Nine Series Effects Pedals

maxon nine series guitar effects pedalsSince their introduction in the early 1980s, Maxon Nine Series designs have achieved a legendary status with pedal connoisseurs around the globe. The reasons for this are simple - superior sound quality and innovative features that offer a seamless interface between performer and performance. 20 years later this rule still holds true. Now available with improved circuitry including JRC4558 IC chips and True Bypass Switching, Maxon Nine Series effects remain the standard by which all others are judged.

AF-9 Auto Filter


More Info

Maxon’s take on the legendary Mu-Tron III, the AF-9 Auto Filter uses special optical circuitry to reproduce the liquid, shimmering, vowel-like envelope filtering that made the Mu-Tron a staple of 70’s Funk and Soul music.

The AF-9's intuitive user interface makes it easy to dial in the effect – slider pots are used for Threshold and Peak controls to allow for quick changes to the response and tonality of the filter.

The Threshold control determines the degree of pick attack needed to trigger the filter.

The Peak control boosts the center frequency of the filter to emphasize the filtering effect (think Resonance control on a synthesizer).

The Range switch determines the overall frequency where the filter sits, while the Drive switch determines the direction of the filter sweep – low to high or high to low.

Three selectable Filter types (HP, BP, and LP) and a frequency range of 100 Hz to 4 KHz allow the user to dial in the AF-9’s wah effect with virtually any instrument or input signal.

From simple Wah to funked-up Outer Space explorations, the AF-9 provides the most delicious, delightful, diabolical wah filter effects available in a compact, user-friendly package.

Why Choose Maxon?

The AF-9 sounds like a vintage Mu-Tron III at a fraction of the price.

Tech Talk

The AF-9 is Maxon’s version of the venerable Mu-Tron III envelope filter circuit (original version, not HAZ reissue).  The biggest difference between the two circuits is that the AF-9 runs on a single 9V supply while the Mu-Tron ran at 18V.

In addition, the III had a Gain pot which controlled the output level of the pedal as well as the Threshold of the Filter – this was an awkward design, as it prevented increasing the filter sensitivity without raising the output volume of the pedal.

These items aside, the basic structures of the two circuits are very similar. The AF9 starts with a unity gain buffer Op Amp and then splits the signal into control and effected circuits. The control circuit is shaped by the Sensitivity pot and amplified by an Op Amp.  This control signal then travels to a series of two photocouplers.

The effected portion of the circuit split goes into a three Op Amp filter network that is almost identical to the Mu-Tron’s, right down to the Low Pass, Band Pass, and High Pass switch that selects which portion of the filter network is used.  These filters are triggered by the CdS cell side of the previously mentioned photocouplers.

The AF-9’s Range is selected by changing the gain structure of the filters.  After the filter network the signal is run through a unity gain buffer to provide a low impedance output.

The AF-9 features Mechanical True Bypass switching via a Fujisoku 4PDT switch.

Mods & Mends

Preamp Mod

Input Sensitivity Mod

What Artists Say…

Marty Friedman

Marty Friedman

ex-Megadeth, Cacophany

Erik Rutan"The Maxon Auto Filter is one of my favorite "go-to" pedals. This really helps you give your playing a human voice without sounding like you just stepped on an effects pedal. It is really special and you can hear it on tons of my recordings."


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AF-9 Demo
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Envelope Filter Comparison
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Pop Into the Chemist

AF-9 Auto Filter Review
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Maxon AF-9 Auto Filter Demo
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Brett Kingman

Maxon: AF-9, AD999, D&SII
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Auto Wah Pedal Demo - Maxon AF-9
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Marty Friedman

Hear Their Gear
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Danny Rader (Keith Urban) Demo
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Oz Noy AF-9 Demo
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Pimpin' Pedals



Input Impedance: 500K Ohms Input Jack: 1/4 inch standard phone jack Output Impedance: 10K Ohms Output Jack: 1/4 inch standard phone jack Output: 1 Residual Noise: -95 dB or less (input shorted IHF-A weighted) Filter Frequency: 100 Hz ­ 2 KHz (Low) / 200 Hz ­ 4 KHz (High) Controls: Sensitivity, Peak Switch: Normal/Effect (true bypass configuration), Filter LP/BP/HP, Drive Up/Down, Range High/Low Power Supply: 9V Manganese dry cell battery (6F22) or special AC adaptor Power Voltage: DC9 V (Battery) / DC10 V (AC-adaptor) Current Consumption: 17 mA (9 V) / 19 mA (10 V) AC Adaptor: AC210N (option) Input: AC120V Output: DC9V/200 mA Center - / Sleeve +) Dimensions (whole): 74 mm (W) x 124 mm (D) x 54 mm (H) Weight: 580 g Accessories: 9V Manganese dry cell battery (S-006P) x 1 Warranty Card: x 1 User's Manual: x 1 * All specifications are subject to change for improvement without notice or obligation. All brand names and product names are trademarks or registered trademarks of their respective companies.
  • Optical Envelope Filter ala’ vintage Mu-Tron III
  • Funky, liquid, vowel-like Wah effects
  • Low Pass, Band Pass and High Pass filters
  • Low and High operation ranges
  • Threshold and Peak sliders
  • Up/Down Drive switch
  • True Bypass Switching


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AF-9 Auto Filter
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46 Marlboro Rd., Clifton, NJ 07012
Godlyke Distributing