Mixer Signal Paths, Routing and Grouping
Below I present some mixing techniques and explanations about the main knobs and controllers from an audio Mixer.

Much of the mixers power lies in its ability to interrupt, route and re-route signals for practical or creative purposes. Each channel strip has a pan control, allowing a sound to be positioned between the left and right speakers, replicating instruments locations on a (virtual) soundstage.

To achieve this, each channel output is divided into two ‘left’ and ‘right’ outputs. If a pan control is set fully left, the right side gain will be reduced and output of the left side will be raised by a certain amount to compensate for the overall drop in level (usually +3dB). This means a stereo sound isn’t truly moved across the stereo field, so an external plugin must be used if you want to truly re-position a sound without just turning down one side of it.

Insert pun

Insert slots allow you to place a plugin effect at a certain point in the channel signal flow to alter the audio characteristics at that point. When positioned the pre-fader, the effect will occur before the channel volume fader in the signal path, so level changes will not affect the inserted device effect. This is the most common insert type and is useful for level-dependent plugins such as compressors, noise gates or distortion.

When a plugin is inserted post-fader, changes to the volume slider position affect the input level of that effect. This can be useful, say if you want a frequency analyzer display to alter when that channel volume is changed. Be aware of this difference, otherwise, you may painstakingly tweak a compressor post-fader, then turn up the fader, causing it to be compressed much harder.

By default, each of a mixer channel will travel directly to the master output fader, but sometimes it may be more practical to take a group of similar tracks for processing together using one channel strip. Drum elements, for example, are often processed as a whole. Some DAWs can now create a group channel at the click of a mouse, but a more hands-on method is to create a new channel and set its input as the outputs of the tracks you wish to group. The exact method varies from DAW to DAW, so again, break out that manual and read up on it.

Grouping tracks become even more flexible when routing groups to other groups. Route ten vocal channels as appropriate to two groups named ‘Lead Vocals’ and ‘Backing Vocals’, then send those two groups to a final Vocals group.

Sends and returns

Another feature of a mixing desk is the auxiliary send. This creates a copy of your signal either pre- or post-fader, routing as much or as little of it as you wish (controlled by the send knob) to a return channel. This routing can be sent from multiple channels and is commonly used to apply reverb, delay, etc, to a mix.

We could say, send vocals, guitar, and snare to Buss 1 in varying amounts, and set Buss 1 as the input to a new return channel. This channel will play the three elements balanced in relation to the send levels we set. If we add a reverb insert effect to the return channel, and set that reverb to 100% wet, the return channel enables us to adjust the reverb signal for the vocals, guitar and snare using a single channel strip.

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