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The Oberheim Xpander which was built in 1984, causing a sweet sensation that continues to blow minds to this very day. The Oberheim Xpander is an analogue, however one must not forget that the analog modules are controlled by digital control signals. An 8-bit processor is used inside.

There is also a keyboard version, the Oberheim Matrix-12 which first appeared in 1985.

VCOs, yes jubilate and rejoice: they are really voltage-controlled oscillators with the waveforms triangle, square and sawtooth. The second VCO still has noise to offer. Of course they can be synchronized, the original source of overtone-rich circular chimes. The VCO2 can control the second in its frequency (FM). The filter can also be modulated by the VCO, which can lead to very interesting sounds, especially at high resonance levels.

The Oberheim Xpander has a multimode filter that offers a lot of different variants: LPF, HPF (1-4 pole), BPF (2 & 4 pole), Notch (bandstop), Phase (3 pole) and combinations: HPF (2- 3 pole)+LPF(1 pole), notch (2 pole) + LPF (1 pole), phase (3 pole) + LPF (1 pole), filter FM can be modulated by Oszillator2 (what special!). 1 pole stands for 6 dB edge steepness, 2 for 12 dB (eg Oberheim SEM), 3 for 18 dB (eg TB-303) and 4 for 24 dB (eg Moog). So everything included! And much more. The special shapes are also extremely interesting in connection with high resonance and the FM.

There are 5 envelopes, which can also be started by LFOs. They are DADSR models, so with a delay before the attack. (For what envelopes and ADSR is, see microQ review). Speaking of the microQ, there's even Freerun, DADR, and Reset modes. The names should speak for themselves. Another special feature is generally the possibility of modulating any possible target from 2 sides. Once again: For me, the Oberheim Xpander system is extremely well designed and intuitive to use, since you simply have to select the appropriate target parameter to see and check your modulations.

Each of the 5 regular LFOs can be triangle, sawtooth (rising and falling), square, random, noise and sampled. Sampled? This is a sample & hold circuit that can come from any modulation source (the list of sources is at the top!) Of course this is not a sampler, but a circuit that takes a sample from the current value of the source with each LFO run and remains so until the next "sample".

Typical of the Oberheim Xpander is its full, warm, very convincing sound! As well as having loads of features, the Xpander sounds good — very good, in fact. Compared to earlier Oberheims, or Moogs and ARPs, the Xpander has a smoother, more sophisticated timbre. Put it next to a Moog or ARP and it sounds mellower, with a more polished '80s feel. Although this was possibly due to different Curtis chips used in the later synths, the Xpander's sound seems to continue a trend by Oberheim towards a less raw and more sophisticated tone than their earlier machines 

Specifications 

Polyphony - 6 voices

Oscillators - 12 VCOs (2 per voice), Linear FM

LFO - 5 LFO's

Filter - 1, 2, 3, 4 pole low pass; 1, 2, 3 pole hi pass, bandpass, notch, phase shift

VCA - 15 per voice, 5 ADSR envelope gens per voice

Keyboard - None

Memory - 100 single / 100 multi

Control - MIDI In/Out/Thru, 6 CV/Gate Inputs, Trigger, 2 pedal inputs

Date Produced - 1984-88

Manual

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