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How to optimally use a LA-2A compressor

Écrit par MixCorner le 25 novembre 2019, dans - Audio - Matériel - Tutoriel. | 142 visites pour cet article.

Originally made in the early 60th, the LA-2A has been - and still is – extensively used in recording studios. The numerous plugins developed allow to use them in your DAW with –sometimes– very realistic emulations of this legendary compressor.

BUT… WHERE IS THE “THRESHOLD” LOCATED ?

Generally speaking, the Threshold is set up to the signal entry level allowing a properly work of the compressor. If no signal enters in the compressor , the latter will simply not work.

Let’s see how it works on a “classic” compressor :

Compresseur fourni avec Pro Tools / Pro Tools stock plugin
Compresseur fourni avec Pro Tools / Pro Tools stock plugin

In the compressor showed above, the Threshold - represented by the white line (1)- is set to the audio signal level (red arrow). As long as the signal remains below this level, no compression is applied.

The « working philosophy » of the LA-2A is radically different from the one mentioned above. In practice, instead of “lowering” the Threshold level to the entering audio signal.. the signal will be increased to the Threshold’s level which is fixed in the LA-2A.

LET’S HAVE A QUICK LOOK AT THE LA-2A FRONT PANEL

Universal Audio Teletronix LA-2A Silver Model
Universal Audio Teletronix LA-2A Silver Model

  • 2 main settings : Gain and Peak Reduction.
  • 2 secondary settings : Switch Comp/Limit and Emphasis
  • A « VU meter » displaying the amount of dB subtracted of the entering signal (generally called Gain Reduction or GR)
  • And, of course a power switch On/Off

As you may notice, in this case the user has only 2 main settings to work while in the other classic types of compressor you may have 5-6 settings that can be inter-associated, which, at the end makes this LA-2A compressor easier to work with.

OK, BUT HOW SHOULD WE PROCEED TO USE IT OPTIMALLY ?

1st step :

The first control that will be concerned is the Peak Reduction one. This might look strange for new users but that’s the way to do. In practice, tweaking the Peak Reduction Pot will increase the incoming audio signal level as previously mentioned.

As the Peak Reduction Pot is tweaked to higher values, the peak reduction is also increased.
The Peak Reduction’s ideal amplitude is not dependent of standard physically determined audio parameters but depends of the music style, the type of mix you’re doing and user taste..but this is not part of this review !

2nd step :

Once the Peak Reduction level selected is applied, the audio level of the compressed signal will be lowered. That’s at that stage that the Gain Pot will act and compensate the audio level lost during compression.
The objective (as for any type of compression) is to keep the audio signal level similar when the compressor is “ON” or not.

This allows for an A/B objective comparison with or without compression. As you may certainly know, human ears usually perceive higher audio levels as sounding better.
This reminds you the importance of signal levelling step.

Once those principles known and applied, the user already understands 90% of the LA-2A capabilities.

COMP vs LIMIT MODE


That peculiar setting allows to modify the ratio between approximately 3:1 in “Compress” mode to Infinite:1 in “Limit” mode.
It should be mentioned that the reality is a little bit subtler and that the Ratio is NOT strictly fixed but depends of the nature of the signal source entering into the compressor and its level.

The user may certainly experiment but from previous experienced users, it’s generally acknowledged that the differences may be very subtle.

EMPHASIS


This « pot » is dedicated to modify the compressor’s behaviour according to wavelength frequencies.
Turned towards the left leads the compressor to react more lightly on bass frequencies and deals more with the higher ones.

OTHERS COMPRESSORS WORKING UNDER THE SAME PRINCIPLES

Over the years, the original model LA-2 has been declined in many versions. Here are some of them.

Universal Audio LA-2
Universal Audio LA-2

The LA-2 is the original one and has been designed in the early Sixties. It’s the winner for sweet compression and shines on vocals. It’s also the most expensive one and the hardware version is not only very rare to find but also very expensive…

Universal Audio LA-2A Gray
Universal Audio LA-2A Gray

Build in the Mid Sixties, the Gray version has a mid-range Attack value. This hardware version is positioned between the LA-2 and the LA-2A Silver (show above) build later at the end of the Sixties. The “Silver” model has a faster attack time while keeping the warm and sweet tonal characteristics of its “brothers”.

Universal Audio LA-3A
Universal Audio LA-3A

Issued at the end of the Sixties too, its building properties have been based on a very famous compressor : the 1176 LN. It offers a very nice tone and works very well on guitars, drums and even vocals.

MixCorner




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