Originally introduced as a key component of analog synthesizers, envelope controlled filters came into prominence in the early 1970s with the release of the legendary Mutron III. Envelope filters are wah-wah type sliding filters that are triggered by an input voltage. Unlike standard wah pedals whose center frequency is controlled by moving a treadle, an envelope filter's center frequency is controlled by playing dynamics, allowing for an almost unlimited variety of effects based on expressive nuances in a player's performance.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.FeaturesThe coolest aspects of auto-wah and swept filter effectsOpto-coupler circuitry produces vintage shimmering, watery filtering effectsThreshold and peak sliders control the degree of effectRange and drive switches determine range and direction of filter sweeps3 selectable filter types: Lo Pass, Band Pass, and Hi Pass100Hz-4kHz range for staggering effects with any instrument or input signalTrue bypassDie-cast zinc case3-year warrantyAC/DC operation (order optional Maxon AC210N adapter)We are an authorized Maxon dealerInternational Buyers – Please Note:•Import duties, taxes and charges are not included in the item price or shipping charges. These charges are the buyer’s responsibility.•Please check with your country’s customs office to determine what these additional costs will be prior to looking/buying.•These charges are normally collected by the delivering freight (shipping) company or when you pick the item up – do not confuse them for additional shipping charges.•We do not mark merchandise values below value or mark items as ‘gifts’ - US and International government regulations prohibit such behavior. _gsrx_vers_454 (GS 6.3 (454))