Logic Pro X compressor

I usually write in Swedish, but this might interest some english speaking speakers so I make an exceptional exception.

Recently I watched some tutorials on mixing and mastering using the DAW software Logic Pro X (and the Ozone plug-in for mastering, but I’ll save that for another blog post). Even though I’ve used Logic since version 8, it turns out I haven’t used the compressor very good. In this post I explain what I learned from various tutorials about the built in Logic Pro X compressor.

vcaThe compressor has a number of modes in which it emulates different circuit types. The main classes of circuit types are:

VCA = Voltage Controlled Amplifier
FET = Field Effect Transistor (also a VCA but w/ different sound)
Opto = Optical compressor

Logic Pro X doesn’t actually name the circuit types after what it tries to emulate but (according to Mixing and Automation* by David Earl) the circuit types sounds close to:

  • Platinum – Logics own (default) compressor
  • Studio VCA – Resembles SSL G Bus
  • Studio FET – Resembles UA (UREI) 1176SE (silver front)
  • Vintage VCA – Resembles dbx 160
  • Vintage FET – Resembles UA 1176NE (black front)
  • Vintage Opto – Resembles Teletronix LA-2A

orderKnowing which compressors Logic is trying to mimic is really helpful because there are tons of manuals and tutorials for each one of the compressors named above.

In the compressor effect there are lots of presets to start from. But a preset is only to get you in the neighborhood. You should at least adjust the Compressor Threshold to fit your track after selecting a preset.

So where do the compressor go in the track? Well, at least put one in the beginning, before or after the first EQ. Then effects (reverb, delay etc). That is the basic setup, then you can tweak it in a million ways, but make sure to get the basics to sound good first.

Get that studio sound

To make the mix sound familiar to ”real” records, try to mimic the settings from the compressors in the list above:

SSL G Bus (Studio VCA)

ssl_g_busThis is a classic compressor from the 1970:s. SSL claims the G series has been used on more platinum records than all other compressors, combined. Some studio engineers used to call it the ”Good button”. It just makes everything sound good. Removes disturbing transients and makes the instruments clearer and crispier. Can be used for everything from organs, vocals to percussion and master bus. As you can see it has three settings for ratio, 2:1, 4:1 and 10:1. To mimic the SSL G Bus, set the Studio VCA to either ratio:

  • 2:1 – Mild compression
  • 4:1 – Intense
  • 10:1 – Limiter (brick wall)

But don’t set it to something in between, or else you will loose the G sound.

 1176SE (Studio FET)

ua1176seThis one is from 1968 and is perfect for rock, distorted instruments, percussion and intense vocals. For vocals, set it to ratio 4:1 and high attack/release and for percussion set it to higher ratio and low attack (adjust release to get the right ”ring” after the beat). Remember to set the ratio to either 4:1, 8:1, 12:1 or 20:1. If you set it to something in between you won’t get the 1176 sound.

dbx 160 (Vintage VCA)

dbx160I haven’t tried it but it is said to be rougher than the others and very aggressive. Can be used for kick, snare or other transient (percussive) tracks. Try it, you might like the sound.

1176LN (Vintage FET)

ua1176lnSimilar to 1176SE but somewhat different sound. Try it with base, electric piano, keyboard or drums. Maybe even vocals (compare with 1176SE). Note, the FET presets in the Logic Pro X compressor use this one.

Teletronix LA-2A (Vintage Opto)

teletronix_la2aThis is one of the first compressors ever made, from the early 1960:s. It is slower than the others and thus not good for percussive material. But it sounds fantastic for other tracks like base, keyboards, pads, vocals in the background etc. Set the ratio between 2:1 and 4:1.

Using the ratios from the pictures above you can mimic the sound of all these compressors using only the built in compressor in Logic Pro X, and it sounds great.

How to tweak settings

A work-flow to adjust the settings is to first select a circuit type and a ratio, then over-compress (pull the Compressor Threshold down really far, so the compressor destroys the sound). Then adjust Attack (how fast the compressor should begin to work when a high energy ”peak” arrives) and Release (how long it should continue to work after a peak). Turning up the Attack introduces a delay (in ms) before it begins and turning it down shortens the delay. The Release works similarly, but as the delay at the end of an energy peak. The last step is to slowly drag the Compressor Threshold up again and fine-tune it until you find the ultimate position. Also adjust the output Gain to get the volume right (doesn’t affect compression). You probably don’t need to touch the knee. As you can see from the pictures the ”real” compressors didn’t even have a knob for that.


In the first picture top right there is a Side Chain setting. From there you can make the compressor take its input from a Bus (instead of the current track).

You could for instance send the kick drum audio to Bus 1 (and turn off output for the Aux track created for Bus 1, change it from ”Stereo Out” to ”No Output”). Then at the track with the compressor (maybe a base, keyboard, distorted guitar or pad) set Side Chain to Bus 1. Now the track with the compressor on it will ”pump” in rhythm to the kick drum. The volume for the compressor track will go down when the kick hits and restore itself afterwards. Adjust the speed of the ducking with Attack/Release and adjust the amplitude of the volume cut with the ratio (and threshold).

Side-chaining can also be used if you have a voice-over track and some background music, and want to lower the volume of the background music when the voice speaks (ducking). To achieve this effect, send the voice track to a Bus (and set its output to No Output) and on the background music track, insert a compressor and set Side Chain on it to the Bus number. Now adjust the Ratio, Attack, Release and Threshold until you get that ducking going.


To really hear what you are doing with the compressor (and EQ etc) you should get a couple of studio headphones. I use the Audio Technica ATH M50. They are affordable but still sound great. If you live in Sweden you can find them on the low-price store net-on-net (otherwise, check out Thomann).

Good Luck!

As a bonus, here is me showing how to do side-chaining on guitars using kick drum as compressor input:

* I can really recommend the Mixing and Automation tutorial. It helped me a lot.


Om albertveli

Grävande programmerare.
Det här inlägget postades i Musik. Bokmärk permalänken.

2 kommentarer till Logic Pro X compressor

  1. Tritone skriver:

    This is so useful! Thanks a lot!

  2. Marcus skriver:

    Thank you for this.
    However, I propose that the correlations are slightly different, judging by the GUIs and controls:

    Studio VCA: Focusrite Red 3
    Studio FET: Universal Audio 1176
    Classic VCA: dbx 160
    Vintage VCA: SSL G Bus compressor
    Vintage FET: UREI 1176 silver
    Vintage Opto: Teletronix LA2A


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