The Oberheim OB-Xa was Oberheim's overhaul of their first compact synthesizer, the OB-X. The OB-Xa was released in 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 reduced the cost of manufacture. However, today it's much easier to fix an OB-X than OB-Xa, as Curtis parts are getting scarcer, whereas discrete parts used in OB-X are almost always readily available.

Aside from hardware changes, the OB-Xa had better interface features compared to OB-X. These included being able to split the keyboard into two halves with different voices; 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 OB-X voice architecture, was cross modulation, or frequency modulation of vco with the second vco. When done with analogue circuits, it's a unique sound made famous by Prophet 5 and its poly-mod section. Lack of this somewhat reduced the range of sounds possible on OB-Xa.