Korg PS-3100 (1977–1981)
The PS-3100 is one of the earliest commercially available polyphonic synthesizers. Korg released it in 1977, before the company had made its mark on the synth big league. It has 12-voice polyphony across a 73-note unweighted keyboard, with a dedicated analog VCO per voice generating sawtooth, triangle, and pulse waveforms. Internally it uses a divide-down architecture. Each key generates a square wave from a top-octave generator IC, which then passes through string-style filter circuitry and dedicated voice cards. Each card has its own 12 dB/octave low-pass filter and ADSR envelope.
The instrument sits in a large, solid wooden cabinet and is quite heavy for a synth of its era. It has no patch memory - all settings are manual, and there are plenty of knobs to twiddle. The keyboard can be split into two independent halves, but the split point is fixed and cannot be changed. One owner described the keyboard as terrible for conventional playing but excellent for drones. Besides the main stereo outputs, there are individual outputs per voice, a headphone jack, and CV/Gate connectivity. There is no MIDI. Sound On Sound (February 2001, p.254) noted that the PS-series was conceptually similar to the MS monosynths that followed, and that a Kenton retrofit exists to add basic MIDI note on/off control.
The PS-3100 is good at strings, pads, and ethereal textures, and it saw use on many film and television scores of the era. It was reportedly used by Keith Emerson. The related PS-3200 is essentially a PS-3100 with two additional keyboards and more memory. Sources conflict on whether the PS-3100 was first in the PS series or second after the PS-3200. Production ran until roughly 1980-1981, after which Korg moved toward more mainstream instruments like the Poly-61 and DW series.
The PS-3100 is rare and sought after today, typically listing between $3,500 and $6,000 depending on condition. Common issues include dirty or worn key contacts, power supply capacitors needing replacement, and voice cards drifting out of tune. Korg offers no spare parts, so repairs require a skilled technician.
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