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Teisco SX-400 - Image 1

Teisco SX-400

KeyboardAnalogPolyphonic

Back in the early '80s, this synth punched way above its budget weight class by packing four independent analog oscillators into a keyboard instrument that could go from polite polyphony to monstrous mono leads, all while offering memory storage that was pretty forward-thinking for the era.

At its core, it delivers four voices through independently tunable VCOs, each with multiple waveforms like sawtooth, ramp, square, and triangle, routed through a shared filter and a single envelope generator for the VCF, plus another EG for the VCA. You'll find a swarm of sliders for hands-on control over everything from LFO modulation—two of them, one with delay and shape options—to cutoff, resonance, and amplitude, with aftertouch and a pitch/mod wheel that can simultaneously bend pitch, vibrato, and filter sweep. The 32-key dynamic keyboard feels responsive, and modes let you switch between quad poly, dual, or single-oscillator mono mayhem. It's a hefty desktop beast with stereo outputs for its built-in Ensemble chorus, pro-level +4dBm option, and 8 factory plus 8 user patches stored in internal memory.

Players have long praised its thick, warm analog tone—often stacking those VCOs for Juno-like depth with more expressive control—and the hands-on slider layout that invites tweaking, though some note its large footprint demands serious desk space.

Released

1981

Status

Discontinued

Synthesizer
Format
Keyboard
Type
Subtractive
Internal Battery
-
Voice
A/D
Analog
Polyphony
Polyphonic
Oscillators
4
Oscillator Type
VCO (Voltage Controlled)
Voices
4
Filter
Lowpass, 24dB/oct (4-pole), Resonant
Envelopes
2
LFO
2
Effects
Ensemble (chorus), Portamento
Expression
Aftertouch
-
Velocity
-
MPE
No
Additional
-
Software
-
I/O
Audio In
-
Audio Out
2x 1/4" jack (L/R)
Headphone
1x stereo phones
MIDI
-
MIDI Type
-
Ports
CV/Gate, Expression Pedal, Gate In
Wi-Fi
No
Workflow
Arpeggiator
-
Sequencer
-
Mod Matrix
-
Memory
8 factory, 8 user
Measurements
Dimensions
-
Weight
-
Last updated Mar 24, 2026