What is an Effects Unit? – Get Funky!

What will sound be without some funky effects? Pretty mundane I would assume. A big part of professional audio productions is the effective application of various audio effects. As an aspiring sound engineer or producer, you will eventually need to know about the different effects available. Hence, today we will be asking – What is an Effects Unit?

When it comes to effects in audio, there are many different types of them, packaged into various hardware units that are made available in the market. So, for this article we will start by addressing the core function of an effects unit, and how it is generally used to benefit various audio productions. Okay, without wasting any more time, let us start learning!

Introduction – Cool Sounds!

Also simply referred to as “pedal”, an effects unit is an electronic device used to modify sounds from musical instruments or other audio sources. Effects can either “color” a sound or drastically transform it. Effects units are also used by musicians during live shows or in the studio, typically with electric guitar, electronic keyboard, electric piano or electric bass.

Rack Effects

Rack effects units / Photo by AKX_ from Finland / CC BY 2.0

Although effects units are very often used with electric or electronic instruments, sound engineers can also use them with acoustic instruments such as drums and vocals. Some examples of commonly used effects units include wah-wah pedals, delay units and reverb units.

At the moment, there is no concrete system to categorize different effects. However, the following are the seven typical classifications in the audio industry: distortion/overdrive, dynamics (altering loudness), filter, modulation, pitch/frequency, time-based and feedback/sustain.

Various Form Factors

You can find effects units in the market, available in various form factors. The smallest, more affordable, and most rugged ones are “Stompboxes”. In general, the more expensive ones are the “Rackmount” units that offer a wider range of functions. An effects unit can either have analog or digital circuitry, or a hybrid of both.


This is the type of effects unit that musicians often use. Stompboxes are designed to be placed on the floor and can be put on a pedalboard (that houses effects units) to be operated by the user’s feet. The most basic stompboxes include a single footswitch, one to three potentiometers (knobs) for attenuation of the effect, and a single LED that indicates if the effect is on.


Stompboxes forming an effects chain / Photo by Claudio Matsuoka / CC BY 2.0

Stompboxes with a more complex or advanced design may include multiple footswitches, many knobs, additional switches, and an alphanumeric LED display (typically used to indicate the status of various effect parameters with short acronyms such as DIST for “distortion”). These units are commonly known as multi-effects units.

Connecting two or more stompboxes creates an “effects chain”. These are usually placed between the guitar and the amp or between the pre-amp and the power amp. If a pedal is not used or “inactive”, the electric audio signal that goes into the input of the pedal diverts onto a bypass circuit, resulting in an unaltered “dry” signal that is routed into other effects in the chain.


Built with a durable metal chassis, rackmounted units are typically designed with “ears” which allows them to be screwed into a 19-inch rack (the standard in professional audio). They are typically mounted in a rugged plastic case (road case) with front and rear covers that protects the controls during transportation and can be removed during a live show setup.

Rackmount effects

Rackmounted units with foot controllers (left side) / Photo by Johann / CC BY 2.0

A rackmount unit may have a similar electronic design as a stompbox unit. But a rackmount’s circuits are usually more complex. Rackmounts typically have several different types of effects. They are very often utilised in recording studios and by live sound engineers during live shows. Professional musicians may also use them in place of stompboxes.

Rackmounts have knobs and switches on the front panel for effects attenuation, and are usually compatible with MIDI digital control interfaces. Rackmounted effects can be remotely operated by musicians using a “foot controller”. There are also “Shock-mount” racks available, that are designed for users who frequently move gear between venues.

Built-in Units 

There are amplifiers and even electronic instruments in the market, that have effects units integrated into them. For example, electric guitar amplifiers may be designed with built-in reverb and distortion effects, while acoustic guitar and keyboard amplifiers can have a built-in reverb unit. For instance, the Fender Bandmaster Reverb amp, had built-in reverb and vibrato.

Digital Modeling

Guitar amp with digital modeling and built-in effects / Photo by Scott Cranfill / CC BY 2.0

Today, you can easily find guitar amplifiers with built-in multi-effects units or digital modelling effects. However, it is less likely for bass amps to have built-in effects, although some models may include a compressor/limiter or fuzz bass effect. Other instruments with built-in effects include Hammond organs, electronic organs, electronic pianos and digital synthesizers. 

Multi-effects and Tabletop Units

Also known as “multi-FX”, a multi-effects unit can be a single effects pedal or rackmount unit that provides a variety of electronic effects. Multi-FX units allow users to save a set of adjusted parameters as “patches”, allowing musicians quick on-stage access to different effects chains. Multi-effects units offer a range of distortion, chorus, flanger, phaser and reverb effects.

Multi-effects pedal

Multi-effects pedal / Photo by Nedko at English Wikipedia / CC BY-SA 3.0

Some of the more high-end, expensive multi-effects units may also include looper functions. A tabletop unit is a multi-effects device designed to be placed on a desk and operated manually. An example is the POD guitar amplifier modeller by LINE 6. DJs also use a special type of tabletop unit, that can be placed next to mixers, turntables and CD scratching gear.

We have come to the end of this article. Hopefully with this information, you guys will now be more comfortable using various effects units. Stay tuned for more articles about audio effects!

Do leave comments or questions below, and share this article with your music loving friends!



When I'm not rocking out to great music, I'd prefer to be sleeping on a field on a windy day =)


  1. Hi Farhan,

    What an informative article! I could actually refer someone like my father to your article and he would be able to come away with a basic understanding of sound effects.

    I’m an amateur guitar player and I’ve had some “cheap effects” in the past. I’ve always wondered about the various form factors besides the standard stomp box. I have a better understanding now.

    You did a great job enumerating the basic points of effects units.


    • Hey Britt!

      Yeah, sound effects have many uses. From practical ones such as adding reverb on a dry vocal track, to purely creative uses such as adding a “wah” effect to a guitar tone to make it more funky!

      Thanks for reading!

  2. Hello Farhan,
    I didn´t know that there are so many different effect units, I always thought the only ones are those being used for adding an effect to an electric guitar – I mean those stompboxes… Do you know if there are also effect units available for a simple keyboard? I want to buy a keyboard for practicing music and I often find the Instruments which are available in a keyboard too boring.
    Thank you for this post…

    • Hello Fabi!

      Electronic keyboards are very versatile and some higher end models have many synthesized sound samples and effects modules that are built-in. Check out popular brands like KORG and also NORD. These two companies offer a wide range of synthesizers / keyboards.

      Thanks for reading!

  3. The great thing about electronics is how much you can improve on things. I remember many musicians using the floor pedals for different effects for some of their songs. Later on, you got to see the multi-units as you mentioned instead of mounting multiple foot pedals to a board.

    It stands to reason; they would have the rack mount units as well which they never had available that I had seen anyone use in the past.

    Excellent article to explain all the variations and combinations for effects unit.

    • Hey Travis!

      Thanks for dropping by my site. I’m glad that you have found this article to be educational.


  4. Without effects units, some of the greatest songs of all time may not have ever been created! We can attest the sound of Prince, Michael Jackson, Bono, Rick James, Jimi Hendrix, Stevie Ray Vaughn and so may others to the use of effects.

    Do you have a particular set of stomp boxes or effects pedals that you fancy over another? What brands are your favorite?

    • Hi Christian!

      Yes, for decades, many musicians have been using all kinds of effects creatively when producing music. Looks like you are already well aware of this fact yourself. I generally use multi-effects units from BOSS, due to their superb sound quality and highly durable construction. I also occasionally use digital modelling amps by Line 6 as well, due to their convenient digital features.

      Thanks for reading!

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