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Oberheim OB-Xa

Polyphonic Analog Synthesizer

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OB-Xa 1OB-Xa 2OB-Xa 3OB-Xa 4
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Oberheim OB-Xa
Oberheim OB-Xa
4 000.00 street price

In the early 80's all serious synthesizer manufacturers had to try hard to stay on the market after the release of the Prophet-5 synthesizer. The first attempt to grab his bite of the niche was made by Oberheim when he launched OB-X synthesizer, the second – when he nailed it with OB-Xa, released in 1980.

It may seem that OB-Xa is a modernized OB-X, but it is not. As for the circuitry it seems quite close to OB-SX, and it sounds quite the way OB-SX does. The point is that in OB-X an original design was used to build sound circuits based on using discrete elements similar to those used in SEM modules. The synthesizers OB-SX and OB-Xa are based on specialized CEM chips, which were widely used by many synthesizer manufacturers in the early 80's (Crumar, Moog, Roland and Sequential Circuits in Prophet-5).

The synthesizer sticks to the concept of voice cards of the OB series. It was issued with four, six and eight voices. Each voice card comprised:

Two voltage controlled oscillators (VCO) based on CEM3340, producing sawtooth and rectangular waveforms.
Voltage-controlled low-pass filter (LP VCF) which is built on two CEM3320. The ability to switch the number of chips arranged in series allowed you to select the slope of the filter cutoff - 12 and 24 dB per octave respectively.

The voltage-controlled amplifier (VCA) is discrete - the same as in SEM modules.

Two ADSR envelope generators based on the CEM3310 chips, the signal of which is routed to impact VCF and VCA.

Two modulatable low-frequency oscillators (LFO).

Also OB-Xa features one more modulatable LFO, located on the motherboard.

The synthesizer has a self-tuning function with an automatic system of turning off the failed voices. There’s also a useful innovation which is about the possibility of keyboard split and sound layering (there is an opportunity to save eight overlay options and the same number of split zones).

All settings of the synthesizer can be saved in one of 32 patches (in late revisions the number of patches has been increased up to 120).

Oberheim OB-Xa was used by: Depeche Mode, Van Halen, Gary Numan, Jean Michel Jarre, New Order, Paul Sheafer, Prince, Queen, Jethro Tull, Stevie Nicks, Sneaker Pimps, Rush, Bon Jovi.

Country of origin / production: USA

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More info
Usage area
Usage Design/ Form Factor
With Keys 
Hybrid, Digital+Analog 
Analog Voices8
Tone Generator / Sound Synthesis
Oscillator Type VCO (Voltage Controlled Oscillator)
Oscillators per voice16
Waveform/ Spectral form (main generator) Pulse Width Modulation (PWM)
Waveform/ Spectral form (main generator) Saw
Programs/ Voices/ Timbres
Low-pass Filter (LPF) 
Envelope Generator (EG)
Type Synth Action
Number of Keys49
Built-in controllers
Pitch Bend Wheel 
Modulation Wheel 
Audio out
Analogue: 1/4" (6.35mm)2
Voltage 230V
Voltage 120V
Voltage 50-60Hz
Power Supply Built-in, internal
Case/ body
Production start1980
Production end1982
Production ended

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