Learn about the different types of audio compressors in music. If you are new to compression, start by reading our guide to getting started with compression.
Compression can be a little tricky to get your head around.
The principle is simple enough; make the loud parts quieter and the quiet parts louder. You end up with a compressed and more balanced sounding audio file, that sits better in the mix and doesn’t prick your ears when the transients hit. It takes everyone some time to really be able to hear what a compressor is doing and understand how it’s working its magic.
With so many options for compressors, from third-party plugins and DAWs coming standard with multiple compressor plugins, it can be a struggle to learn the differences between compressors and find your favourite(s).
More confusion can arise when your favourite producers and engineers say ‘X’ is my favourite compressor because… ‘I like the sound of it’.
But what is this ‘sound’ they are referring too?
What happens when you get sent the recordings of a full orchestra?
Is that compressor that you use on your vocals, drums, pads, and everything else going to do those expensive recordings justice? What is the difference between Optical and FET?
Why would you use one and not the other? If you want to be at the top of your compression game, you have to understand that different types of compressors and techniques serve different purposes. By the end of this article you’ll know about the different types of compressors and their uses.
Gaining confidence through knowledge is the way to make informed decisions that can take your music to the next level.
VCA (Voltage controlled amplifier)
Classically quite a transparent compressor type, VCA compressors are clean sounding and don’t colour the sound with characteristics. Usually they have a high sensitivity with attack and release times, making them ideal for audio with lots of spiking transients like drums for example.
FET (Field Effect Transistor)
If you’re looking for a great all round compressor FET’s are brilliant. They do provide a lot more colour and character than a VCA compressor does. They are known to sound quite aggressive, due to the distortion they impart on the signal. They also have very quick attack and release times and are my compressor of choice for slightly crunchy drums.
The 1176 by Urei (Universal Audio) is by far the most widely known FET compressor, if you’ve spent time in professional recording studios you will know the 1176.
Waves also offer a digital version of it in the CLA-76. FET compressors sound great on almost everything.
Valve/Tube (a.k.a Vari-Mu)
These compressors are generally far from transparent sounding too; they usually provide some colour and distortion on a signal. In comparison to FET and VCA they usually have slower attack and release times so aren’t as ideal for taming quick transients in drum tracks for example. Something they are great for is smoothing out overall dynamics and gluing parts together. Making them an ideal candidate for bus compression and mastering.
These types of compressors are sometimes referred to as levelling amplifiers. Audio input signals provide electricity for the compressor, which is then converted into light, the intensity of that light is read by a sensor that determines the amount of gain reduction.
The louder the signal is, the brighter the light shines, and the brighter the light shines the bigger the gain reduction. This process results in a slower attack time and smooth release, meaning they’re much less sensitive to peaks and transients. The smooth compression Optical compressors make them a popular choice for vocals and bass.
Universal Audio’s LA-2A and LA-3A are widely known Optical compressors, Waves has digital versions of both of these.
Having one go to compressor is all well and good for speeding up your workflow. Hopefully at this point you can understand how different compressors would behave differently to one audio signal. Understanding the differences between compressors allows you to make better decisions when mixing.
Try out some compression with the knowledge learnt in mind and see if you can hear a difference!