Using classic compressors in your mixes
By Rob Stewart - JustMastering.com - Last updated August 7, 2017
Classic hardware compressors are widely available these days, and even though the original vintage models are getting more scarce, hardware re-issues are easy to find, and software emulations are available from various sources. These vintage dynamics processors can be helpful at times not only because of the character they can impart on your mix, but because their interfaces are relatively simple, sometimes only presenting one or two controls to dial in the compression you are looking for. These pieces of vintage gear are not created equal though, and some are better suited to one purpose than another.
Rather than delving into the merits of the software vs hardware versions or whether you should buy original or re-issue gear, I will discuss the functional differences between several classic processors so that you can make an educated choice when deciding to either buy, or use one for your mix. Please note that my suggestions are not intended to be absolute - your mileage may vary. As with any piece of gear, particularly expensive ones, I recommend trying before buying if you can, to make sure it will do what you need it to.
The API 2500 is a highly configurable compressor/limiter that features fully adjustable attack (30 microseconds to 30 milliseconds), release (50 to 2000 milliseconds and automatic “variable” feature), and ratios of 1.5:1 through to infinite. There are several other features as well, but these along make it effective as a compressor or limiter, on a wide range of sources.
Use the API 2500 as either a bus compressor/limiter, or on any instrument where you want to control the dynamics of the transient, attack portion and well into the release/sustain portion of the instrument.
DBX 160 Series of compressors (160, 160A, 160X, 160 XT)
The DBX 160 series of compressors are well known for sounding extremely natural. They offer true RMS level detection, and newer models offer a choice between hard and soft-knee features. Compression ratios range from none (1:1) to infinite.
The attack (5 to 15ms) and release (8 to 400ms) times are both program dependent, so to set the compressor for the source, you first choose the mode (hard or soft-knee), the ratio and threshold, and the compressor does the rest based on the dynamics of the material itself. The original 160 is well known for being very good on bass, and on electronic drums, to help bring out more punchiness. At 5ms, this family of compressors is not fast enough to act on sharp transients, but, you can certainly use it to control most of the attack portion of the program material. The sustain portion can be controlled to an extent as well, though at 400ms, not as much as you could with the API 2500.
Fairchild 660 (mono) and 670 (stereo) Limiters
Known for being an exceptionally clean sounding limiter, the Fairchild 660 and 670 limiters feature a super-fast attack time between 0.2 and 0.4 milliseconds, with a release time of 0.3 to 25 seconds (yes, that’s 25 seconds!), along with an automatic release setting option. The compression ratios available are anywhere from 2:1 to 30:1 which allows you to select a relatively gentle compression ratio if desired.
As with the 1176 and the LA-2A, the Fairchild 660 and 670 are designed to work on the transient, and attack portions of the program material, once again, this makes them well suited to shaping the dynamics of drums, rock vocals, or anything where you have inconsistent attack notes. The super long release time allows you to create a very smooth release, but it is important to note that all the control is driven by transients or early attack.
SSL G Series Bus Compressor
The SSL G Series Bus Compressor features a relatively simple interface, with fixed controls, but it is widely known for helping “glue” mixes together. It offers three ratios - 2:1, 4:1 or 10:1, with fixed attack times between 0.1ms and 30ms, and fixed release times between 0.1ms and 1.2 seconds, with an “Auto” release setting as well.
Even though the settings are not continuously variable, you have a relatively wide range of options. It is an obvious choice on a mix bus, either on a whole mix or on sub mixes such as the drums. You can use this compressor to control transients, attack and sustain.
Teletronix LA-2A Levelling Amplifier
With its fixed attack time of 10 milliseconds, and an automatic release time, this classic dynamics processor is highly effective on rock vocals or bass guitar, and any other situation where you want to adjust and control the attack portion of the instrument. It offers “Compress” (low ratio) and “Limit” (higher ratio) modes at the flip of a simple switch.
The LA-2A is an effective, efficient and easy-to-use design that allows you to create musical results relatively quickly. For example, you don’t have to think too much about compression ratios or or attack and release times. You can let your ears be your guide, instead. At 10 milliseconds, the LA-2A can control the attack portion of the program material but it is too slow for sharp transients. This is why it is well suited to limiting vocals or bass which typically have slower attack portions than other instruments such as drums or acoustic guitar.
Urei/Universal Audio LA-3A Audio Leveler
Much like the LA-2A, the 3A features a very simple set of controls, allowing you to dial in your sound by ear, relatively quickly. It features a much faster attack time of 1.5ms, and automatic release.
The LA-3A is well suited to Drums, Rock vocals and Guitars, in situations where you want to control the attack portion of the material, and a large portion of the transients as well.
Urei 1176/Universal Audio 1176 (and family) Limiting Amplifier
The Urei 1176, and Universal Audio 1176 family was groundbreaking technology in its day, with a super-fast attack time, it is a fantastic limiter. It features 4 selectable ratios, and a release time of between 50 and 1100 milliseconds.
The 1176 is effective on almost anything. Similar to the LA-2A, it is best used in situations where you want to work on the attack portion of the instrument, hence, it is most useful on drums, rock vocals, electric guitars, or anything where the attack portions are too “loose” and need tightening up to make them of more consistent volume.
There is a famous “All four ratio buttons in” trick with the 1176 that many users love. This was an accidental feature of the hardware, and has been emulated in some of the virtual/software versions that are out there. Your mileage may vary, but it is always worth a try. With long release times as over 1 second being possible, the 1176 offers some interesting dynamics shaping options.
Tube-Tech CL 1B
Known for exceptionally smooth compression, particularly useful on vocals, the Tube-Tech CL 1B features ratios from 2:1 to 10:1. What sets the CL 1B apart from all of the other compressor/limiters listed above, is its attack setting options. The CL 1B allows for an attack time of between 0.5 and 300 milliseconds (just under 1/3 of a second), making it not only capable of fast compression/near limiting, but it is also capable of being the “slowest” compressor on this list!
Why would you want a slow compressor? Well, the best use of a slow compressor is when you wan to focus on, and control, the sustain part of the program material, while leaving the attack portion largely untouched. A great example is acoustic guitar, where allowing the attack portion to pass through to a certain extent, and compressing the sustain portion, you can increase the perceived sustain of the instrument without making it sound “smashed”.
The CL 1B is a great choice if you want relatively transparent sounding compression on acoustic guitars, or vocals, but it can also be used on mixes, and drums if you choose faster settings.