Oberheim OB-Xa
| Spec | Detail |
|---|---|
| Manufacturer | Oberheim |
| Year released | 1980 |
| Synthesis type | Subtractive |
| Architecture | Analog |
| Polyphony | 8-voice polyphonic |
| Notable users | Van Halen, Prince, Rush |
| Known for | The brassy 'Jump' chords of 1980s rock |
Overview
The Oberheim OB-Xa is an analog polyphonic synthesizer released in 1980 by Oberheim Electronics. It is an eight-voice, subtractive synthesis instrument with a fully analog signal path. Building on the earlier OB-X, the OB-Xa added a more advanced voice architecture, including a Curtis Electromusic Specialties (CEM) chipset for its oscillators and filters, which contributed to its distinctively rich and powerful tone. The OB-Xa quickly became a staple in professional studios and touring rigs of the early 1980s, prized for its ability to produce thick brass sounds, lush pads, and punchy basses. Its two oscillators per voice, each with sawtooth and pulse waveforms, along with a resonant low-pass filter, allowed for a wide range of timbres. Unlike many later digital synthesizers, the OB-Xa requires careful programming to achieve its best sounds, but its immediate, warm character made it a favorite among keyboardists seeking a strong analog presence. The instrument is also notable for its use in popular music, particularly in the emerging synth-pop and hard rock genres of the 1980s.
History & design
Introduced in 1980, the OB-Xa was Oberheim's follow-up to the OB-X (1979). While the OB-X used discrete circuitry for its voice architecture, the OB-Xa transitioned to integrated circuits from Curtis Electromusic Specialties, specifically the CEM3340 oscillator and CEM3320 filter chips. This change reduced manufacturing complexity and cost while maintaining a high-quality analog sound. The OB-Xa also offered eight voices as standard, whereas the OB-X was available in four, six, or eight-voice configurations. The front panel features a straightforward layout with knobs and switches for real-time control, though it lacks the extensive modulation matrix of some contemporaries. Its keyboard is a standard five-octave, velocity-sensitive design, and it includes a pitch and modulation lever. The OB-Xa was produced until 1984, when it was replaced by the OB-8. Despite its relatively short production run, the OB-Xa left a significant mark on the sound of its era, bridging the gap between the discrete OB-X and the more integrated OB-8.
How it works
The OB-Xa is a subtractive synthesis analog synthesizer. Each of its eight voices contains two voltage-controlled oscillators (VCOs) that generate basic waveforms: sawtooth and pulse (with variable width). These raw waveforms are rich in harmonics. The signal then passes through a voltage-controlled low-pass filter (VCF) with resonance, which removes higher frequencies, shaping the timbre. An envelope generator (ADSR) controls the filter cutoff over time, while a separate envelope controls the amplifier (VCA). The OB-Xa also includes a low-frequency oscillator (LFO) for modulation of pitch, filter, or pulse width. The oscillators can be synced or detuned for thicker sounds. The voice architecture is polyphonic, meaning multiple notes can sound simultaneously, each with its own set of components. The analog nature of these circuits means that each voice can have slight variations, contributing to a lively, organic character. The OB-Xa's signal path is entirely analog, from oscillators to output, with digital control only for the keyboard scanning and patch memory (on later revisions).
Signature sound
The OB-Xa is renowned for its warm, powerful, and brassy timbre. Its two oscillators per voice, combined with a resonant low-pass filter, allow for sounds that range from deep, punchy basses to soaring leads and lush, evolving pads. The filter is particularly praised for its musical resonance and the way it interacts with the oscillators. The OB-Xa's envelope generators are snappy, making it well-suited for percussive attacks. A key characteristic is the ability to stack voices in unison or use the built-in arpeggiator, though the latter is optional. The synthesizer's sound is often described as 'fat' and 'creamy,' with a distinct presence in the mix. It excels at emulating brass instruments, strings, and organs, but also can produce aggressive, cutting leads. The iconic 'Jump' patch by Van Halen is a prime example of the OB-Xa's brassy, anthemic potential, though that specific sound was created on an OB-Xa and later replicated on other Oberheim models. The OB-Xa's sonic signature is a cornerstone of early 1980s pop, rock, and funk.
Notable users & recordings
The Oberheim OB-Xa has been used by numerous influential artists. Van Halen's 1984 hit 'Jump' features a prominent OB-Xa, though the main riff was played on an OB-Xa and later an OB-X. Prince used the OB-Xa extensively in the early 1980s, including on the album '1999' and 'Purple Rain'. Rush employed the OB-Xa on albums such as 'Moving Pictures' and 'Signals', adding its rich textures to their progressive rock sound. Other notable users include Depeche Mode, who used it on their early albums, and Herbie Hancock, who incorporated it into his jazz-fusion work. The OB-Xa also appears in the work of The Police, Queen, and Styx. Its presence on these recordings helped define the synthesizer sound of the 1980s. While exact song credits can vary, the OB-Xa's distinctive tone is recognizable across many genres, from pop to rock to R&B. Its use by these artists has cemented its place in synthesizer history.
Legacy & influence
The OB-Xa's legacy is tied to the golden age of analog polyphonic synthesizers. Although it was succeeded by the OB-8 and later digital instruments, its sound remains highly regarded. The OB-Xa helped popularize the use of polyphonic analog synths in mainstream music, and its brassy tones became a hallmark of the 1980s. In the decades since, the OB-Xa has been emulated in software and hardware, and original units are sought after by collectors and musicians. Its influence can be heard in the work of modern artists who draw on retro synth sounds. The OB-Xa also represents a transitional point in Oberheim's design philosophy, moving from discrete to integrated circuits. Despite not being as widely produced as some competitors, it holds a firm place in the pantheon of classic synthesizers. Its continued use in reissues and emulations ensures that its distinctive voice remains accessible to new generations.
Frequently asked questions
What is the difference between the OB-X and OB-Xa? The OB-Xa uses Curtis integrated circuits for its oscillators and filters, while the OB-X uses discrete components. The OB-Xa also typically has eight voices and a slightly different filter design, resulting in a somewhat more aggressive and defined sound. Can the OB-Xa create sounds beyond brass? Yes, while it is famous for brassy pads and leads, the OB-Xa is versatile. It can produce deep basses, soft strings, percussive plucks, and experimental textures, depending on how the oscillators, filter, and envelopes are programmed. Is the OB-Xa still used today? Yes, many musicians and producers continue to use original OB-Xa units in studios, and its sound is available through software emulations and hardware clones. Its classic tone remains relevant in contemporary music production.