Compressor pedals are important, and whether you know it or not, most (likely all) the guitarists you listen to use them!
In this article, we’ll take a look at some of the most important features to look for in a compressor. The different circuits, features, and controls you should look for! We’ve got a few quick recommendations as well if you’re in a hurry!
With that out of the way, let’s get started!
WHAT IS A COMPRESSOR PEDAL?
Compressor pedals (also called compressor/sustainer pedals) are used to keep an input signal in a specific range. This means they will attempt to “squash” signals that are too high and boost those that are too low.
Used at the beginning of a signal chain, compressor pedals ensure a consistent signal to everything following. This constant signal level helps to avoid any unwanted spikes or drops in volume. While compressors are generally used this way, some guitarists prefer to use a compressor pedal at the end of a signal chain. Used in this manner, they can keep the output volume of the guitar constant, without changing the sound or feel.
Another use for compressor pedals is as a boost pedal. With the output volume turned up higher than the input, compressors can provide a clean boost with or without adding compression. Keep in mind, that some compressors will color your sound, and so not all provide the same transparency as a boost pedal.
WHAT TO LOOK FOR IN A COMPRESSOR PEDAL
There are quite a few things to look for when pedal shopping. Here are some of the most important.
COMPRESSOR PEDAL CIRCUITRY
The type of pedal circuit influences both a compressor sound and feel.
Here are the most common types of circuits you’ll find in compressors:
- OTA or Operational Transconductance Amplifier circuits – This circuit is the most common type of circuit for a guitar compressor. Most compressors based on this type of circuit will color the natural guitar sound somewhat, which some like and others don’t.
- VCA or Voltage Control Amplifier circuits – These circuits offer fine control over the level of gain added to the sound and add little coloration to the sound. VCA compressors are often found in studio rack compressors.
- Optical compressor circuits – This circuit uses a light source and a photocell to control the compression. The light glows brighter or dimmer depending on how hard you hit the strings, and the photocell responds to the changes in light intensity. These are generally a bit less “snappy” than the other types of circuits and give a natural and smooth sounding compression.
- FET or Field Effect Transistor circuits – These are like VCA circuits in responsiveness and control, but also color the sound a bit more. Like the OTA circuits, though, some people prefered the colored sound, while some don’t.
- Tube compressors – Not exactly a separate type of circuit, tube compressors are often one of the above circuits with the tube added in the signal path to warm up the sound and give a more organic feel to the compressor.
- Parallel compressors circuits – These are like tube compressors in that they aren’t a separate type of circuit. This compressor type allows you to blend the compressed guitar signal back with the uncompressed signal. This can help to even out some of the “squished” attacks when compressors are turned up to increase sustain. By blending in some of the uncompressed signal, the initial attack is retained along with the increased sustain.
COMPRESSOR PEDAL CONTROLS
Aside from the circuit type, one other major thing to consider when buying a compressor are controls. While more knobs mean more control, fewer knobs mean the sounds dial in quicker.
BASIC COMPRESSOR CONTROLS
If you’re just looking for something to even out your clean sound and maybe add in some natural overdrive, a simple 2-knob solution may be all you need.
These provide a knob to change the amount of compression (labeled “Comp” or “Sustain”), and another to control the output level (labeled “Output” or “Level”). These are pretty straightforward to use and easy to dial in.
ADVANCED COMPRESSOR CONTROLS
If you’re looking for a compressor with lots of flexibility and you want (or need) a lot of control, look for these controls. Most boutique pedals offer some (or all) of the following fine-tuning capabilities:
- Blend controls – Like mentioned above, some compressors allow you to blend in a compressed and uncompressed signal to get a natural attack and lots of sustain.
- Boost controls – While just about every compression pedal lets you boost the output signal, some have a dedicated boost knob and a separate footswitch to give you two selecable output levels..
- Threshold controls – Some compressors offer an adjustable threshold, below which no compression effects take place. This can be useful in certain musical situations.
- Attack/Release fine tuning – Some advanced compressors let you control when the compression effect starts to compress the signal (“Attack”) and when it stops compressing (“Release”). Some compressors also allow you to control how quickly the compression effect takes hold (often called “Knee”). These changes can be subtle but can control how the compression interacts with other effects.
- Tone controls – Some compressors allow you to control the tone, either with switches (for Treble or Mid boosts) or knobs.
TRUE BYPASS VS. BUFFERED BYPASS
Many boutique pedals feature true bypass construction, but what does that mean? It’s worth taking a minute to explain the differences between a “standard” buffered bypass and true bypass.
True bypass means that the pedal’s on/off switch physically connects the input jack to the output jack. This should make the input signal and output signal essentially the same, but it does have one drawback. If you have long cable runs (or a lot of pedals) remember that each pedal and cable introduces a bit of resistance into the original signal. In this case, you may want a buffered bypass pedal to keep the signal clean and strong. Some true bypass pedals also have significant noise when turned on or off, due to the physical on/off switch. If you have a true-bypass reverb or delay, you also won’t get a natural decay of sound, since the effect will stop as soon as the circuit is disconnected.
Most standard pedals (like Boss) use a buffered bypass. While cheap pedals with poorly-designed buffers can degrade your tone, most buffered pedals have a negligible effect. Additionally, buffered pedals can help maintain signal level over long cable runs (or through true bypass pedals), and can have completely silent switching. For reverb and delay pedals, buffers also allow the reverb or delay “tails” to hold over after the pedal is switched off.
In the end, like most guitar effects, there is no one right answer. In fact, most guitarists use a mix of true bypass and buffered bypass pedals, depending on their specific needs.
COMPRESSOR PEDAL BUYER’S GUIDE
Here are some of the most popular compressor pedals you can find today! While these aren’t the only compressor pedals we recommend, these are great starting points!
A classic compressor that is easy to find, easy to use, and has features in compressors with double the price tag!
One of the oldest compressor pedal models still in production today. The MXR Dyna Comp uses an OTA circuit, true bypass, and is dead simple to adjust. The “Output” and “Sensitivity” controls are self-explanatory and easy to quickly dial in. Plus, the knobs are big enough to be adjusted by your foot while playing, in case you need to adjust on-the-fly.
One possible downside – the Dyna Comp is known for adding a bit of color to your sound, though. Since this pedal features prominently on the pedal boards of many legends, it’s safe to say that not everyone feels this is a negative!
Key Features: Sturdy construction, easy to use, true bypass, and easy to find!
Pros: Easy to dial in. Big, chunky knobs easy to adjust on the fly. True bypass.
Cons: Colors the sound a bit, which may (or may not) be what you want.
Rugged and reliable, the Boss CS-3 can help give your solos sustain for days!
Boss has been one of the staples of the guitar pedal industry for many years. While their pedals have both fans and detractors, they are the gateway pedals for many guitarists.
The CS-3 is the current compressor available from Boss and uses a VCA circuit. It features 4 knobs – “Tone”, “Sustain”, “Level”, and “Attack”. The “Tone”, “Level”, and “Sustain” knobs are self-explanatory, and the “Attack” knob adjusts how quickly the compression kicks in. This is useful for different playing styles or making the compression more (or less) obvious. The “Tone” knob allows the CS-3’s sound to be fine-tuned and can add a bit of warmth to the sound.
Boss pedals are buffered bypass, and so they may cause a slight change in tone, even when off, but the CS-3 is fairly transparent. Note that the compression effect on the CS-3 can be stronger when turned past 12 o’clock than other compressors. But if you’re looking to add some (almost) infinite sustain to a distorted solo, the CS-3 is a great, affordable option.
Boss has previously produced the CS-1 and CS-2 compressors. While these are slightly different in terms of features and circuitry, since they are out of production they have become harder to find and somewhat of a “collector’s item”. If you’re looking for an affordable workhorse, stick to the CS-3.
Key Features: Tone and Attack control, rugged construction.
Pros: Tone control to adjust the sound, Attack control for fine tuning compression effect.Can be very useful to add long-lasting sustain to any sound.
Cons: Not a subtle effect – can come on a bit strong and a bit more “squishy” than other compressors. Can take some time to dial in. Can change the tone a bit.
Transparent, versatile, but expensive, the Keeley can satisfy the most critical ears.
Featuring the same OTA circuit and true bypass, the 2- and 4-knob Keeley compressor let you pick the amount of tweaking you want to do! The price tag for the 2-knob is also slightly lower, but it does appear to be a little bit harder to find.
The 2-knob version features the expected “Sustain” and “Level” controls, while the 4-knob compressor adds “Attack” and “Clipping” controls. The “Clipping” knob is basically an input sensitivity control, so you can use this compressor for more than just guitar. The “Attack” knob lets you adjust how quickly the effect kicks in – useful for different playing styles.
Both models of the Keeley compressor are highly-regarded for being quiet (even when the output level is turned up) and for letting your tone pass unaltered. These two models, while pricey, are worth the cost if you’re serious about your rig!
Key Features: 4-knob version features Clipping control to use for other instruments, and an Attack knob for fine tuning. Both versions feature a transparent compression and true bypass.
Pros: Transparent sound. True bypass. Lots of versatility (especially the 4-knob version).
Cons: Expensive. 2-knob version not the easiest to find.
Compressors are an unsung hero of guitar effects, and you owe it to your own playing to try them out!
If you’re looking for something a bit different than the three options above, please check out our in-depth reviews of other compression pedals!
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