Although we touched on real-time effects in Tutorial 1, I thought it might be a good idea to examine this part of PSA in a bit more detail.

As we are working with narration and location sound in this tutorial, it's natural that we give two effects a try - compression, and another powerful broadcast audio tool called a "ducker".

For a description on how to load effects, see Tutorial 1.

ADC-1 : Compression

Compressors are one of the most useful effects available to a studio, and also one of the hardest to master. In the most simplistic terms, a compressor's job is to reduce peaks in recordings, and in doing so allowing the entire track's volume to be increased, giving the track more "oompf".

ProStationAudio can make use of a software compressor plugin called the ADC-1. It has all the adjustability of a real-world hardware compressor, plus the added feature of being controlled by the automated mixing available in PSA. The ADC-1 is also unique in that it offers dual compression, and a noise gate. More on this in a moment.

Pictured below is the ADC-1's interface.

ADC-1 controls (clockwise from left) include:

• Threshold is the signal level at which the compression is triggered.
• Ratio sets the ratio of input level (pre-compression) to output level (post-compression), 1:1 means no compression, 4:1 means input peaks are being compressed to as little as one quarter their original strength, etc.
• Output is for adjusting the volume of the compressed signal signal up or down to match the rest of the mix.
• On/Off switches the effect on or off.
• Single/Dual toggles between single and dual mode.
• Release sets the speed the signal returns to its normal, uncompressed state.
• Attack controls how fast the compression is triggered.

• Threshhold is the signal level at which the gate is triggered.
• Ratio sets the ratio of input level (pre-gate) to output level (post-gate).
• On/Off switches the effect on or off.

Single Mode compression is the way most compressors operate, simply lowering points in an audio track that are above the limit defined by the Threshold setting. Standard single-mode metering is displayed at right. The bar on the right indicates the post-compression signal output. The left bar displays the threshold. The amount that the meters overlap indicates the ratio of compressed signal to non-compressed signal. Above the right bar is a clip indicator, which will light when the signal begins to distort. Often, an audible "pop" will be heard as well.

Dual Mode basically acts as a compressor/expander, with the ability to boost the signal when it falls below a certain level, as well as compressing the volume of the louder sections. Dual-mode metering (displayed at left) works in the same way as single-mode, and adds the yellow bar indicating the boosted sections of audio. I usually use this sort of effect when working with less-than-ideal source material, something like a voice recording where the person speaking is moving about in a room, while the microphone is in a fixed location. With careful use of the ADC-1 in dual mode, consistent playback of a track like this could be achieved, especially when used in conjuction with the ADC-1's gate.

A few other applications for compression and settings for the ADC-1 are listed below. Note that o'clock simply refers to the general control setting.

Here are the specific ADC-1 control values. Left/Center/Right corresponds to the control knob's position. All of the controls except Threshold are exponential; center values are given in order to give you a clearer idea of the control's values.

Truly, the best way to get to know the ADC-1 is experimentation. Load up a project and just start messing with it. For our documentary narrator's voice, a setting to give the track more definition might be in order, simlar to the setting listed second in the chart above.

This will let you get that traditional boomy announcer voice heard in radio and television commercials.

AVO-1 : Voice Over Compressor ("Ducker")

A ducker is just a volume control that is triggered by an audio source. For instance, in a documentary with music and narration, a ducker could be set to automatically compress the volume of the music track when the narrator begins to speak. This can save time for the engineer - no need to define these volume changes manually.

The AVO-1's controls (from left) include:

• Key Track selects the track used to trigger the compression.
• Threshold is the signal level at which the compression is triggered.
• Attenuation sets the ratio of input level (pre-compression) to output level (post-compression), 1:1 means no compression, 4:1 means input peaks are being compressed to as little as one quarter their original strength, etc.
• Release sets the speed the signal returns to its normal, uncompressed state.

In this tutorial's example, I loaded the AVO-1 into the track for the location sound, and keyed it to the narration track. This lowers the noise of the cows to a little better level while the narrator is speaking.

At this point, if you are happy with the mix, the session would be ready to mix down to disc for syncing to our imaginary video. For information on the mix-to-disc procedure, see Tutorial 1.