SX-240 8-Voice Programmable Polyphonic Synthesizer © 1984 Kawai
The SX-240 is a premium, highly sophisticated 8-voice analog polyphonic synthesizer. Emerging at a time when the synthesizer market was rapidly pivoting toward the digital domain following the release of the Yamaha DX7, the SX-240 represents one of the final, most advanced achievements in classic Japanese microprocessor-controlled analog synthesis. It was marketed to compete directly with mid-range heavyweights like the Roland Juno-106 and Korg Poly-61, but it offered a far deeper dual-oscillator architecture.
The internal sound engine of the SX-240 consists of 8 true analog voices driven by highly stable Digitally Controlled Oscillators (DCOs). Unlike many entry-level polysynths of the era that limited users to a single oscillator per voice, the SX-240 features 2 DCOs per voice (providing 16 oscillators in total). These feed into a warm, resonant 24 dB-per-octave low-pass analog filter section built around proprietary SSM (Solid State Micro Technology) chips. The voice architecture supports extensive performance versatility, featuring selectable Poly-8, Dual (layering two patches into a 4-voice stack), and Split keyboard modes.
The physical hardware balances a sleek, modern aesthetic with traditional construction, featuring a dark metal front panel accented by vibrant teal and yellow programming lines, bounded by dark faux-wood end cheeks. For patch management and navigation, Kawai abandoned large arrays of dedicated sliders in favor of a centralized alpha-dial workflow paired with an integrated 8-character green fluorescent alphanumeric display. The rear panel features factory-installed 5-pin MIDI In/Out/Thru ports, standard stereo outputs, and a cassette interface for external data storage.
The Teisco Corporate Heritage: The SX-240 wasn't built from scratch by Kawai's traditional acoustic instrument division. It was actually the final masterpiece designed by the legendary Teisco engineering team. Kawai acquired Teisco in the late 1970s and gradually phased out the brand name. Early prototype units and initial production runs in specific regions still carry the "Teisco" logo on the casing before the line was globally rebranded under the Kawai banner.
The SSM Filter Warmth: Under the hood, the lush, aggressive, and highly musical character of the SX-240's filter section is driven by the SSM2044 filter chip. This is the exact same legendary integrated circuit responsible for the signature analog warmth found inside the Korg Polysix, Korg Mono/Poly, and early Emulator samplers, giving the SX-240 a distinctively fat, vintage tone that easily cuts through modern digital recordings.
The Envelope Glitch Feature: The microprocessor responsible for generating the digital envelopes on the SX-240 runs on a unique clock cycle that can produce incredibly snappy attack times. When the Attack parameter is set to absolute zero, the hardware triggers the analog filters so abruptly that it produces a distinct, percussive electrical click transient. Sound designers frequently exploit this glitch to create ultra-sharp synth basses, analog congas, and synthetic rimshots.
An Advanced Real-Time Clock Workstation: For a non-workstation synthesizer in 1984, the SX-240 possessed a remarkably advanced onboard 1,500-note multi-track sequencer. Not only could it record and play back polyphonic patterns, but it also utilized an internal real-time memory backup system that preserved sequences even when the machine was powered down, allowing gigging musicians to carry custom synth sequences from the studio straight to the stage without needing external hardware disks.