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Oberheim | OB-X


The Oberheim OB-X is an analog polyphonic sound synthesizer.

First commercially available in June 1979, it was introduced to compete with the Sequential Circuits Prophet-5, which had been successfully introduced the year before. About 800 units were produced with moderate success before the OB-X was discontinued in 1981, replaced by the updated and streamlined OB-Xa. The OB line developed and evolved after that with the OB-8 before being replaced by the Matrix series.

The OB-X was the first Oberheim synthesizer based on a single printed circuit board called a "voice card" (still using mostly discrete components) rather than the earlier SEM (Synthesizer Expander Module) used in Oberheim semi-modular systems, which had required multiple modules to achieve polyphony. The synthesizer's built-in Z-80 microprocessor also automated the tuning process. This made the OB-X less laborious to program, more functional for live performance, and more portable than its ancestors.

The "X" in OB-X originally stood for the number of voice-cards (notes of polyphony) installed. It came in four, six, and eight-voice models with polyphonic portamento, and sample and hold. Even the 4-voice model was expensive at US$4,595. The entire range used "paddle" levers for pitch and modulation, Oberheim's answer to the "wheel" controls of the Prophet-5. Though these controls were never as popular as the standard pitch and modulation wheels, the philosophy was to mimic the motion of a guitar player bending the strings on their guitar. On most other synthesizers the pitch bend wheel was on the left, and the modulation wheel to the right of it; on the OB-X Oberheim placed them in the opposite relative positions. In addition to this unique configuration the polarity of the paddles was distinctive; the player would pull back on the pitch lever to bend the pitch sharp, and push forward to bend flat.

It featured a 2 pole VCF lowpass filter with its own ADSR, a VCA with ADSR, a flexible LFO section, polyphonic sample and hold, polyphonic portamento and 32 patches of memory. Capable of lush analog synth sounds comparable to the Sequential Prophet 5. The OB-X also gives you Polymod functionality, something that the OB-Xa and OB-8 do not have.

Engine TypeAnalog
Voices (max)8
Engine Detailed2 VCO's per voice (sawtooth or pulse)
Filter (VCF)2 Pole lowpass with ADSR envelope
Envelope (VCA)1 ADSR VCA envelope
Memory32 patches
Key typeKeys
CV-gateCV / Gate on voice 1 only
Produced:1979 - 1979
Legend: Obvious Y: Yes, N: No, N/A: Not Applicable
VCO Voltage Controlled Oscillator DCO Digital Controlled Oscillator
LFO Low Frequency Oscillator Sub Sub Oscillator
VCF Voltage Controlled Filter VCA Voltage Controlled Amplifier
Velocity As with a piano, the harder you hit a key, the louder the sound, unlike most organs which always produce the same loudness no matter how hard you hit a key. Aftertouch Pressing a key after you activated it. Channel Aftertouch, no matter which key, it will send a Channel message. Poly Aftertouch, sends the pressure per key instead of the whole channel.
Values for OSC, LFO, Filter, Envelope are per voice unless stated otherwise.


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