The MClass Compressor

This is a single-band compressor capable of everything from subtle compression to aggressive pumping effects. Like all dynamics processors it is best used as an insert effect.

The features include “soft-knee” compression for more musical and unobtrusive compression, program-adaptive release time and a sidechain input for de-essing and other dynamics processing. Additionally, you have a CV output, allowing you to have the amount of gain reduction control other Reason Essentials parameters.

Parameters:

| Parameter	| Description
Input Gain	The Input Gain controls the ”drive” of the compression. This determines how much compression the signal will have in conjunction with the Threshold. Range: ±12 dB.
Threshold	This sets the level at which onset of compression occurs. When the input level is below the Threshold setting the signal is unaffected. When the input level exceeds the threshold, compression kicks in. In practice, this means that the lower the Threshold setting (and the higher the Input Gain), the more compression will be applied. Range: -36 dB to 0 dB
Soft Knee	Normally signals above the threshold will be compressed immediately at whatever ratio is set. This can be very noticeable, especially when using high compression ratios. When Soft Knee is activated, the onset of compression will be more gradual, producing a less drastic result.
Ratio	This lets you specify the amount of gain reduction applied to the signals above the set threshold. The Ratio can be set from 1:1 (no reduction) to ∞:1 (Infinite).
Gain meter	This shows the amount of gain reduction (in dB).
Solo Sidechain	This allows you to monitor the signal connected to the sidechain input (see below).
Attack	This governs how quickly the compressor will apply its effect when signals rise above the set threshold. If you raise this value, the response will be slower, allowing more of the signal to pass through the compressor unaffected. Typically, this is used for preserving the attacks of the sounds. Range: 1ms to 100ms.
Release	When the signal level drops below the set threshold, this determines how long it takes before the compressor lets the sound through unaffected. Set this to short values for intense, “pumping” compressor effects, or to longer values for a smoother change of the dynamics. Range: 50ms to 600ms.
Adapt Release	When this is used, set Release to the time you want for short peaks - when longer peaks occur, the Release time is automatically increased.
Output Gain	This controls the output gain and can be used to compensate for the gain reduction caused by compression. Range: ±12 dB.

About the Sidechain inputs

When a signal is connected to the Sidechain inputs, it is this signal that will trigger the compression.

This signal is not passed to the compressor output, and will thus not be heard (unless Sidechain Solo is activated).

The signal connected to the normal L/R inputs is the signal that will be processed by the compressor (as usual).

Here follows two examples of how you can use sidechain processing:

Example 1 - using the Sidechain inputs to create ducking effects

“Ducking” is when the level of one signal is reduced by the presence of another signal. A typical application is to automatically lower the level of a musical bed when a voice-over starts, and to automatically bring the level up when the voice-over stops. To set this up, we can name the musical bed in the example “Device A”, and the voice-over “Device B”. Proceed as follows:

1.	Connect Device A and Device B to separate channels on a mixer device.

In this example the signal produced by Device A should be continuous, and the signal produced by Device B should be intermittent, i.e. it should contain both silent passages and signal passages.

2.	Select Device A and then select an MClass compressor from the Create menu.

The effect will be auto-routed as an insert effect to Device A.

3.	Connect a Send on the mixer device to the Sidechain inputs on the MClass compressor.

As soon as anything is connected to the Sidechain inputs, the “Active” indicator lights up on the device panel. The compressor will no longer react to the signal produced by Device A.

4.	Turn up the corresponding AUX Send level for Device B on the mixer.

This means that the Device B signal now feeds both the mixer's input, and the sidechain input on the compressor, which in turn triggers the gain reduction.

5.	If you now start playback of both devices, the level of Device A will be lowered whenever Device B sounds, and be raised again when Device B stops.

The amount of gain reduction, how quickly it lowers the level, and the time it take for the level to return to normal again is determined by the corresponding Gain/Threshold/Ratio and Attack/Release parameters.

Example 2 - using the Sidechain inputs to create frequency sensitive compression

By inserting an equalized signal to the sidechain inputs you can make the compression more or less sensitive to a certain frequency range. A typical application of this is “de-essing” - where harsh “S”-sounds in vocal material is reduced or eliminated.

Frequency sensitive compression is set up as follows:

1.	Hold down [Shift] and create an instrument device.

Pressing [Shift] means no auto-routing connections to/from the device are made.

2.	Hold down [Shift] and create a MClass Equalizer.

3.	Hold down [Shift] and create a MClass Compressor.

4.	Create a Spider Audio Merger and Splitter device.

5.	Connect the outputs of the instrument device to the A and B inputs on the Spider.

6.	Route one pair of the split outputs of the Spider to the MClass Equalizer inputs.

7.	Route the Equalizer outputs to the Sidechain inputs on the MClass Compressor.

8.	Route another pair of the split outputs of the Spider to the MClass Compressor.

Now, the compressors normal audio inputs are fed the unprocessed signal, and the sidechain inputs are fed the equalized signal.

9.	Next, route the outputs of the Compressor to inputs on a mixer device.

10.	Activate the Solo Sidechain button on the compressor’s front panel.

You will now only hear the equalized signal.

11.	Now use the parameters on the MClass Equalizer to boost the frequencies you wish should trigger the gain reduction and cut the frequencies you wish to avoid triggering the gain reduction.

You can use rather extreme eq settings - the signal will not be heard when Solo Sidechain is deactivated anyway. E.g. for de-essing you should separate and boost the offending “S” frequencies as much as possible.

12.	Deactivate Solo Sidechain when you have finished tweaking the equalizer.

Now, the compressor will be more sensitive to the frequency area you tuned in with the equalizer, and thus react more to these frequencies. Note, however, that the whole signal will still be compressed - not just the boosted frequencies - so in case of de-essing you should usually use fast Attack and Release settings so that the gain reduction does not affect the rest of the program too much.

CV Outs

On the back of the MClass Compressor you can find a “Gain Reduction” CV out connector. This can be used to modulate other parameters with the amount of gain reduction applied by the compressor. This means that the compressor works as an envelope follower. You could for example have the audio signal level control pan in a mixer or a synth parameter.