The Oberheim OB-X was introduced in July 1979 as Oberheim Electronics’ new programmable polyphonic synthesiser and represented a major change in the company’s approach to polyphonic instrument design. Earlier Oberheim polyphonic synthesisers such as the Four Voice and Eight Voice had been constructed around multiple Synthesizer Expander Modules, with individual voice modules providing considerable flexibility but requiring a comparatively large and complex instrument. The Oberheim OB-X brought polyphonic synthesis, programming and performance control together behind a single unified control panel.
The Oberheim OB-X was developed during a period in which microprocessor-controlled programmable polyphonic synthesisers were beginning to redefine the professional keyboard market. The Sequential Circuits Prophet-5 had demonstrated the practicality of combining multiple synthesiser voices with patch memory and a common set of controls. The Oberheim OB-X was Oberheim’s response, combining circuitry developed from the company’s existing synthesiser designs with microprocessor control and full programmability.
Rather than abandoning the architecture that had established Oberheim’s earlier instruments, the Oberheim OB-X incorporated established Oberheim circuitry into a more integrated format. The instrument was initially configured with four voices and could be expanded to six or eight voices. Each voice provided two oscillators and two full ADSR envelope generators, allowing the Oberheim OB-X to retain a substantial polyphonic synthesis architecture while making the instrument considerably more straightforward to programme and operate than the earlier multi-module systems.
One of the most important developments was the Oberheim OB-X programmer. The instrument could store 32 complete programs internally, allowing a player to recall previously created sounds without manually resetting the front panel. When a stored program was selected, most front-panel controls became inactive until Manual or Edit mode was selected.
Manual mode allowed the physical positions of the Oberheim OB-X controls to determine the sound directly, effectively operating the instrument in the manner of a conventional non-programmable synthesiser. Edit mode allowed an existing stored program to be recalled and then altered. The controls operated incrementally from their current positions, allowing parameters to be changed without the sound immediately jumping to the physical setting of each knob. Edited sounds could subsequently be written into the instrument’s memory.
The Oberheim OB-X programmer also incorporated a memory-protect facility to prevent accidental erasure of stored programs. Programs could be copied from one memory location to another, while a built-in cassette interface provided a means of storing program information externally using a cassette recorder.
Automatic tuning was another important facility of the Oberheim OB-X. An Auto function tuned all oscillators, while an A-440 reference provided a standard tuning reference. The Master Tune control could shift the entire instrument above or below standard tuning, with its centre detent corresponding to A-440 following the automatic tuning procedure.
The Oberheim OB-X offered several performance functions that extended beyond conventional polyphonic keyboard operation. Polyphonic portamento allowed individual voices to glide between notes, while polyphonic sample-and-hold was incorporated into the modulation system. Dual modulation levers provided pitch-bend and vibrato control.
The Oberheim OB-X Unison function assigned all available voices to a single played note. A further Unison Chord function could be created by combining Unison and Hold. The player could hold a chord, engage Unison, and subsequently transpose the stored chord by playing individual notes across the keyboard.
The Hold system could also sustain individual notes or chords without requiring the keys to remain depressed. When Hold was engaged, played notes remained active until replaced or until the Hold function was disengaged.
The modulation section was programmable and included a low-frequency oscillator with sine, square and sample-and-hold waveforms. Modulation routing and depth controls provided access to multiple modulation possibilities, while the Oberheim OB-X’s oscillator and modulation architecture retained elements associated with Oberheim’s earlier instruments.
The Oberheim OB-X was designed for both studio and live use. Five foot-control inputs were provided for volume, filter, vibrato, sustain and program advance, allowing important performance functions to be controlled without taking the player’s hands from the keyboard.
The instrument also incorporated stereo operation. Individual voices could be positioned through internal pan controls, allowing the separate voices to be distributed across the stereo field. A mono output was available when the Oberheim OB-X was connected to a single amplification or recording channel.
Serviceability was specifically addressed in Oberheim’s original advertising. A field repair kit was offered, while the voice architecture allowed additional voice hardware to be fitted when expanding a four-voice Oberheim OB-X to six or eight voices. The power supply could also be switched between 115 V and 230 V operation.
The Oberheim OB-X was the first instrument in what became Oberheim’s classic OB series and established the basic direction that would subsequently produce the Oberheim OB-Xa and Oberheim OB-8.
Its importance lies partly in the transition it represented. Oberheim’s earlier polyphonic instruments demonstrated the potential of combining multiple synthesiser voices, but the Oberheim OB-X brought that concept into the emerging era of practical programmable polyphonic synthesis. A single set of controls, microprocessor management and 32-program storage made a complex polyphonic synthesiser considerably easier to use in recording sessions and live performance.
The Oberheim OB-X also established Oberheim as a direct participant in the rapidly developing market for self-contained programmable polyphonic synthesisers at the end of the 1970s. The competition that developed between Oberheim and Sequential Circuits helped define the development of American analogue polyphonic synthesisers during the following years.
The architecture introduced with the Oberheim OB-X remained influential within Oberheim itself. The Oberheim OB-Xa followed in 1981 and the Oberheim OB-8 in 1983, developing the OB-series concept while retaining the central idea established by the Oberheim OB-X: a large polyphonic analogue synthesiser with comprehensive front-panel control, programmable memory and a performance-oriented keyboard interface.
More than four decades later, the historical importance of the Oberheim OB-X, Oberheim OB-Xa and Oberheim OB-8 was formally recognised when their architectures became the foundation for the modern Oberheim OB-X8. The Oberheim OB-X therefore stands not simply as an individual late-1970s synthesiser, but as the starting point of one of Oberheim’s most significant instrument families.
Features
- Four-voice polyphonic architecture expandable to six or eight voices
- Two oscillators per voice
- Two full ADSR envelope generators per voice
- 32-program internal memory
- Automatic oscillator tuning with A-440 pitch reference
- Manual and Edit programming modes
- Polyphonic portamento and polyphonic sample-and-hold
- Unison and transposable Unison Chord functions
- Built-in cassette interface for program storage
- Five-octave keyboard with dual modulation levers