The Maxon AF-9 Auto Filter is a Maxon envelope filter pedal, currently around $263.83. Close alternatives include the Subdecay Proteus MKII Sample and the Ashdown Type 23 Three Band Filter. It pairs well with the Park P50 Classic and the Bad Cat Cub.
Maxon AF-9 Auto Filter
Maxon · pedal
The Maxon AF-9 Auto Filter is an analog envelope filter that opens and closes an optical photocoupler filter in response to pick attack, producing the warm, vowel-like, liquid and shimmering sweep associated with vintage units like the Mu-Tron III. It offers low-pass, band-pass, and high-pass filter modes with switchable direction, plus threshold and peak controls that shape how quickly and how far the filter sweeps. Two selectable frequency ranges let it track both guitar and bass cleanly. It is closely associated with funk and soul playing, where its liquid, three-dimensional quacking response reacts directly to how hard notes are picked, and it remains a favored alternative to pricier vintage envelope filters for players chasing that vowel-like auto-wah character.
What stands out
“The Maxon AF-9 Auto Filter is an analog envelope filter that opens and closes an optical photocoupler filter in response to pick attack, producing the warm, vowel-like, liquid and shimmering sweep associated with vintage units like the Mu-T…”
— from the listing
“Two selectable frequency ranges let it track both guitar and bass cleanly”
— from the listing
“While the controls may initially appear daunting, they are thoughtfully laid out, with sliders for sensitivity and peak, and a frequency range switch that simplifies adjustments”
— from the reviews
“It is closely associated with funk and soul playing, where its liquid, three-dimensional quacking response reacts directly to how hard notes are picked, and it remains a favored alternative to pricier vintage envelope filters for players ch…”
— from the listing
“[Pros] ✓ Versatile across bass and guitar, enhancing live performances ✓ Adds a funky, organic sound reminiscent of Mu-Tron III ✓ Capable of boosting signal while modifying EQ, resonance, and harmonics ✓ Offers a slight boost and filter eff…”
— from the reviews
- filter
- bass
- peak
- frequency
- envelope
- vintage
- optical
- lead guitar
Price updated Oct 23, 2026
Genres the Maxon AF-9 Auto Filter is commonly used in
- Funk
- Alternative Rock
- Metal
- Soul
- Experimental
cited
Inferred from shared tonal signals, not a stated genre tag. - Electronic
cited
Inferred from shared tonal signals, not a stated genre tag.
Amps that pair well with the Maxon AF-9 Auto Filter
Park P50 Classic
Park
31% matchshapes the dynamic responseShapes how the tone responds to picking dynamics rather than its frequency or gain. (dynamic → compressed)
Park P50 Classic's own compressed character is the real reason this is worth trying
Comes later in the signal chain
Bad Cat Cub
Bad Cat
26% matchshapes the dynamic responseShapes how the tone responds to picking dynamics rather than its frequency or gain. (dynamic → compressed)
Bad Cat Cub leans toward harmonically rich, and that's a real, usable character to pair with
Comes later in the signal chain
Ceriatone British Style 2525
Ceriatone
tonal matchComes later in the signal chain
Put Ceriatone British Style 2525 after Maxon AF-9 Auto Filter
Vox AC30S1 OneTwelve 30W 1x12 Combo
Vox
tonal matchComes later in the signal chain
Put Vox AC30S1 OneTwelve 30W 1x12 Combo after Maxon AF-9 Auto Filter
Fryette Power Station 100
Fryette
tonal matchComes later in the signal chain
Fryette Power Station 100 goes after Maxon AF-9 Auto Filter in the chain
Kustom HV30 Tube
Kustom
tonal matchComes later in the signal chain
Kustom HV30 Tube goes after Maxon AF-9 Auto Filter in the chain
Mesa/Boogie Stiletto Deuce Stage II
Mesa Boogie
tonal matchComes later in the signal chain
Mesa/Boogie Stiletto Deuce Stage II goes after Maxon AF-9 Auto Filter in the chain
Friedman PT-20
Friedman
tonal matchComes later in the signal chain
Friedman PT-20 goes after Maxon AF-9 Auto Filter in the chain
Pedals that stack with the Maxon AF-9 Auto Filter
Origin Effects RevivalDrive
Origin Effects
25% matchshapes the dynamic responseShapes how the tone responds to picking dynamics rather than its frequency or gain. (dynamic → compressed)
Origin Effects RevivalDrive leans toward dynamic, and that's a real, usable character to pair with
Comes later in the signal chain
Dunlop MXR Distortion Plus
Dunlop
24% matchshapes the dynamic responseShapes how the tone responds to picking dynamics rather than its frequency or gain. (dynamic → compressed)
What Dunlop MXR Distortion Plus brings here leans toward warm — that's worth building a pairing around
Comes later in the signal chain
JHS Lucky Cat Delay limited edition
JHS Pedals
13% matchsits in the right chain slotPlaced for where it does its job cleanly in the chain, not for a tonal interaction with the anchor.
Keep JHS Lucky Cat Delay limited edition after Maxon AF-9 Auto Filter in the signal chain, where it won't crowd Maxon AF-9 Auto Filter — goes in the amp's FX loop (or last, into a clean amp)
Comes later in the signal chain
Keeley Halo
Keeley
12% matchsits in the right chain slotPlaced for where it does its job cleanly in the chain, not for a tonal interaction with the anchor.
Keep Maxon AF-9 Auto Filter's analog warmth voice out front: Keeley Halo goes after Maxon AF-9 Auto Filter in the signal chain so its ambient voice doesn't muddy it — goes in the amp's FX loop (or last, into a clean amp)
Comes later in the signal chain
DigiTech DOD Compressor 280
Digitech
tonal matchComes later in the signal chain
DigiTech DOD Compressor 280 goes after Maxon AF-9 Auto Filter in the chain
DigiTech XBS Bass Squeeze
Digitech
tonal matchComes later in the signal chain
DigiTech XBS Bass Squeeze goes after Maxon AF-9 Auto Filter in the chain
Fairfield Circuitry 20% More
Fairfield Circuitry
tonal matchComes later in the signal chain
Fairfield Circuitry 20% More goes after Maxon AF-9 Auto Filter in the chain
Tech 21 CompTortion
Tech 21
tonal matchComes later in the signal chain
Put Tech 21 CompTortion after Maxon AF-9 Auto Filter
Cheaper alternatives
Carl Martin Ottawa
Carl Martin
69% similarityShared character: soul, sensitivity, natural resonance
Carl Martin Ottawa Vintage Optical Envelope Auto-Wah/Envelope Filter
Carl Martin
68% similarityShared character: soul, sensitivity, natural resonance
Electro-Harmonix XO Micro Q-Tron
Electro-Harmonix
67% similarityShared character: peak, sensitivity, natural resonance
Electro-Harmonix Nano Q-Tron
Electro-Harmonix
65% similarityShared character: peak, sensitivity, natural resonance
Dr. Scientist Dusk
Dr Scientist
62% similarityShared character: natural resonance, analog, filter
Electro-Harmonix Riddle Q Balls
Electro-Harmonix
62% similarityShared character: soul, peak, sensitivity
Boutique & premium upgrades
Fairfield Circuitry Long Life
Fairfield Circuitry
67% similarityShared character: peak, natural resonance, analog
Spaceman Artemis Modulated Filter
Spaceman
52% similarityShared character: filter
Pigtronix Resotron Analog Tracking Filter
Pigtronix
94% similaritysimilar tone character
Similar charactersee all similar tone character →
Subdecay Proteus MKII Sample
Subdecay
58% similarityShared character: natural resonance, filter, pick attack
Ashdown Type 23 Three Band Filter
Ashdown
55% similarityShared character: soul, live performances, sensitivity
Empress Para EQ DLX
Empress
54% similarityShared character: filter
Emma DiscomBOBulator
pedal
54% similarityShared character: controls, soul, sensitivity
Guyatone Wah Rocker WR3
pedal
94% similaritysimilar tone character
Keeley Neutrino V2
Keeley
94% similaritysimilar tone character
See all alternatives to the Maxon AF-9 Auto Filter (cheaper + boutique) →
Questions people ask
What are good alternatives to the Maxon AF-9 Auto Filter?+
The closest matches in character are the Subdecay Proteus MKII Sample, the Ashdown Type 23 Three Band Filter, the Empress Para EQ DLX. Budget picks: Carl Martin Ottawa, Carl Martin Ottawa Vintage Optical Envelope Auto-Wah/Envelope Filter, Electro-Harmonix XO Micro Q-Tron. Boutique upgrades: Fairfield Circuitry Long Life, Spaceman Artemis Modulated Filter, Pigtronix Resotron Analog Tracking Filter.
What pairs well with the Maxon AF-9 Auto Filter?+
Strong matches from rig and tone-complementarity evidence: Park P50 Classic, Bad Cat Cub, Ceriatone British Style 2525 — Park P50 Classic's own compressed character is the real reason this is worth trying.
How much does the Maxon AF-9 Auto Filter cost?+
Around $263.83 (live listing price, updated Oct 23, 2026).