Korg 700S (1973–1974)

The 700S is sold as the Mini-Korg 700S and internally designated the K-2. It's the two-oscillator version of Korg's first synthesizer, the Mini-Korg 700. The original 700 had a single oscillator, and the 700S adds a second. It's a preset-style monophonic analog synth, not a patchable one, and it predates the Minimoog-era arms race that most people associate with early 70s synths. Sound on Sound (April 1998, p.268) noted in a retrospective on the Mini-Korg family that Vangelis and Kitaro both cut their teeth on a Korg 700. It also noted that the instrument had just a 37-note keyboard, no velocity or pressure sensitivity, and no conventional patch points.

The 700S has a 37-key, three-octave keyboard with a scale selector covering 32', 16', 8', 4', and 2'. The manual describes this as extending the 37-note keyboard into a "full spectrum keyboard." Waveforms are triangle, square, and sawtooth. The control surface is a set of slide controls and tabs rather than a patchbay: Volume, Traveler (the filter/tone-shaping control), Attack, Percussion, and a set of "Instant Set" tabs - Expand, Bright, Sustain, Bender, Repeat, Vibrato, Delay Vibrato, and Portamento/Glide. A separate slide modifier group handles Repeat speed, Vibrato Speed/Depth, and Portamento rate. The effects section includes chorus I and II. Output is via high-impedance (100 kΩ) and low-impedance (5 kΩ) jacks. The unit runs on 117V 50/60Hz at 15W. It measures 29.3 × 11.0 × 4.3 inches and weighs 19.8 lbs. Accessories included a music rack and connection cord. A case, stand, and two-channel expression pedal were optional. The 700S also has two rear adjustable legs for tilting the unit.

The service documentation is unusually complete for a synth of this age. The manual includes full parts lists (resistors, capacitors, transistors including 2SA564S, 2SC828S, 2SC644S, the 2SK-30Y FET, and a TS-200011 IC), printed circuit board references (SB-027), and detailed calibration procedures for pitch, the Traveler filter (low-pass and high-pass Q and cutoff), VCA gate, and ring modulation. The ring modulator adjustment is done with the selector set to Modulator 3, balancing until every pitch is out of tune. The 700S also has a duet/select mode in the effects section. Pitch is adjusted per-octave with trimmer pots (5K, 50K, 10K VRs) at C1, C2, and C4.

The 800DV is essentially two 700S synthesizers in one chassis, per Sound on Sound (April 1998, p.270). So the 700S is the building block for Korg's flagship duophonic of the era. The 700S itself is not rare, but it's not common either, and it sits in the shadow of the more famous MS-series that followed. The manual survives, but period reviews are thin, and original pricing isn't well recorded.

Type: Monophonic analog preset synthesizer (Mini-Korg series)
Keyboard: 37 keys, 3 octaves
Scale: 32', 16', 8', 4', 2'
Waveforms: Triangle, square, sawtooth
Effects: Chorus I/II, ring modulation (Modulator 3), duet
Controls: Volume, Traveler, Attack, Percussion; Instant Set tabs (Expand, Bright, Sustain, Bender, Repeat, Vibrato, Delay Vibrato, Portamento/Glide)
Output: High 100 kΩ / Low 5 kΩ
Power: 117V 50/60Hz, 15W
Dimensions: 29.3 × 11.0 × 4.3 in.
Weight: 19.8 lbs.
Accessories: Music rack, connection cord; optional case, stand, expression pedal