Oberheim XP-1 Xpander & Xk-1 MIDI Keyboard Controller SN G50437 & Z631187

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"The Oberheim Xpander (model designation XP-1) is a legendary six-voice desktop analog synthesizer released in 1984. It is widely celebrated by sound designers as one of the most flexible non-modular analog synthesizers ever constructed. By pairing rich analog audio components with an innovative digital control logic, the Xpander achieved the deep routing capabilities of a modular system without requiring any physical patch cables.

The Oberheim XK (also known as the OB-Xk) is a programmable MIDI keyboard master controller released in 1985. It does not generate any internal sounds on its own; instead, it was engineered primarily as a dedicated, rugged companion hardware controller for Oberheim’s legendary Xpander and Matrix-12 synthesizer modules.



SPECS:

Serial #'s:

Xpander: G50437

XK-1 Controller: Z631187

Voice Design: Six independent voices utilizing custom Curtis CEM chips (two oscillators per voice for a total of 12 VCOs).

Matrix Modulation: A matrix system that routes 27 modulation sources—including 5 LFOs and 5 envelope generators per voice—to 47 destinations.

15-Mode Multi-mode Filter: Goes far beyond standard low-pass filters to offer various unique configurations of low-pass, high-pass, band-pass, notch, and phase shifters.

Multitimbral Versatility: Features 6-part multitimbrality, allowing it to function as a 6-voice polyphonic synth, six completely separate monophonic synthesizers, or a complex multi-patch stack.

Hardware Connectivity: Includes extensive MIDI implementation alongside 6 dedicated Control Voltage (CV) and Gate inputs, which can act as a CV-to-MIDI converter.

Keybed: 61 unweighted, synth-action keys featuring both attack/release velocity and channel aftertouch.

Physical Build: Built with a heavy, durable black steel metal chassis flanked by Oberheim’s classic genuine solid wood end cheeks.

Performance Controls: Equipped with Oberheim's signature dual paddle-style Pitch and Modulation levers, alongside one assignable continuous control slider.

Power Requirements: Operates via a standard 9V DC POSTIVE-CENTER power supply *NOT INCLUDED*

3-Zone Layout: The keyboard can be split, overlapped, or layered into three distinct zones across any user-defined note ranges.

MIDI Routing: Each of the three zones can be assigned to its own independent MIDI transmit channel (1–16) and program patch number.

Direct Patch Access: The front panel allows immediate selection of the first 100 single patches and 100 multi patches on external synth hardware.

Arpeggiator: Includes a fully featured, programmable performance arpeggiator that can be synced to either an internal clock or an external hardware clock via a 1/4" trigger input.

Performance Modes: Built-in Chord Memory and Hold functions for latching notes and transposing chord shapes across the keybed.

Transport Controls: Sends MIDI sequencer Song Select, Start, and Stop commands directly from the top interface.

ACCESSORIES INCLUDED: Includes power cable, adapter and 15" MIDI Cable

UNPACKAGED WEIGHT: 42 lbs.

Xpander: 27 lbs.
Xk-1 Keyboard: 15 lbs.

UNPACKAGED DIMENSIONS: 72" x 10" x 22"

Xpander: 33" x 6" x 12"
Xk-1 Keyboard: 39" x 4" x 10"