Oberheim OB-Xa

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Manufacturer Oberheim
Dates 1980 - 1982
Price US$4595 - US$5595
Technical specifications
Polyphony 4, 6 or 8 voices
Timbrality Bitimbral
Oscillator 2 VCOs per voice
Synthesis type Analog Subtractive
Filter Switchable 12dB/oct and 24dB/oct resonant low-pass
Attenuator 2 x ADSR; one for VCF, one for VCA
Aftertouch No
Velocity sensitive No
Memory 32 - 120 patches
Effects None
Keyboard 61-key
Left-hand control Pitch
External control Oberheim system

The Oberheim OB-Xa was Oberheim's overhaul of their first compact synthesizer, the OB-X.[1][2]

The OB-Xa was released in December 1980, a year after the OB-X was released. Instead of discrete circuits for oscillators and filters, the OB-Xa (and the Oberheim synths to follow) switched to Curtis integrated circuits. This made the inside of the synth less cluttered, reducing the labor required to replace bad parts, and reducing the cost of manufacture. However, today it's much easier to fix an OB-X than an OB-Xa, as Curtis parts are getting scarcer, whereas discrete parts used in the OB-X are almost always readily available.

Aside from hardware changes, the OB-Xa had better interface features than the OB-X. These included being able to split the keyboard into two halves with different voices and the ability to layer voices to create thicker sound (essentially making two notes sound for every key pressed). Polyphony stayed the same - again 4, 6 and 8-voice models were offered.

One function that did disappear from the OB-X voice architecture was cross modulation, or frequency modulation of the first VCO with the second VCO. When done with analogue circuits, it's a unique sound made famous by the Sequential Circuits Prophet 5 and its poly-mod section. The lack of this feature somewhat reduced the range of sounds possible on the OB-Xa.

Albums that feature the OB-Xa[edit]


External links[edit]