What is a VSC?


RTW's Audio Vectorscope

The Audio Vectorscope instrument (VSC) is used to evaluate the balance of stereo mixes and displays the current phase relationship between a selectable channel pair (Lissajous display) in real time. The XY coordinate representation has counter-clockwise been rotated by 45°, the point of origin has been centered on the display. Pure mono signals with exact the same level in each channel appear as vertical line with level-dependent deflection.
Signals, which are only present in the left channel, are displayed as a line rotated by 45° to the left, signals in the right channel only correspondingly by 45° to the right. If the channels have reverse polarity (one channel rotated by 180°), a horizontal line is displayed. Typical stereo mixes with proper base width appear as a well-balanced "ball of wool".

So the behaviour of the constantly moving Lissajous figure and its spreading may give information on e. g. the width of stereo base or if there are comb filter effects or phase shifts or rotations in the signal.

For surround channel configurations (5.0 and above) in TM7 and TM9 (not TMR7), the instrument in single use can be switched to a 4 channel mode. In this case, the L/R channel pair is only displayed in the two upper quadrants while the lower quadrants always show the phase relationship between the LS and RS channels of the surround signal.

to the interactive demonstration of the VSC display elements >