Mix Bus Compressor Topologies - which compressor to use on the master bus

Covering the various compressor topologies (designs) for the Mix Bus and how best to use them.

Compression


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Although Mastering is a specialised vocation requiring years of experience, great ears and solid technical grounding it is by no means unreachable to the bedroom producer. I have always been of the belief that anyone can make an attempt at mastering and that the experience alone will reap valuable rewards. My job is to help you achieve your goals and if mastering is your objective then that is what I will teach you.

However, before you can jump into a manic mastering project it would help tremendously if you knew what the mastering requirements are for your chosen genre and it is for this reason alone that I have created genre specific pre mastering video tutorials and written a book, Mixbus Strategies, on the subject of managing the master bus in your DAW because ultimately that is what we will be concentrating on – the mixbus.

Creating masters

Creating a transparent pre master is quite challenging because if you are anything like me you want to instantly hear a coloured (processes that alter the sound in harmonic ways) change to the mix. It is far easier to get emotional about a sound that is warm and fuzzy and has been teased with a lovely valve compressor than it is to hear that which is termed as ‘correct’ but has little colour. However, transparent pre masters are like hens’ teeth for mastering engineers as they are now in charge of colouring the mix and the fact that the pre master is transparent means they can apply any process without fear of compromising for the genre the pre master is intended for.

In this video I am trying to cover all eventualities from transparent to coloured mixbus processing and to achieve this a grounding in the different types of compressor topologies is required to help you on your way

Compressor Topologies (types)

VCA – Uses a Voltage Controlled Amplifier. VCAs are fast and have low distortion which makes them come across as ‘clean’. However, VCAs can sound aggressive if pushed. Because VCAs don’t add colour to a sound they can be used for transparent compression as they sound clean and smooth. Most common VCAs used are the SSL G Bus and the DBX 160.

FET – Uses Field Effect Transistors. FET compressors emulate the tube/valve sound using transistor circuits. They are fast and bright sounding and are popular with rock genres for exactly these reasons. FET compressors add both punch and colour to a sound and can be extremely useful on percussive sounds or sounds that need a snappy transients.The most famous FET compressor is the Urei 1176.

Opto (optical) – Uses a  photocell as a detector and a light bulb to determine the gain reduction. Different light sensor types and illumination sources affect the gain reduction in different ways. The time lag between the photo cell and detector makes for a slow attack and release and this makes this type of compressor perfect for processing vocals, performing gentle automatic gain changes and mastering. The most famous opto compressors are the LA-2A and Avalaon AD2044.

Vari-Mu – Uses a valve (tube) as the variable gain reduction. They are slow to react which makes them perfect for ‘gluing’ purposes and the ratio increases with gain reduction which gives this topology such a distinct sound. This type of compressor works best on the master/group bus as it glues sounds together into a single homogeneous sound. It can be used to add warmth and thickness to a sound. The most famous Vari-Mu compressor is the Fairchild 670.

Now that we understand how to run a parallel channel/copy in the DAW and have familiarised ourselves with the various compressor topologies we can process a Hip Hop drum beat confidently.

In the video I use all the main compressor topologies and explain how each one works and why they can be used on the mixbus. I  explain each and every compressor type/topolgy in detail and share with you my personal favourite plugins to use at the master bus/mixbus.

Plugins used in this video are:

Softube FET Compressor

Softube CL1B Compressor

Slate FG-Grey Compressor

Slate FG-Red compressor

FG-MU Compressor

FabFilter Pro C compressor

Softube TLA-100A Tube Leveling Amp

Topics covered in this video are:

  • Understanding the Mix Bus (Master Bus)
  • Various Mix Bus Compression Techniques
  • Linear Phase versus Minimum Phase
  • Saturation and Valve/Tube
  • Sheen and Grit
  • Gluing
  • Leveling Amps
  • Smoothing Transients