By now, veteran Pro Tools users are aware of the track delay that can be incurred when mixing with inserted effects.

New users jump into Pro Tools to only later learn about this offset that occurs when mixing. So what is actually being delayed and how do you work around it?

When mixing inside of Pro Tools, think of the mix buss (the stereo outputs of the Pro Tools mixer) as a finish line. All audio sources (tracks) need to get to that finish line at the same time in order for everything in the mix to sound "in time" or the way in which it was intended when it was recorded. When inserting a plug-in, the audio source of that particular track has to sidetrack (or in this example "make a pit stop") before continuing to the finish line. How much time this actually takes and whether or not it's actually audible depends upon the latency incurred from the plug-in. All plug-ins are different in this regard and the answer is dependent upon how much processing power (time) is required for the plug-in to do it's job before releasing the audio back down the track. The good news is that most plug-ins accurately report this latency back to Pro Tools. In the example below, a plug-in has been inserted on the Vox track.

By Command + Click-ing on the audio volume indicator, you can toggle between the volume level of the fader, peak volume, and the total amount of delay that is being incurred on a given track. Notice the Vox track is being delayed by 415 samples while the other two tracks have no delay being incurred. Now the Vox track is late to the finish line.

Pro Tools HD systems have what's called "Delay Compensation". It uses processing power from the HD cards to compensate (do the math) for any delay that's being incurred and then make sure that all tracks, regardless of plug-in usage, reach the mix buss at the same time. In Pro Tools LE, we can do this manually by inserting the Digirack Time Adjuster plug-in on the last insert of each track. Let's be clear: What we're doing is actually delaying the other tracks to make them in time with everyone else. The goal is to make sure the delay indicator on each track is reading the same number. In this example, adding the The Time Adjuster plug-in to the other tracks will enable them to playback in time with the Vox track. They are all now in time with one another.

Delay compensation is a tricky thing and sometimes not really needed if the plug-ins in use aren't CPU hogs. But beware, the more plug-ins that are used, the more shifting around that can happen, so keep a ear out for it.