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Oberheim SEM

Synthesizer Expander Module

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Oberheim SEM
900.00 street price

In the 70s Tom Oberheim became famous as a talented inventor of guitar effects. Its ring modulator and phase shifter, produced under the Maestro brand, were real bestsellers. At the same time, Tom was the official dealer of ARP synthesizers in Los Angeles. And at some point, with the support of Dave Rossum (the founder of E-mu Systems), he decided to try himself in the synthesis engineering. The result of this successful attempt was SEM, which was demonstrated at the Los Angeles Convention of Audio Engineers in May 1974.

The module was positioned as an auxiliary monophonic synthesizer for operating with a sequencer or with a monophonic synthesizer for layering and sound enrichment.

It is built on the basis of two voltage controlled oscillators that produce a sawtooth and square waveform (duty cycle can be adjusted).

For each, the tuning, FM and PW modulation is provided. The modulation source can be an envelope generator, LFO or an external signal.

The LFO has a frequency controller and produces only a triangular wave.

Two envelope generators have time adjusters for attack, decay and sustain.

Unlike modern synthesizers with four-stage VCF, SEM has a two-step voltage controlled filter with a slope of 12 dB per octave. There were many fans of this particular filter. Although it does not sound as bright as the four-stage filters, it has four modes of operation: lower, upper, band and notch.

Country of origin / production: USA

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More info
Usage area
Sound Module/ Tone Generator 
Analogue (A) 
Tone Generator / Sound Synthesis
Oscillator Type VCO (Voltage Controlled Oscillator)
Oscillators per voice2
Waveform/ Spectral form (main generator) Pulse Width Modulation (PWM)
Waveform/ Spectral form (main generator) Saw
High-pass Filter (HPF) 
Low-pass Filter (LPF) 
Band-pass Filter (BPF) 
Band-reject Filter (BRF/ BEF) 
Envelope Generator (EG)
Audio out
Analogue: 1/4" (6.35mm)1
Audio in
Analog 1/4"1
Voltage 110V
Voltage 60Hz
Power Supply Built-in, internal
Case/ body
Production start1974
Production end1979
Production ended

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Oberheim 2 Voice
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  Analog Duophonic Synthesizer   3 000.00 U.S.Dollars

Keeping track of the success of his first synthesizer and willing to create a new product, Tom Oberheim simply combined two SEM modules with a keyboard and a basic sequencer putting them into one housing. This made it possible to get a duophonic...

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  Synthesizer Expander Module   500.00 U.S.Dollars

The expansion module, designed to function together with the "older brothers". It doesn’t have its own keyboard, VCF, VCA, on board - only one VCO and LFO. According to the manufacturer's idea, this module should be integrated with, for example, ARP Axxe...