VU: Slow rise
and fall times. (300 ms,
Peak: Fast rise
and slow fall times. (10
ms, 500 ms)
VU meters were
designed to indicate the average program level. They are useful for
indicating the relative 'loudness' of program material. However, as
they do not respond to 'peaks', there is the possibility of overloading
the recorder circuitry (peaks can be 8-15 dB higher than the average
level). This is not so much of a problem with professional analog audio
recorders but with today's digital audio recorders and video cameras,
peak levels need to be accurately monitored.
meters (on the CS 104 and CS 106 + 1) will fully display peaks of longer
than 10 mS. Their ballistics are similar to the Nagra modulometer and
the BBC spec for PPM meters (however, with a shorter fall time). The
reference tone on the mixer is set a -8 dB below 0, therefore, peaks
of 8 dB above the average level will be displayed at 0 dB.
When using a
recorder with a VU meter, this tone should still be sent at -8 dB and
the recorder input adjusted for 0 VU. The two meters will then react
approximately the same to program material.