Envelope filter pedals (often referred to as an ‘auto-wah’) give you a wah sound without having to rock your foot back and forward on a wah-wah pedal. They are, unsurprisingly, hugely popular guitar pedals with funk players. 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 Best Envelope Filter Pedals on the Market
- Electro-Harmonix Q-Tron (Best Overall)
- Electro-Harmonix Micro Q-Tron (Best Budget)
- EarthQuaker Devices Spatial Delivery V2 (Best Premium)
- Source Audio SA127
- Pigtronix EP2
- Maxon 9-Series
Note: Clicking the above links will take you to further information, current prices and customer reviews on Amazon.
In this article, we’re going to go deep into these pedals. We’ll also recommend some of the favorite products on the market. Sound good? Let’s get to it.
Table of Contents
- What is an Envelope Filter?
- Buyer’s Guide – Key Considerations
- Product Round-up & Mini Reviews – Best Envelope Filter Pedal
What is an Envelope Filter?
Envelope filters have much stronger tone changes than say a regular EQ. They use what’s known as ‘resonance’ to accentuate certain frequencies, creating the sort of sounds we associate with wah or funk – that distinct “quack” and “bow-wow” sound. 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.
In essence, they give you the ‘wah sound’ you’d normally get from a wah-wah pedal, with one key difference: the sound is triggered by how hard you play (i.e. how hard you pluck your strings or your ‘picking attack’ and your playing dynamics) rather than having to rock your foot as you do on a normal wah.
As mentioned in the introduction, these units are mostly used in funk music for that signature “quack” or “bow-wow” sound.
Set it and Forget it
As discussed, they’re a set-it-and-forget-it option as opposed to a traditional wah pedal (which you need to control via the rocking switch with your foot). But there’s another less obvious benefit: using a wah pedal is sometimes incredibly impractical during a live performance, especially if you’re singing at the same time. Balancing on one leg while you wah with the other might not be the look you’re going for on stage.
Another massive benefit is speed. The circuits within envelope pedals react at a faster rate than we can physically move our feet, making a rapid wah sound possible. This effect is pervasive 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 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 they’ll ‘dumb down’ your sound – the range control makes them very responsive, so the harder you pick, the more wah you get.
Range (Sweep) Control
The range control adjusts the frequencies affected by the ‘sweep’ effect, meaning you have more of the effect when you’re playing high notes than when you’re playing low notes or vice versa. It can be convenient: you might not want wah on every single note you pick hard.
Sometimes just called ‘filter,’ this lets you choose between a low-pass, high-pass or band-pass. These different filters pick out different frequencies that each gives you a different vibe: a high-pass filter allows anything above a particular frequency get through, the low-pass lets anything below a specific rate through, and the band-pass put a band in the middle and anything either side of it gets through.
Closely related, 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 sound.
Attack/Response and Decay Controls
Some pedals include an attack control (some models call this response), which controls how quickly 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 that are too fast can also detract from the rhythm of your playing.
Buyer’s Guide – Key Considerations
StompBox Vs. Additional LFO
These pedals come in mainly two formats. First, there are the stompbox-style ones. These are small stompboxes that are easy to use and adjust. These will suit those who like to keep things simple. Then there are the ones with additional LFO (low-frequency oscillation). These are usually bigger, and suit those who want to experiment.
Where to Place it in Your Signal Chain?
There are two main ways to do it. A lot of guitarists choose to have them 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 them 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 into the pedal, producing some interesting sounds.
Product Round-up & Mini Reviews – Best Envelope Filter Pedal
Electro Harmonix Q-Tron
The Q-Tron is widely considered the best envelope filter pedal around, and capable of some of the phattest, funkiest sounds known to man!
The Q-Tron is a smooth envelope filter with a funky wah-wah tone and is modeled on the classic Mu-Tron III pedal used by none other than Prince, Jerry Garcia (listen to ‘Shakedown Street’), John Mayer (check out his track ‘I Don’t Trust Myself’), George Clinton (of Parliament / Funkadelic fame) and the legendary bassist Bootsy Collins.
The increased frequency response and improved signal-to-noise ratio make the Q-Tron perfect for use with any instrument, and its switchable Boost and Filter modes give you an unlimited amount of auto-wah effects.
Four filter modes (Low Pass, Band Pass, and High Pass filters and a Mix option), as well as sweep, range, peak, gain and boost dials give you plenty of options for fine-tweaking and adjusting
- Widely recognized as the best envelope filter around used by just about everyone, from Prince to George Clinton
- Modeled on the classic Mu-Tron III
- Holds to its funk and disco roots in aesthetics as well as tone
- No expression-pedal options
Electro-Harmonix Micro Q-Tron
If you like the sound of the Q-Tron but don’t have the budget, or want something a bit smaller for your pedalboard, the Micro Q-Tron is the one to look at.
Like its big brother, its an attack controlled sweep filter.
This simple pedal has the same 3 filter modes you find on the Q-Tron (Low Pass, Band Pass, and High Pass), minus the mix option.
Where it’s bigger brother gives you superior control, the Micro keeps it simple. The Q controls adjusts the dramaticness and intensity of the effect, and the drive knob controls the sensitivity of the pedal
- Funky wah sound modeled on the Mu-tron III
- Easy to use
- Pedalboard-friendly enclosure in a die-cast case
- Great price
- Doesn’t offer the control the Q-Tron does
EarthQuaker Devices Spatial Delivery V2
The Spatial Delivery V2 from Earthquaker delivers more experimental sounds than their Electro-Harmonix counterparts. Even the manufacturers themselves call it an ‘oddball’!
It’s great for funk of course, but the beauty of this pedal is it allows you to step outside the world of funk into unchartered music territory. You can conjure up some totally bizarre sounds which sound incredible.
You get three modes: Up Sweep, Down Sweep, and Sample and Hold with the other knobs (Range, Resonance and Filter controls) to help you emphasize the filter sweeps.
- Great for experimenting
- The sample and hold setting sounds incredible
- The price
- Possibly overkill if you just want something simple
Check out minute 1:30 for a great demonstration:
Source Audio SA127
The SA127 delights in playing with the 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 insane 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
- Many of the controls are merged. 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
- Since the controls are combined into just four dials, you’ll have to spend a little time learning how they all work together 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
The Pigtronix EP2 is a little more expensive than the others but comes with some extremely great features that set it apart. It has an LFO option for a start, so you can control your auto-wah sounds using either the envelope 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 them both together, for some very interesting sounds. It also has a staccato function which adds an extra response to the envelope. It’s well suited to playing funk.
- It has not just one, but two inputs for expression pedals that allow you to control speed and sweep direction separately, 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.
- 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 will do better to look at some of the other products on this list
- The complexity of the controls might take a while to get used to
- 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
The Maxon AF-9 takes a straightforward approach. 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
- A nice warm tone that closely resembles the legendary Jerry Garcia sound
- Lacks some of the extended functionality and fine-tuning controls of more advanced models
- It’s quite expensive for its simplicity
- No expression pedal input available, so it does lack the option for intimate control