Best Envelope Filter Pedals – For Turning on the Funk

Often using a wah-wah pedal is impractical during live performance. Having to rock your foot back and forth to get that “quack” or “bow wow” sound, plus playing the guitar and maybe even singing at the same time – it’s a total juggling act.

Worse still, concentrating on your wah too much can detract from your performance. Balancing on one leg whilst you wah with the other might not be the look you’re going for on stage.

a selection of electro-harmonix pedals, including an envelope filter pedal

Fortunately, there is help at hand. A device called an envelope filter pedal – sometimes referred to as an ‘auto wah’ – lets you get the wah without having to lift a finger (well, lift a toe). These pedals allow you to achieve a funky wah sound on autopilot. Plus, they’re superb for experimentation as we’ll see. If you’re in a rush, here’s a quick peek of the products we review further down the page:

At a Glance: Our Choice of the 5 Best Envelope Filter Pedals on the Market


Electro-Harmonix Q-Tron Plus XO Envelope Follower Pedal

Electro-Harmonix Q-Tron
  • Used by Bootsy Collins and George Clinton
  • Multiple modes, boost and gain controls

Electro-Harmonix Riddle: Q-Balls for Guitar Envelope Filter

Electro-Harmonix Riddle: Q-Balls
  • Upgrade from the Q-Tron
  • Analog circuitry
  • Input for an expression pedal

Source Audio SA127 Soundblox Guitar Envelope Filter

Source Audio SA127​
  • Ultra-compact design
  • Excellent value for money
  • 21 filter options

Pigtronix EP2 Envelope Phaser Guitar Effects Pedal

Pigtronix EP2​
  • LFO option
  • Two inputs for expression pedals
  • Staccato switch

Maxon 9-Series Auto Filter

Maxon 9-Series Auto Filter
  • Built like a tank!
  • Nice warm Jerry Garcia tone
  • True bypass

In this article we’re going to go deep into the what, why and how of these pedals. By the end of it you’ll know exactly how they can transform your playing. We’ll also recommend some of favourite units on the market. Sound good? Let’s get to it…

What is an Envelope Filter?

A filter is a bit of circuitry that adjusts the ‘shape’ of all frequencies that come through it. We’re all familiar with EQ (‘Equalisers’) you find on car stereos. Well, that’s a filter.

But usually when people talk about filters they mean effects like a wah or an envelope filter. These have much stronger tone changes than just a regular EQ. The key difference is they also use what’s known as ‘resonance’ to accentuate certain frequencies, thereby creating the sort of sounds we associate with wah or funk – that distinct “quack” and “bow wow” sound. So what about the envelope? Well the “envelope” is the shape of each note you play, from the initial spike when you pluck or pick a note, through to the moment it trails off.

How Does an Envelope Filter Pedal Work?

In essence they give you the ‘wah sound’ you’d normally get from a wah pedal, with one key difference: the wah sound is triggered by how hard you play (i.e. how hard you pluck your strings, also called ‘your attack’) rather than having to rock your foot as you do on a normal wah pedal. The harder the attack, the more it goes ‘wah’.

These units are mostly used in funk music for that signature “quack” or “bow wow” sound and can be used the bass, guitar, or keyboards.

Features You’d Expect to Find On One of These Pedals

Envelope filters come in many shapes and sizes, some are ‘set it and forget’ pedals and the more advanced ones give you a ton more features, letting you tweak various parameters. Here are the most common features you’ll find:

  • Range (Sweep) Control
  • Filter or Mode Control
  • Attack/Response and Decay Control(s)
  • Resonance Control
  • Sensitivity Control

Range (Sweep) Control

The Range control adjusts the frequencies which are affected by the ‘sweep’ effect. This means that you can have more of the effect when you’re playing high notes than when you’re playing low notes, or vice versa. It can be very handy: you might not want wah on every single note you pick hard.

Filter or ‘Mode’ Control

Some pedals call it ‘Filter’, which others call it ‘Mode’, but it’s the same thing. It lets you choose between a low-pass, high-pass or band pass filter. These filters pick out certain frequencies: a high-pass filter lets anything above a certain frequency get through, the low-pass lets anything below a certain frequency through, and the band-pass puts a band in the middle and anything either side of it gets through.

Attack/Response and Decay Controls

Some pedals include an Attack control (some models call this Response). The Attack controls how quickly a sweep peaks. The decay control determines how soon it cuts out. A fast attack and a slower decay will provide a clear, rhythmic sound. Slower attacks can make your playing sound out of time, and decays which are too fast can also detract from the rhythm of your playing.

Resonance Control

The Resonance Control lets you adjust the feedback of the filter. This allows you to set certain frequencies to amplify more than other frequencies. It can be the control that helps you to achieve a sharp, almost distorted tone, or a mellow, laid back tone.

Sensitivity Control

The sensitivity control adjusts the response of the pedal according to your pick attack. If you’re a heavy player anyway, you’ll want to set this quite low. Gentle players, you’ll need high sensitivity. If you mix things up a bit, depending on what you’re playing, you’ll really see the benefits of having this control on your pedal.

What are the Benefits to These Pedals?

So we’ve already touched on one of the biggest reasons why you’d want to get an envelope filter pedal, namely convenience. But there are some other less obvious reasons you may want to try one out.

Set it and Forget it

Pretty much what we’ve covered. Envelope filter pedals do what normal wah pedals do, but don’t need to be controlled as you play. For this reason they’re a ‘set it and forget it’ option as opposed to a traditional wah pedal, that needs a bit of footwork to work.

Faster Wahing

This is one of the main reasons people opt for envelope filters over traditional wah pedals. The circuits within these pedals can react at a faster rate than we can physically move our feet, making a rapid wah-wah-wah-wah sound possible. This effect is really common in funk music. As well as being capable of a faster speed than your foot can manage, the fact that it’s automatically controlled means that the rhythm of the sweeping will sort itself out.


It’s a bit like driving a manual (stick shift car) versus an automatic. Driving a stick shift gives you more ‘control’, but really do you need that control? Perhaps your attention is better placed elsewhere (i.e. on your guitar playing or singing). Don’t think for a minute that these pedals ‘dumb down’ your sound either – the Range control (see above)  makes the pedal very responsive, so the harder you pick the more wah you get (the louder the picking, the higher the tone).

Light and Compact

Envelope filter pedals are also a lot smaller and lighter than your standard wah pedals, so they fit into your pedal boards more easily. If you’re a travelling musician, this can make your load a lot easier to manage than if you use a traditional wah pedal. The simpler ‘set it and forget it’ models are really compact.

Who Uses Them?

As mentioned, envelope filter pedals are common in funk music, particularly amongst bass players including the legendary Bootsy Collins. Or think about the 1970’s Jerry Garcia guitar mutron sound? That’s using one of these pedals. Check out the guitar is in The Who’s ‘Going Mobile’ (the guitar solo around 2 minutes in!). It’s also one of the many things that makes Prince’s ‘Cream’ such a brilliant track.

Buyer’s Guide – Considerations When Buying an Envelope Filter

Do You Need it for a Bass Guitar or a Guitar?

You should be aware of whether the envelope filter you’ve just picked out is voiced for bass or guitar. Some are designed for lower frequencies, i.e. bass guitars. Indeed, envelope filters are more commonly used in the bass world than by guitarists. Our product reviews lean towards envelope filters designed for guitarists.

Stomp Box Vs Additional LFO

These pedals come in mainly two formats:

  • Stomp box style pedal. These are small pedals which fit into your pedal boards. They tend to be easy to use and to adjust, and the best ones come in sturdy metal casing and have multiple controls. These will suit those who know what they want and like to keep things simple.
  • Pedals with additional LFO. These tend to be slightly bigger than stomp box sized pedals, and are well suited to those who like to keep their tonal options open. LFO (low-frequency oscillation) means that, rather than using an envelope detector to detect your volume, a low-pass or bandpass filter is used to detect the frequencies. 

Matching The Pedal To Your Musical Style

Some envelope filters are designed with disco or funk in mind, whereas some are built with a broader purpose. If all you want to do is funk, it makes sense to go for one that’s purpose-built for it. If you’re aiming for something more versatile, hunt out one with extra options.

Built in Effects

Other pedals have built in phasers or delay effects. If you’re in the market for a phaser or delay, you can save yourself some money and get those effects as part of your pedal. These can be convenient and fun, and can provide you with some exciting creative options.

True Bypass

True bypass allows an input to lead to an output without any interference or buffering when the pedal is switched off. This is worth having in any pedal, as it prevents unwanted buzzing when you’re not using the effect.

Optional Battery

It can be handy to have a battery option in a pedal, especially if you’re planning on planning on playing outdoors. However, there is often no need for a battery option in your guitar pedals. If you’re playing on a stage, with multiple pedals, your best bet is to plug them all into a multi-adapter and plug in on stage. This is better for the environment, too.

Where to Place it in Your Signal Chain?

There’s no right or wrong way to position an envelope filter pedal. How you do so will be largely a personal preference. However, there are two main ways to do it. A lot of guitarists choose to have their pedal at the start of their chain – right next to their guitar. This enables a clean signal to reach the pedal, which is helpful as it’s responding to your picking attack.

Other guitarists prefer to have their wah pedals at the end of their chain – closest to the amplifier. This can be interesting as it means that other effects can potentially affect the signal going to the envelope filter, producing some interesting and original sounds.

Product Round-up & Mini Reviews

Electro Harmonix Q-Tron

Electro-Harmonix Q-Tron Plus XO Envelope Follower Pedal

This is one of the most popular, and is often held to be one of the best envelope filter pedals around, thanks to its iconic tone. It’s used by Bootsy Collins and George Clinton, and has all of the essential features and more. There are multiple modes, boost and gain controls, and even a peak knob to give you control over the width of your sound.  Newer models contain an effects loops, so that you can insert an additional effect between the pedal’s pre-amp and filter. This makes the pedal more responsive to your playing and gives you more sound options.


  • Four filter modes, speed, volume and intensity settings give you plenty of options for fine-tweaking and adjusting the character of the filter
  • It’s solid and rather cool looking: it holds to its funk and disco roots in aesthetics as well as its tone.
  • Contains true bypass, so it won’t interfere with your signal when it’s not in use.
  • Built in effects loop


  • Although the four filter modes are pretty great, some models offer more than this.
  • No expression-pedal options so you’ll need to set-and-forget this pedal.
  • Although not expensive by any measure, it doesn’t provide the best value for money



Electro-Harmonix Riddle: Q-Balls

Electro-Harmonix Riddle: Q-Balls for Guitar Envelope Filter

Is it just me or do these pedals all seem to have silly names? Regardless, this is an upgrade from the Q-Tron, so take everything you liked about that pedal, and prepare for a little more. The best thing is that this pedal is only fractionally more expensive, but provides much better value. It features multiple modes, attack, decay, blend and sensitivity knobs, but it also has two controls which weren’t seen on the Q-Tron. There are stop and start knobs here which allow you to set the starting and ending points of the sweep. This gives you an excellent amount of controllability and makes the pedal amazingly versatile. It’s also in sturdy, chrome casing: made for taking on the road.


  • All the circuitry is analog, which helps to keep the 70’s sound alive (who said disco is dead?) and doesn’t interfere with your signal if this is part of a chain
  • There’s an input for an expression pedal giving you more intimate control of the filter’s sweep direction and depth
  • Controls for attack, decay, sensitivity and Q (how many frequencies are affected by the envelope pedal’s settings), as well as additional stop/start knobs to set the size of the sweep.


  • Has one less filter compared to the Q-Tron
  • The filter options which are available aren’t particularly creative, so if you were looking to experiment beyond the classic sounds of envelope filter pedals you’ll be disappointed by the lack of options
  • It’s a rather basic design, and the small size of the dials can make it difficult to see the settings if you need to change them under poor lighting (which as well know can be a real pain for a gigging musician)



Source Audio SA127

Source Audio SA127 Soundblox Guitar Envelope Filter

The SA127 delights in playing with the old adage that less is more. You get enough variety to play around with forever, but it’s all contained in an ultra-compact design. In keeping with the disco roots, it’s bright purple. It’s also excellent value for money, especially when compared to either of the Electro-Harmonix models. There are 21 filter sounds, an attack and decay control and a knob to set the size of the sweep. Although it’s small, you still have quite a lot of control over your sound with this pedal.


  • An unholy array of choices, you get 21 filter options all controlled by a single dial
  • Three additional dials for controlling attack, decay, sweep, range and sensitivity
  • The whole pedal has a remarkably slim profile considering all of the options available, meaning it’ll fit snugly on any pedal board


  • Many of the controls are merged together. Although this works quite well most of the time thanks to the way they’ve been paired up, it can limit your options
  • No expression pedal options, so you will have less intimate control.
  • Since the controls are combined into just four dials, you’ll have to spend a little time learning how they all work together in order to ensure the best results, unlike with other models where you can play with one setting at a time to learn its ins and outs




Pigtronix EP2

Pigtronix EP2 Envelope Phaser Guitar Effects Pedal

Possibly the worst looking pedal so far, don’t let that put you off. It’s a little more expensive than the others, but also comes with some extremely great features that set it above more basic varieties of envelope filter pedals with ease. It has an LFO option, so you can control your auto-wah sounds using either the envelope filter or the low-pass filter. This gives you more options for controlling the response of the pedal: it can follow dynamics or be time operated. You can even use the both together, for some very interesting sounds. This pedal also has a staccato function which adds extra response to the envelope. Very well suited to playing funk.


  • Has not just one, but two inputs for expression pedals that allow you to control speed and sweep direction seperately, plus an input for a “trigger” that allows the envelope filter to be controlled by other external sources.
  • The Staccato switch enables the filter to adjust to every note even when playing at inhuman speeds to ensure perfect articulation even if you decide to bust out the shredding and sweep-picking. Could this be the envelope filter for metalheads? Just maybe!
  • Has some truly fantastic tone, which you can endlessly play with thanks to the huge range of controls


  • Although you get a lot in one package, this pedal is quite expensive and if all you need is the standard funk/disco sound, you would do better to look at some of the simpler pedals available
  • The complexity of the controls might take a while to get used to (have you ever tried to use two expression pedals at once? It can end spectacularly badly when you forget which is which)
  • It uses an 18v battery, which gives great headroom, but can put a bit of dent in your bank account as this thing runs through juice like you wouldn’t believe if you can’t use a mains power supply or a rechargeable battery



Maxon AF-9

Maxon 9-Series Auto Filter

This filter takes a straightforward approach to give you a no-fuss answer to your envelope filter pedal needs. It looks a bit retro, but considering the sound it produces, perhaps that’s in line with what it should be. There are filter, range and drive switches, as well as sensitivity and peak controls. Although it’s small, you can still control quite a lot. It also features true bypass, so it won’t muddy your signal when it’s not in use.


  • Built like a tank. There’s very little that’s vulnerable to damage, and it can safely be carried around from venue to venue with no problems at all for years. It can even take a hell of a beating, making it live up to the stomp part of “stompbox”
  • True bypass means it won’t ruin your tone when not in use
  • Nice warm tone that closely resembles the legendary Jerry Garcia sound that gets people interested in envelope filter pedals for the first time more often than not


  • It’s a basic pedal, lacking some of the extended functionality and fine tuning controls of more advanced models
  • It’s quite expensive for the simplicity of the pedal
  • No expression pedal input available, so it does lack the option for intimate control



So Which Should I Buy?

So, the question still stands, which is the best envelope filter pedal?

It depends on why you’re looking to get one, if you just want that classic 70s bow-wow cheesy porno sound, then you’re in luck as all 5 mentioned today are more than capable of doing that. But chances are you’ll want to fine-tune it to either mimic the greats exactly or get your own signature sound.

For this reason, the Pigtronix EP2 and the Source Audio SA127 should be the top of your list. The EP2 offers a lot of fine tuning, and the two expression pedal jacks really put all of the control you could ever want in your hands (and feet), but if you find all of the options a bit overwhelming and would rather just dive in, then the SA127 might be more your style thanks to its merged controls and massive range of filters for quick exploration.

Have you had one or more of these pedals? Let us know which is your favourite, and why, in the comments below. If you’ve got another that we didn’t mention, don’t hesitate to get involved. Sadly we don’t have room for every pedal out there, so take the chance to help out your fellow musicians!


Featured image Courtesy of Richie Adiyat / CC BY-SA 2.0

Ged is Founder and Editor-in-chief at Zing Instruments. He’s a guitarist for London based gypsy jazz band ‘Django Mango’ and a lover of all things music. When he’s not ripping up and down the fretboard, he’s tinkering with his ’79 Campervan.

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