Oberheim Modular System? Update: OB-Xa Modular

via this auction

Details Google translated:

"To the instrument: This instrument is an absolute rare piece and a sole specimen/single copy. Here one can buy a Synthesizer, which otherwise nobody has. The complete prehistory of the instrument is not to be clarified any longer completely, it acts however obviously around the prototypes of a similar modular system of upper home from the year 1982. Construction units from the famous OB-X and Whether-Xa Synthesizern of Tom upper home are used. The sound reminded very much of the looked for OB-1 Synthesizer, is however substantially fatter and more pressureful and because of the modular structure many more flexibly due to the 3 VCO´s.
Everything is to be out-gotten by ultrafetten basses, alive Leadsounds, elektonischer Percussion, (poly) rhythmic sequences, noises and the most driven off sounds of effect from this “crate” with something trouble and consideration. The basic sound is fat, warmly, alive, sometimes somewhat dirtily, thus 100% genuine similar to! The filter sounds upper home typical see industrial union warm.

3 VCO with the waveform-shaping saw tooth, triangle and rectangle (+ PWM, FM, Sync).

1 MIXER with 5 entrances and 1 exit

1 VCF Lowpass with 24 DB/Oktave and 3 modulation entrances (Env., cut off, Resonance). Self oscillation is possible.

2 LFO with the waveform-shaping saw tooth, triangle and rectangle. The range of control of the LFO´s is quite far, for completely fast modulations takes one the VCO anyway.

2 ADSR with good reason fast Attack. Not completely as fast as Minimoog and ARP-2600, but faster than all digital Synthesizer envelopes. For electronic Perkussion of all play ways it is fast enough.

To those it to say, thus execution of kind of condition gives 2 VCA to few.

Here power pack and power switches are accommodated power module and as characteristic per quadruple a fragment for in or outgoing CV and gate signals, which offers very various Verbindungsmöglichkeiten with external analog equipment from in former times or today.

MIDI INTERFACE, a previous owner inserted to kind of condition the Midiinterface of Döpfer. Beside the normal spielbarkeit over a Midikeyboard still two additional control voltages are spent, which can steer arbitrary modules of the instrument. With the correct attitude and wiring one has even notice dynamics, etc.

1 NOISE, for wind, Snares and other noise-clung sounds is to be used this Noise module.

1 RING MODULATOR to use for disharmonische and metallic sounds. This ring modulator belonged however to the brachialen sort and provides for very distorted and bad sounds. A noble ring modulation A la Vermona RM-1 is not to be expected here; here gehts correctly to the thing.

2*4 MULTIPLE, this module serves for mixing and distributes from control voltages and also as adapters between the banana plugs of the instrument and the generally common jack plugs (6,3mm).

In addition an extensive assortment of the banana plugs belonging to this system is contained."

Update via Feinstrom in the comments:
"I am the former owner, sold it to him some years ago.
It is an OB-Xa voiceboard with jacks and some DIY. Not Oberheim-made, no prototype, built in the 90s or so. And the guy knows all that.
The sound is nice, though."