Guitar 101: What Is a Compressor Pedal? Learn How to Use a Compressor Pedal

A compressor pedal is a stompbox pedal that sits in your signal chain and levels the dynamics of your guitar performance. When you play something very quietly, a compressor can boost the output to make it more audible. When you strike a string too forcefully, the compressor will dull the sound of your pick attack for a smoother overall sound.

By harnessing the dynamic range of an audio signal, compression pedals can do many things for a guitarist:

• Boost clean tone. If you want a clean guitar sound but are getting buried in your band’s mix, a compressor can amplify your original signal and make you more audible. Of course, you can also adjust your overall volume on your amplifier, but many players appreciate the subtle effects that pedal compressors bring to their guitar tone.
• Provide funk and chicken-pickin' tones. A guitar is a treble-focused instrument. So when you boost the guitar’s audio signal, you’re boosting that high-end sound. This is ideal for funk lines (think the guitar solo on Michael Jackson’s “Billie Jean”) or country-western leads.
• Add sustain to lead guitar. In addition to compressing your input signal, many compressors can add sustain to their output signal. Certain compression-focused guitar pedals feature knobs to adjust sustain (also called “release”). The Boss CS-3 Compression Sustainer is known for this, as is the Keeley C4 Compressor.

Most guitarists place a compressor early among their guitar pedals. The idea is to compress the clean guitar tone before sending it through an overdrive pedal, phaser, or delay. If you place the compressor after those other guitar effects, you will end up compressing the sound of those effects. This can significantly change the character of those effects pedals, particularly overdrives and delays, and can have unintended effects on your overall output level.

Compressor pedals typically have one to four knobs to control their functions (and some have even more). Here are some of the more common dials you might find on a compressor effect pedal:

• Attack. This controls what the compressor does to your input signal. If you want to hear the hard pluck of your pick strokes, turn the Attack knob up.
• Sustain or Release. This controls the release times of your notes. Not all compressors control sustain, as their true function is actually to suppress loud notes so that quiet notes sound comparatively louder.
• Compression or Depth. This simply dials in the overall amount of compression provided by the pedal. If you set this parameter low, you will get a “transparent” sound that creates only subtle alterations when you turn the pedal on. (Note: If your pedal does not contain individual “Attack” and “Sustain” knobs, then this knob will be essentially synonymous with the “Attack” parameter.)
• Level. This is the overall volume control for your pedal. If you mainly want to use your compressor as a boost, turn the Compression knob down and the Level knob up.
• True Bypass. If your pedal is labeled True Bypass, this means it does not contain a buffer to boost your overall sound. It also means that the pedal will allow an audio signal to pass through at all times—even if it isn’t connected to a power supply.

Many manufacturers make excellent compressor pedals, and it’s hard to go wrong. Here are a few of the most popular among today’s guitar players:

• Boss CS-3. As is often the case, Boss has built what many consider an industry standard, later tweaked by other manufacturers. The compressed signal of a Boss pedal defines many funk guitar performances.
• MXR Dyna Comp. Heard on countless classic rock recordings and perhaps most famously associated with The Police’s Andy Summers.
• Keeley Compressor. A boutique pedal inspired by earlier Boss models. Keely offers versions of the pedal with two knobs and four knobs, but both produce the same range of sounds. (The two knob model contains more options inside the casing.)
• Wampler Ego Compressor. Another boutique pedal. Known for its Tone control, which is rarely found on compressors.
• Xotic SP Compressor. A two-knob compressor with a compact footprint that makes it easy to fit on packed pedal boards.

There are countless other compressors from brands like Electro-Harmonix, TC Electronic, Strymon, Rothwell, Way Huge, Empress, and more. As with most musical topics, a choice of compressor comes down to personal taste. In fact, some players forego compression altogether, preferring to let their dynamics come straight from their tube amp.

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