Compressor

The Compressor is used to automatically reduce the dynamic range of the signal by squashing loud sounds and bringing up quieter sounds. For example, to smooth the level of a bass guitar or the dynamics of a vocal.

Note  The compressor and monitor mixes  When mixing live sound it is typical to set up the monitors so that they are not affected by the channel compressors. The point in the channel signal path that feeds the Aux mixes can be chosen in the Aux master Routing screen. This is set globally for each mix. The reset default setting for GLD pre-fade (monitor) sends is 'Post-PEQ' (before the compressor). You can change this using a drop-down screen menu.

Parallel Path - Lets you mix the dry path ‘uncompressed’ signal with the compressed output. This 1970’s studio technique also known as 'New York compression' is useful in live audio. By mixing the raw signal with heavily compressed material (with make-up gain) low level detail is amplified while the high level transients are preserved from the original signal.

With Parallel turned off the compressed signal is routed to the output with no input signal mixed. This is the default setting.
With Parallel turned on, the mix between ‘dry’ uncompressed and ‘wet’ compressed signal can be adjusted with independent controls.

Library - You can store and name the current Compressor settings as a preset in the Library.

Sel buttons - Hold the compressor Sel key or button to PFL (listen to) the signal after the Compressor. Touch or press Sel while holding the Copy, Paste or Reset key to copy Compressor settings to other channels or to reset it to factory default.

Compressor Type - You can select one of several different compressor emulations. Auto modes automatically adjust the attack and release according to the dynamics of the signal. In some cases this can be better for avoiding 'pumping' effects.

• Manual Peak - Offers the response of a peak based threshold detector with various smoothing, auto hold/recovery schemes to minimise distortion. The algorithm is capable of ultra fast attack time with minimal lag before onset.

• Manual RMS - Offers the response of a fairly fast pre-threshold RMS detector with added ability to manually modify the post threshold ballistics for classic sounding RMS compression with additional attack or release smoothing.

• Auto Slow Opto - Offers the response of a filament slow optical compressor.  It has reasonably slow attack with little on-set delay, and a release with non-linear exponential recovery, fast at the start and smooth for final recovery stage. This creates a smooth and musical sounding compressor.

• Auto Punchbag - Offers the response of an aggressive punch-delay compressor.  It has onset delay followed by a fast attack time and then fast recovery release to create ultimate punch in programme.

• 16T - Inspired by an industry classic VCA based RMS compressor this model produces a tight, punchy compression particularly useful with live bass and percussion and also vocals, and with a very easy to use three rotary control interface.

• 16VU -Based on an original vintage VCA based RMS compressor with VU needle meter, with pleasant characteristic sound due to its non-linearity and distortion artifacts, and also with a simple three rotary control interface.

Controls are dependent on type:

Touch and drag the curve or touch a parameter box and use the rotary to adjust compressor parameters.

Ratio - Sets the amount of compression when the signal exceeds the threshold. A ratio of 1:1 means no compression. A good starting point for vocals is around 3:1. This means a 3dB rise in level at the input of the compressor would result in a 1dB rise at its output. To use the compressor as a limiter set the ratio to 'Infinity'.

Threshold - Sets the level at which the compression starts. The meter on the left lines up with the graph and shows the signal at the input to the compressor. Start with a high setting and then dial it back until compression starts. The gain reduction meter on the right shows how much the signal is being compressed. The histogram below shows compressor activity over time.

Gain - This is 'make-up' gain which boosts the output to compensate for the drop in overall volume when the signal is being compressed. Adjust so that you hear a similar volume when switching the compressor in or out with normal signal present. Set Gain to a higher value for higher settings of Ratio and lower settings of Threshold. It is this gain that makes quiet signals sound louder.

Note If you notice the channel strip meter Pk light flashing while the meter reads low then check that you are not overdriving the Preamp while the signal is being heavily compressed. In this case back off the Preamp Gain and turn up the compressor Gain.

Soft Knee - Determines how quickly the compression cuts in. The Soft Knee adds compression gradually with more gentle ratio as it approaches the threshold level. Use this for more subtle compression of signals that hover around the threshold level.

Attack and Release - These controls set how fast the compressor pulls back the signal when it exceeds the threshold and how long it takes to let go when the signal drops below the threshold. Set this according to the type of signal to avoid hearing a 'pumping' effect.

Side Chain Filter (SCF) - Restricts the frequency range of the signal that triggers the compression. Use this to filter out low or high frequencies outside the range of the wanted signal thus preventing false triggering. Extreme settings can be used for special effect or frequency sensitive compression, for example 'de-essing' to compress just a range of high frequencies to reduce sibilance of a vocal. The default is the filter switched out.