Change Log
Aprés Dix LA Circuits Eurorack
Voltage-Controlled Multi-Band Filter
Traditional subtractive filters shape sound by selectively removing harmonic content. APRÈS DIX takes a more expansive approach, combining precise tonal control with the expressive behavior of a dynamic acoustic resonator.
Rather than simply attenuating selected frequencies, it actively shapes harmonic character, responds to percussive excitation, and sustains resonant tones.
The EM-402 is a high-precision voltage-controlled multi-band filter designed around an active state-variable topology. Combining classical laboratory functionalism with rigorous electroacoustic engineering, it provides four simultaneous response outputs: High-pass, Band-pass, Notch, and Low-pass.
At the core of the circuit lies a matched set of THAT2181-A ICs, complemented by high-performance OPA-series operational amplifiers. Selected for their exceptionally low distortion, wide dynamic range, and minimal control-voltage feedthrough, these components maintain precise gain staging and signal integrity throughout the filter architecture. Under heavy feedback, the dual-input configuration balances controlled gain compensation with unattenuated saturation, preserving fundamental weight and dynamic presence even at extreme resonance settings.
Multiple resonant feedback paths provide exceptional sustain, allowing the filter to develop prolonged, harmonically rich oscillations and naturally decaying resonant tones. As resonance approaches self-oscillation, the core blooms with increasing harmonic complexity while preserving low-frequency energy and tonal definition. Direct voltage control over the resonance factor through the dedicated CV / Q input enables dynamic modulation of the resonance peak and bandwidth independently of the primary cutoff frequency.
Pre-filter signal mixing is handled through two independent input channels with dedicated gain controls, allowing incoming signals to drive the processing core into variable harmonic overdrive before distribution across the four simultaneous filter outputs.
The control interface provides three distinct frequency-modulation paths: a calibrated 1V/Oct input, a variable exponential FM input, and a dedicated STRIKE input incorporating an internal fast-decay modulation envelope. The exponential FM input features a bipolar Depth Polarizer attenuverter for continuous modulation across positive and negative control-voltage polarities.
Particularly notable is the circuit's exceptional responsiveness to percussive excitation. Incoming triggers at the STRIKE input activate a short, snappy envelope routed directly to the filter's frequency-modulation circuitry, eliminating the need for an external envelope generator.
Combined with the sustained energy of its multiple resonant feedback paths, this arrangement transforms APRÈS DIX into a highly expressive percussive instrument, capable of producing everything from deep, rounded bass drums and tight woodblock strikes to articulate mallet tones, metallic bells, and prolonged resonant decays. Subtle adjustments to frequency and resonance yield considerable variation in attack, harmonic character, and sustain.
01 / CIRCUIT ARCHITECTURE
Model — EM-402 APRÈS DIX
Type — Voltage-Controlled Multi-Band State-Variable Filter
Architecture — Analog, THAT2181-A VCAs / OPA-Series Operational Amplifiers
02 / SIGNAL INTERFACE
Audio Inputs — 2, with independent gain controls
Audio Outputs — High-Pass / Band-Pass / Notch / Low-Pass (simultaneous)
Frequency Modulation — 1V/Oct / Variable Exponential FM / STRIKE
03 / RESONANCE & EXCITATION
Resonance — Voltage-Controlled, Self-Oscillating
STRIKE — Internal Fast-Decay FM Envelope
04 / PHYSICAL SPECIFICATIONS
Power Supply — Eurorack ±12V
Panel — Anodized Aluminum
LA CIRCUITS, INC.
Official Website — https://circuits.audio
Instagram — https://instagram.com/lacircuits
Email — contact@circuits.audio
- 50 mA +12V
- 50 mA -12V
- ? mA 5V
- 29 mm Depth
This Module is currently available.
$450