A Compressor pedal can be something of a mystery to players both new and experienced in the world of guitar effects and audio processing. What does it do? Where should it go in my chain? What’s the difference between them? We’ve got answers for you in this comprehensive guide so you can feel confident in making the right Compressor Pedal selection for your style, tone, and pedal board.
What is the role of a compressor?
Originally invented by the producers of early vinyl records, compression, at its most basic, was used to prevent unwanted volume peaks because the needle would fall out of the groove if the record got too loud. Now the compressor is a tool used on nearly every professional recording you’ve ever heard, having multiple functions depending on the instrument it is applied to and the sound an engineer wants to achieve. For guitar players, compressor pedals build unique tone, affect dynamic range, and can act as a signal boost to let the guitar stand out during a solo or live mix.
Dynamic range, or simply the loud and softness of a guitars volume, is generally “flattened out” by a compressor, creating an even volume. They can also add sustain, which lets the note ring out longer as seen by players like David Gilmour of Pink Floyd. Be careful not to overdue it or the guitar can sound squashed and unnatural, unless that’s what you’re going for!
Many guitarists also click on their compressors when they want their guitar to brighten up and stand out amidst a solo or particularly funky rhythm. Like a volume pedal, a compressor can give you added thump or sheen, without adding distortion or fuzz. You can achieve this by turning down the “compression” knob and turning up the volume or gain knob. Also, to have it be less noticeable, keep the compressor toward the front of your chain (before distortions and fuzz). On the other hand, you could put it at the end of your chain when recording, so that it sounds more like you’re playing in a studio.
Beyond dynamics, compressors can have a particular effect on overall tone that many guitarists find desirable. Certain staples like the MXR Dyna Comp or Keeley 4 Knob have a specific tonal magic that can add that extra warmth and grit that your rig has been asking for, and even enhance other effects in your chain. Experimentation is key and sitting down with multiple brands and models will help you in the quest for your sound.
How Is Compression Used?
The knobs of a compressor are generally called threshold, ratio, attack, release, and gain. Threshold can be thought of as your “volume ceiling,” it is the amount of input volume it takes for the compressor to take effect. Ratio is like poking holes in that ceiling, allowing some volume to get through so your signal does not sound too squished (2:1 to 4:1 are generally good for electric guitar and bass). Attack is how long it takes (in milliseconds) the compressor to compress the signal once it hits the threshold and release is how long it takes to end the compression. For clear, uncolored sound, leave your attack at less than 1ms and your release at 40ms. Lastly, the gain knob is meant to bring your signal back to a good level so that it sits properly in the mix. In a studio setting, compression is meant to be transparent and not color a signal’s tone. On vocals especially, an engineer does not want the voice to sound squashed or unnatural, rather they want to ensure the levels are not peaking during a particularly soulful vocal performance.
During a live performance, having a compressor on your master track helps stop unwanted volume peaks that can cause distortion, feedback or even blow your speakers. In this sense, the compressor acts as a limiter, as long as you set the ratio to 20:1 or higher. This ensures that if a singer starts screaming into the mic, you’re not going to damage your speakers or the ears of your audience. Like a signal boost, it also helps instruments to pop out more during a live performance.
For guitarists, a compressor pedal can add articulation to individual notes, say during a fast arpeggio or tapping run. For example, if you’re doing your best John Petrucci impression and sweep picking a tasty A minor arpeggio, unless you pick each note with the exact same velocity, the tone and amplitude will not be even. A compressor will normalize the notes, regardless of tube or solid-state amp. On acoustic guitar, some mild compression will help the notes ring out evenly and add a nice thickness, while taming high-end squawk. The tone knob on a compressor is usually there to compensate for the loss of high or low frequencies, which can sometimes be sucked out with a compressor.
Some guitarists avoid compressors for genres like blues or reggae because having control of dynamics is essential to their playing. While obviously not every blues player avoids compressors, they like to retain the expressive use of volume and string attack, which compressor pedals can sometimes suck out, it comes down to your individual technique and what kind of sound you want from your guitar.
Compressor Pedal Options
A killer compressor, Wampler’s Ego gives you a ton of control over how you want its compression to sound. The blend knob allows you to control how much the pedal is affecting your guitars signal, think of it as a “wet/dry” knob, allowing you to dial in just the right amount for your tone. Sustain is your amount of compression and attack brings in more snap from your strings. Tone is great for giving you a top end boost that might get sucked out when the compressor is turned up. The volume control should be obvious but also remember that you can crank up the volume, keep the sustain and blend pretty low, and then you have a sweet, sparkly clean boost.
The Ego has a rich, organic sound, is superbly quiet, and offers completely true bypass, so as not to drain any tone if disengaged. Having 5 knobs really gives it an edge because it lets you acutely dial in that “barely there” sound for subtle dynamic control. While particularly smooth for clean and overdriven tone, this pedal will definitely please players from all genres, guitar or bass. Hand-built in the USA, Wampler also offers a Mini Ego, which saves space but changes the attack and tone knobs to switches.
Wampler Ego Mini
Known for their miniature, uniquely shaped pedals, the Hotone KOMP gives a smooth, bright compressor in a stompbox about the size of two 9 volt batteries. This tiny pedal can squeeze into your chain and push through a big sound. It’s got 3 basic controls, a big compression knob on top with 2 LEDs inside, volume, and tone knobs. It also has a small button called “spark” which gives the signal a cheerful high-end boost.The pedal uses optical compression, meaning a photocell and a small light control the way the pedal compresses its incoming signal. This method is modeled after the Urei LA-2A, one of the most famous compressors of all time. It’s a desirable effect because of the way the attack and release work with the bending of light, creating a soft, musical character unlike typical compressors. While it may suck some bottom out of bassier, fuzzier tones, you can keep the main compression knob at around 2 or 3 to make the pedal as transparent as possible.
The KOMP is a great space saver, but don’t underestimate it because of its size. Its tone is clean, lush and great for beefing up clean chords and plucky leads.
MXR-M102 Dyna Comp
A favorite of Nashville-style country and Americana guitarists, the M102 has been heard on thousands of recordings, making it a true classic. With only two big knobs, volume and sensitivity, the box brings great tone with remarkable ease. The sensitivity knob controls the ratio, meaning 2:1 is light compression where 20:1 is heavy compression
Certainly beloved by chicken-pickin’ guitarists for that shiny pop it gives your strings, the simplicity of the pedal makes it a good entry point for beginners that will end with being a real workhouse on your chain. It’s powered with either a 9-volt battery or AC adapter, and is true bypass so it won’t color your signal when disengaged.
Keeley 4 Knob Compressor
The 4 Knob is a rich and flexible pedal, as Keeley is renowned for their build quality and high-end materials. Its 4 knobs – sustain, level, attack, and clipping – give this pedal an edge over its competitors. Sustain controls the amount of squeeze on your guitar, allowing for smooth, even note velocity, while attack is how long until the compressor turns on (you can dial this down so the effect is subtler on the front end of your note). Clipping provides control for the input sensitivity, so depending on if you have high or low output pickups, you can adjust the knob accordingly. It also can add a bit of drive and power to low output signals, giving the tone an added bite.
Known for being extremely quiet, this compressor is an all around fantastic sounding pedal that’s good for clean, dirty, and even heavy metal styles.
TC Electronic HyperGravity Compressor with Tone Print
An exceptionally versatile stompbox, the HyperGravity offers three different styles of compression – spectra, vintage, and tone print. It’s also got the parameters we’ve come to understand – sustain, level, attack, and blend. The beauty in this piece is how it captures the sounds of compressors across time. The vintage setting is reminiscent of the MXR Dyna Comp (that classic warm tone that many modern compressors are emulating) and the spectra setting, which emulates TC Electronic’s system 6000 music software (used in pro studios around the world). Then you have tone print, which can actually change the parameters controlled by the knobs by connecting the pedal to your computer or smart phone. From there you can dial in multiband compression, which is a way of cutting or boosting certain frequencies that may be lost in the actual compression. This gives you an insane amount of control on the shape of your sound and the EQ response of your instrument. While this may be confusing to beginners, there are plenty of presets to help you learn what you’re doing with the pedal.
Another nice feature is that you can switch between true bypass and buffered bypass. Buffered bypass, which many guitarists prefer to true bypass, is something that prevents tone suck over a long signal chain (more than 16.5 feet) and can help maintain a consistent, lossless tone.