X. At one point, Oberheim offered a service wherein a performer could send to the factory a data cassette containing OB-X patches, and the factory would build an OB-SX with these patches burned into its ROM.