2-8
The SDU4 contains two four element LED calibration indicators for setting of
input level.
The two input level potentiometers are set so that reference tone from the signal
source, representing the studio’s operating level, is equal to the SDU4’s internal
operating level.
Any level between –8 dBr and +8 dBr can be set to correspond with the internal
operating level. This is indicated by the two green LEDs being equally
illuminated. (0dBr = 0.775V rms.)
2.6 Output Level Setting
The SDU4 contains an internal pink noise generator that allows easy setting of
the output level controls and the verification of correct operation of the monitor
system. (Always select Dolby Surround mode before using the pink noise
generator. If unintentionally you operate the toggle switch in one of the other
modes, return it to the OFF position and select Dolby Surround to reset the
internal logic.)
The generator has two modes of operation—manual and automatic—as selected
by the front panel toggle switch. With the switch in the center, or “off” position,
the SDU4 functions normally. In the DOWN, or manual, position, wide-band
pink noise can be manually stepped to each output channel using the “noise
sequence” buttons. The manual position is typically used during initial set-up,
where correct monitor equalization is being set using a calibrated microphone
and real-time analyzer. In the UP, or auto, position the pink noise is automatically
sequenced through the output channels in two different patterns:
With the LCRS button pushed, wide-band pink noise is sequenced through all
four outputs, as done with the manual mode, except no operator intervention
is required. This is especially useful for verifying quickly correct monitor
operation.
With the CSCS button pushed, the pink noise switches between the center and
surround channels only. This allows easy and audible verification of surround
level settings by providing an audible comparison with the center-front setting.
In this mode, the pink noise is filtered to eliminate all but the mid-band
frequencies. This bandlimiting helps prevent misjudging of absolute level
caused by frequency response variations between the front and surround
speakers.
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