Adventures In Audio

How to use the gain reduction meter in a compressor like the Warm Audio WA-2A Opto Compressor

by David Mellor
FREE EBOOK DOWNLOAD ► LEARN AUDIO ONLINE ►

The Warm Audio WA-2A Opto Compressor has a huge VU meter right in the middle of its faceplate. So how do you use it to measure gain reduction, and why?

Most compressors have a gain reduction meter and the Warm Audio WA-2A Opto Compressor is no exception.

It takes the form of a large VU (Volume Unit) meter which is switchable to read the output signal level or the amount of gain reduction. (The two settings for output will be an explanation for another day.)

I have to quibble about the term 'gain reduction', which is unfortunately industry standard, but confusing. I'll come to that later.

Audio Masterclass Video Courses

Learn FAST With Audio Masterclass Video Courses

With more than 900 courses on all topics audio, including almost every DAW on the market, these courses are your fast track to audio mastery.
Get a library pass for all 900+ courses for just $25.

The way a compressor works is to lower the level of loud signals while keeping the level of quiet signals the same. Thus it reduces the dynamic range of the signal. Because the peak level of the signal is now lower, most compressors have a control to bring the level back up again at the output. This may be called 'gain make-up', 'output gain', or simply 'output', or something that means the same thing.

The amount by which the level is lowered instantaneously is known as the gain reduction, and is measured in decibels. This is an important visual guide to help setting the controls of the compressor.

Too little gain reduction and you're not doing much. Too much gain reduction and the instrument or vocal will probably sound too compressed.

So 1 dB or 2 dB of gain reduction wouldn't be much, but might be enough in some situations. 20 dB of gain reduction would be a lot, and would only be used as a special effect.

Somewhere between around 5 dB and 10 dB would be useful in most contexts.

Something else the gain reduction meter will tell you is if you are compressing the signal at levels where it doesn't need to be compressed. This isn't something you hear about much, but it is important.

Suppose for instance that you set the controls of the compressor so that even when an instrument is playing at its quietest the gain reduction meter shows around 6 dB.

What this is telling you is that you are compressing signal levels that don't need to be compressed. That's not so much of a problem when the instrument is playing continuously. But if the instrument stops and starts, then each time it starts the compressor slams into 6 dB of compression before it actually gets to work. This can sound quite odd on the initial transient when the instrument starts playing.

The Audio Masterclass Pro Home Studio MiniCourse

FREE MINICOURSE

Great home recording starts with a great plan. The Audio Masterclass Pro Home Studio MiniCourse will clear your mind and set you on the right path to success, in just five minutes or less.

The answer is to back off the amount of compression so that the needle of the meter barely flinches when the instrument is playing quietly. It won't sound any less compressed, but it will avoid that slamming effect each time the instrument starts up. Of course, you can slam the compressor as a special effect. It can work quite nicely on drums, with a fast release setting.

Now, my quibble about calling the control 'gain reduction'. Gain is any change in the level of a signal, upwards or downwards. So the meter could simply be called 'gain' and the scale calibrated in negative numbers of decibels. Or it could be called level reduction, in which case it would be calibrated as the meter is in the Warm Audio WA-2A Opto Compressor. It isn't a big deal really, but my feeling is that it is good to use these expressions correctly as they apply all the way through the audio chain, whatever equipment you use, whether analog or digital.

Happy compressing!

P.S. Because this is a VU meter, it will be slower to respond than an LED bargraph could be and not follow fast peaks correctly. In the context of a compressor however, it will correspond better to the subjective loudness of the signal. Whether you would like to know the amount of gain reduction on peaks or the RMS level of the signal would be a personal preference, but in practice it wouldn't be a hardship to adapt to either.

You can learn more important audio techniques like this in the Audio Masterclass Music Production and Sound Engineering Course. Why not take a look...

Thursday November 14, 2019

Like, follow, and comment on this article at Facebook, Twitter, Reddit, Instagram or the social network of your choice.

David Mellor

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.

More from Adventures In Audio...

An interesting microphone setup for violinist Nigel Kennedy

Are you compressing too much? Here's how to tell...

If setting the gain correctly is so important, why don't mic preamplifiers have meters?

The Internet goes analogue!

How to choose an audio interface

Audio left-right test. Does it matter?

Electric guitar - compress before the amp, or after?

What is comb filtering? What does it sound like?

NEW: Audio crossfades come to Final Cut Pro X 10.4.9!

What is the difference between EQ and filters? *With Audio*

What difference will a preamp make to your recording?

Watch our video on linear phase filters and frequency response with the FabFilter Pro Q 2

Read our post on linear phase filters and frequency response with the Fabfilter Pro Q 2

Harmonic distortion with the Soundtoys Decapitator

What's the best height for studio monitors? Answer - Not too low!

What is the Red Book standard? Do I need to use it? Why?

Will floating point change the way we record?

Mixing: What is the 'Pedalboard Exception'?

The difference between mic level and line level

The problem with parallel compression that you didn't know you had. What it sounds like and how to fix it.

Compressing a snare drum to even out the level

What does parallel compression on vocals sound like?

How to automate tracks that have parallel compression

Why mono is better than stereo for recording vocals and dialogue

#