WMD QAAF Quad Anti-Aliasing Filter - 4HP

WMD QAAF Quad Anti-Aliasing Filter 4HP

WMD QAAF is a compact four-channel analog filtering module designed to remove aliasing, stepped digital artifacts and unwanted high-frequency content from Eurorack signals. Originally developed as an expansion for the WMD Phase Displacement Oscillator, QAAF can also operate completely independently as a versatile pre- or post-processing filter bank.

Each of the four channels uses a 4-pole switched-capacitor Butterworth low-pass filter with closely matched cutoff frequencies across all channels. The module provides individual audio inputs and outputs for all four filters along with a Mix output that sums the four filtered signals.

A shared CV input controls the filter frequencies and is approximately calibrated to 1V/octave. The Frequency control provides manual cutoff adjustment and also acts as an offset for incoming CV. The CLK connection can operate as either a clock input or output and directly controls filter frequency at a 100:1 relationship, with the operating mode selected using a rear-panel jumper.

A second rear jumper can limit the minimum cutoff frequency to approximately 300Hz, preventing the QAAF's switched-capacitor clock from entering the audible range. Its fully analog architecture, compact 4HP footprint and four independent channels make QAAF useful not only for anti-aliasing but also for smoothing digital waveforms, filtering modulation-derived audio and general multi-channel low-pass processing.

• Four independent analog low-pass filters
• Designed for anti-aliasing and waveform smoothing
• Originally designed as a WMD PDO expansion
• Can operate independently as a standalone filter module
• 4-pole filter architecture
• 24dB/octave response
• Butterworth response curve
• Switched-capacitor filter design
• Approximately ±0.5% channel-to-channel frequency matching
• Four individual audio inputs
• Four individual audio outputs
• Mix output sums all four filtered channels
• Shared CV frequency control
• CV input approximately calibrated to 1V/octave
• Frequency offset control
• Configurable clock input or output
• 100:1 clock-to-filter frequency relationship
• Rear low-frequency limit jumper
• Approximately 300Hz minimum cutoff when limiter is enabled
• PDO expansion header
• Suitable for pre- and post-filtering applications
• Fully analog signal path
• 4HP Eurorack format
• 40mm module depth
• +12V power consumption: 35mA
• -12V power consumption: 35mA