Oberheim OB-Xa
The Oberheim OB-Xa was the second of Oberheim's OB-series polyphonic analog subtractive synthesizers, replacing the OB-X with updated features. History
The OB-Xa was released in December 1980, replacing the OB-X after only a year on the market. The OB-Xa was the first Oberheim product adorned with blue horizontal pinstripes on black background that would become standard trade dress for future Oberheim products. While the OB-Xa offered the same polyphony as its predecessor (4, 6 and 8-voice models were offered), its keyboard could be split into two halves (each with its own voice) or to layer voices to create thicker sound (essentially making two notes sound for every key pressed). The OB-Xa also added the ability to switch between 2-pole 12dB and 4-pole 24dB filtering. It offered Filter Envelope modulation for oscillator 2 (which allows the pitch to be modulated by the envelope) in place of the OB-X's ability to cross modulate (frequency modulation of the first VCO with the second VCO). Instead of the discrete circuits for oscillators and filters utilized by the OB-X, the OB-Xa (and the Oberheim synths to follow) switched to Curtis integrated circuits. This made the inside of the synth less cluttered, facilitating troubleshooting, and reducing the cost of manufacture. It was getting more difficult to service the OB-Xa due to the scarcity of Curtis chips; however, Curtis in June 2016, Coolaudio and Alfa all started re-manufacturing some of these chips which has breathed new life into the longevity of the OB-Xa and many other synthesizers that use these chips. Impact 
The synth was used in the famous Van Halen song "Jump". Many other 1980s and '90s artists have used the synth including New Order, The Police, Queen, Rush, Rod Stewart, Prince, Miles Davis, Simple Minds and Gary Numan. Hardware re-issues and recreations 
In 2017, Behringer announced it would replicate the CEM3340 VCO chips used in the OB-Xa synthesizer. The widow of chip creator Doug Curtis released a statement clarifying that the replica was made without permission and that Curtis "would be deeply saddened by the attempt of others to trade on his name and to make unsubstantiated claims of equivalency to his original inventions". In 2018, Uli Behringer announced that Behringer would be producing a clone of the OB-Xa known as the UB-Xa, but very little was heard about the instrument until 2022, when they explained that a microprocessor shortage was delaying many of the projects they had announced, including the UB-Xa. The following year, however, Behringer announced that not only was the UB-Xa ready for manufacture, but also that a desktop version would be introduced as well. In May, 2022, the Oberheim OB-X8, a new 8-voice analog synthesizer with the voice architecture and filters of three classic Oberheim models: the OB-X, OB-Xa, and OB-8, along with functionality and features not included on the original models, was announced. The new synthesizer is manufactured by Sequential in partnership with Tom Oberheim. References

Further reading

External links
Vintagesynth
Sequencer.de
I-2000
OB-Xa MP3's @ Babic.com
OB-Xa info, pics and demo by RetroSound

Oberheim synthesizers
Analog synthesizers
Polyphonic synthesizers