Oberheim OB-X

Released in 1979, the Oberheim OB-X was the first of Oberheim's OB-series polyphonic analog subtractive synthesisers. The OB-X was introduced to compete with the Sequential Circuits Prophet-5, which had been successfully introduced the year before

Released in 1979, the Oberheim OB-X was the first of Oberheim's OB-series polyphonic analog subtractive synthesisers. The OB-X was introduced to compete with the Sequential Circuits Prophet-5, which had been successfully introduced the year before.

Essentially the OB-X was six of Oberheim's previous SEM (Synthesiser Expander Module) mono-synth circuit boards, one for each voice, bolted to grouped controls on the front, with the six boards summed through the filter and amp envelope sections etc. The OB-X was suffixed with the 'X' to designate that the voices or polyphony could be varied depending on how many voice boards/cards were inserted & could be configured with 4, 6 or 8 voices/cards. The OB-X also featured a built in Zilog Z80 CPU which was common in many devices at the time including the Emulator & Prophet-5, and the computer handled tuning and patch memory tasks.

The OB-X was superseded a year later in 1980 by the OB-Xa which was essentially the same synth, but it now sported the classic Oberheim blue horizontal stripes design also featured on the DMX drum machine of the same year. The main difference with the OB-Xa was the use of Curtis chips rather than the discrete circuits of the original OB-X and the addition of a switchable 2-Pole 12dB/Octave or 4-Pole 24dB/Octave filter with added modulation abilities.

The OB-Xa used a Curtis 3340 VCO, the 3310 voltage controlled envelope generator, the 3320 Voltage Controlled Filter & the 3330 Voltage Controlled Amplifier chips making in much more reliable & reducing circuit board production costs. The OB-Xa also added a split keyboard feature & the ability to layer or 'Double' sounds like the Jupiter-8 could do. The OB-Xa was most famously used on the track Jump by Van Halen.

Finally in 1983 the OB-Xa was replaced by the OB-8 which was fixed at 8 voices and added further upgrades.

Faced with stiff competition from the deluge of 1980's Japanese digital synth innovations combined with the introduction of MIDI, Oberheim went bust in 1985, was restructured and soldiered on making the initial Matrix series products before finally going broke again & being bought by Gibson in 1988, with the Matrix-1000 rack module being the last product made & released in the same year.