Mixing : Basic Mixing : Stereo Pan Depth

Stereo Pan Depth
For more information, see the following topics:
Pro Tools lets you select the pan depth for stereo output paths. You can set the Pan Depth in the Session Setup window. The Pan Depth setting lets you set the amount of signal attenuation when a track is routed to a stereo output and panned to center.
 
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On Pro Tools|HD systems only, if the Stereo Mixer plug-in is installed in the Plug-Ins folder, the Pan Depth setting defaults to –2.5 dB and cannot be changed. Move the Stereo Mixer plug-in to the Plug-Ins (Unused) folder to change the Pan Depth setting.
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The Surround Mixer requires slightly more DSP resources than the Stereo Mixer. Consequently, if you plan to regularly mix in stereo and use a Pan Depth of –2.5, you may want to use the Stereo Mixer plug-in.
To set the stereo pan depth:
1 Choose Setup > Session to open the Session Setup window.
2 Select an option from the Pan Depth selector.