MATRIXSYNTH: Original Oberheim SEM Synthesizer Expander Module w/ Extra CV I/O

Monday, February 10, 2020

Original Oberheim SEM Synthesizer Expander Module w/ Extra CV I/O


via this auction

Some pics of the inside below.

"This is an amazing original all-analog Tom Oberheim SEM (Synthesizer Expander Module) in excellent condition and sounding unbelievably creamy, alive and totally fabulous. It has been modified/expanded with extra patch points, switches and pots. SEMs were produced between 1974 and 1979. The serial number sticker fell off decades ago, so I'm not sure the exact production year. It has the 1180 circuit board, as seen in the photos. Everything has been tested and functions perfectly except the pot on the 3rd (right-most) Attenuator, but none of the Attenuators are connected to any SEM circuitry.

The SEM is monophonic, with two VCO's (each with sawtooth or variable-pulse waveforms). The LFO is triangle wave only. The VCF is 2-pole multimode (low-, band-, hi-pass, band-reject) with an ASR (Attack, Decay and Sustain) Envelope Generator or External CV control. The VCA has an ADR (Attack, Decay and Sustain) Envelope Generator or External CV control.

Top Patch Point Jacks
CV-IN, GATE-IN / MOOG GATE / ENV2 GATE IN / LFO OUT / EXT2 IN / AUDIO-IN / AUDIO-OUT

Additional Added Top Panel Controls/Patch Points
OSC CV SYNC switches CV.1 and CV.2 / Overall VOLUME Knob / FILTER CV.1 / ENV SYNC OFF

Front Panel Added Patch Points
Lfo Trigger / Env1 out / Env2 out
Ext mod in (VCO1) / Cv2 in (VCO1) / Pulse out (VCO1) / Saw out (VCO1)
Ext mod in (VCO2) / Cv1 in (VCO2) / Cv2 in (VCO2) / Pulse out (VCO2)
Ext mod in (FILTER) / Cv2 in (FILTER) / Ext1 in (FILTER)
VCA Cv in
ATTENUATORS (x3) - Each with In/Out/Pot - Note potentiometer on right-most Attenuator does not work - not part of SEM circuitry."

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