Oberheim FVS-1 Four Voice Vintage Analog Synth in Amazing Condition SN 0397

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"The 4 Voice was introduced in the mid 70s and was one of the first polyphonic synthesizers available. Each of the 4 Synthesizer Expander Modules ( SEMs ) can be assigned to a different note. Splitting voices between modules is also possible, as is monophonic unison mode. In unison mode, it allows EIGHT oscillators per key. A single voice will give you 2 oscillators, 2 envelopes (1 for filter, 1 for volume), an LFO, pulse width modulation and a multimode filter with sweepable mode. The programmer module allows fast saving and recall of programmed sounds.

This particular unit seems to have a factory modification where the programmer section has two 4-stage envelope generators. In a standard 4 Voice, the programmer section has two 3-stage envelope generators as well as a single LFO with rate and depth controls. But in this unit the LFO control pots were set up to control the extra envelope stages (the LFO resistors weren't even installed, hence why this is likely a factory mod). It's actually a very useful mod because the 3-stage envelopes on the SEMs aren't as capable as proper ADSRs. So there is no global LFO, but the unit has the added benefit of having true ADSR envelopes and each individual SEM does still have an LFO of its own."