In WaveLab there is no limitation to the use of VST plug-ins. They can be used wherever plug-ins can be inserted.
MonoToStereo turns a mono signal into a pseudo-stereo signal. The plug-in can be used on mono audio or on stereo audio with equal channels.
StereoEnhancer expands the stereo width of stereo audio material. It cannot be used with mono audio.
This plug-in is a stereo width enhancer that makes a stereo signal sound wider. It gives better results from real stereo material, as opposed to mono channels panned to different positions in the stereo image.
