Maxon AF-9 Auto Filter


  • Sensitivity
    determines when the effect will trigger.
  • Peak
    boosts the center frequency for more dramatic filtering (like a Resonance control on a synthesizer).
  • Filter (LP/BP/HP)
    Selects the type of filter: Lowpass, Bandpass or Highpass.
  • Drive (Up/Down)
    Selects the direction of the filter sweep: upwards or downwards.
  • Range (High/Low)
    Selects the frequency range of the filter.



The AF-9 Auto Filter represents the state-of-the art in analog filtering. Like the original Mutron III, the AF-9 uses a CdS Photocoupler (HTV #P873) rather than a VCA at the heart of its circuit. The unique sound of Photocoupler circuitry provides a liquid, shimmering, vowel-like filtering that cannot be produced with other components, giving the AF-9 superior sound quality with lower noise levels than the competition.

The AF-9's Threshold control determines when the effect will trigger, while the Peak control boosts the center frequency for more dramatic filtering (like a Resonance control on a synthesizer). Selectable Range control (Hi/Low) determines the overall tone of the AF-9, while the Drive (Up/Down) control determines the direction of the filter sweep. Three selectable Filter types (Hi Pass, Band Pass, and Low Pass) and a frequency range of 100 Hz Ð 4 KHz allow the AF-9 to function with virtually any instrument or input signal.

From simple wah-wah's to outer-space noises, the AF-9 provides the most desirable swept filter effects in a compact, user-friendly package.

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  • Input Impedance
    500K Ohms
  • Output Impedance
    10K Ohms
  • Residual Noise
    -95 dB or less (input shorted IHF-A weighted)
  • Filter Frequency
    100 Hz ­ 2 KHz (Low) / 200 Hz ­ 4 KHz (High)
  • Power Voltage
    DC9 V (Battery) / DC10 V (AC-adaptor)
  • Current Consumption
    17 mA (9 V) / 19 mA (10 V)
  • Dimensions
    74 mm (W) x 124 mm (D) x 54 mm (H)
  • Weight


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