User guide

664 User Guide and Technical Information
13
the L, R, X1, and X2 tracks are adjustable from the Setup Menu item OUTPUTS > L,R Limiter Thresh
and OUTPUTS > X1,X2 Limiter Thresh.
In normal operation, with a properly set gain structure, the threshold of the Input Limiter is rarely
reached. Without Input Limiters, high signal conditions can overload a channel and cause distortion.
The Input limiter is working when the respective input’s Input Activity LED illuminates yellow. If the
Activity LED is regularly in the yellow, reduce the amount of gain applied to the channel by turning
down the Trim control.
See Input Activity LED for additional information.
When Inputs are linked as a stereo pair, the Input Limiters are also linked and perform the same gain
reduction equally to both inputs.
The Output Limiters prevent the L,R and X1,X2 signal from exceeding the user-set limiter threshold.
Setup Menu options LIMITERS > L,R Limiter Thresh and LIMITERS > X1,X2 Limiter Thresh allow
limiter thresholds to be set set in 1 dB increments from +4 dBu to +20 dBu.
Metering
All track levels are displayed on the LCD in the Main Screen. RTN input levels are displayed on the
RTN Screen (Press the Meters bu on to toggle between the RTN Screen and the Main Screen). Each
segment of the meter represents 1 dB. A larger red square under the 20 dBU marker indicates clipping
on the track. A large yellow square indicates limiting activity on the track.
Input clipping
Limiter active
Meter Ballistics
VU
VU (volume units) meter ballistics correspond closely to how the human ear perceives loudness. This
provides a good visual indication of how loud a signal will be. In VU mode, the a ack and decay of
the meter signal is 300 mS. VU meters provide good visual indication of how loud a signal will be, but
provide poor information of actual signal peaks.
Peak + VU
The 664 can simultaneously display VU and Peak level information. In this mode the perceived loud-
ness (VU) is displayed as a standard bar, and the Peak signal as a single, independent segment above
the VU.
Input Activity LED
Each Input has its own Input Activity LED located just above the Input Fader.
The LED illuminates in various colors and intensities to represent the signal
level appearing at its respective input. Green = pre-fade signal activity, yellow
= pre- and post-fader limiter activity, red = pre- and post-fader signal overload
(peaking). Reduce the trim level control if the LEDs continuously illuminate
yellow or red. The Input Activity LED will fl ash yellow when the Input PFL is
latched. see PFL.