Throw one of these vst plugins on your master bus.

These VSTs will convert stereo to mono and more besides.

DFX – Monomaker

Monomaker is a simple mono-merging and stereo-recentering utility. You can use it to progressively mix down a stereo signal to mono and you can use it for equal power, center-shifting pans.

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BetaBugs – Moneo

Moneo - is a stereo plug-in which treats each channel as a separate monaural source. Each channel may then have its volume attenuated, its position in the stereo field panned, and its sonic character altered with a resonant lowor high-pass filter if you so choose. Moneo is equally comfortable with basic functionality (forcing mono) or inventive destruction of a source’s original spatial and spectral identity!

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Kelly Industries – Stereo Tools VST Plug-in

Overveiw
The Stereo Tools VST Plug-in is a simple to use utility plug-in that allows you to pan or position both the left and right channels independently of one another. This is a 2 input and 2 output plug-in. It works well for stereo files that you don’t want to have to convert to mono or if you want to fix a problem with the stereo file. For instance with the Stereo Tools plug-in you can MUTE one side of the file and then pan or position the other side to the center. You can then pan this file using the Nuendo or Cubase panner. You can also use the plug-in to remove the center information (voice remover), as well as sum both the left and right channels together. You can also work with files in the Mid/Side format.

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Related Reading:

Winning the Zero Moment of Truth - ZMOT (Enhanced Version)

PSP VintageMeter (free plug-in VST, RTAS, MAS, AudioUnit for MAC and VST, RTAS and DirectX for PC hosts) provides professional VU and PPM metering for mono and stereo tracks. All parameters like integration times and reference levels are widely adjustable to make this free plug-in suitable for any application.

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