Sound Devices 552 - Manual (Page 33)

552 User Guide and Technical Information
29
To playback a file, push the Record Controller down toward the Play position. To pause playback,
press the Record Controller. To Stop playback, press the Record Controller twice. To Rewind or Fast
Forward through a file, press and hold the Record Controller to the left or right respectively while
the file is playing back.
By default playback audio is only sent to the headphone monitor. To send the playback audio to the
Left and Right Outputs, press and hold Battery Check then press Play. After the file is stopped the
outputs will return to normal program.
Metering
The 552 features two large 21-segment LED output meters. The meters uses energy-efficient GaN
LEDs, which can be clearly seen in full sunlight. The 552 output meters are unaffected by shock, tem-
perature, or humidity extremes. The microcontroller-based meters provides a selection of ballistics
and lighting intensities.
Meter Ballistics
The output meters are capable of displaying various combinations of peak and VU ballistics: VU,
Peak, Peak and Peak Hold, a composite of VU and Peak, and a composite of Peak Hold and VU.
Meter ballistics are set in the Setup Menu. See the Setup Menu.
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 attack and
decay of the meter signal is 300 mS. VU meters provide great visual indications of how loud a signal
will be. However, VU meters provide poor information of actual signal peaks.
In VU mode, the front panel meter labeling is in volume units. VU meters are always referenced to
an actual signal level in dBu, the 552 VU meter is referenced with 0 VU corresponding to 0 dBu at the
Line-Level outputs.
Peak
Peak-reading ballistics (PPM) correspond to actual signal peaks, but don’t necessarily correspond to
perceived signal loudness. Peak meters have an instantaneous attack and a slow decay to allow the
user to visually monitor peak activity. Peak metering is useful when interconnecting to audio inputs
on digital equipment. In the digital realm, signal overload can cause immediate distortion.
The peak meter’s front panel markings are calibrated in peak dBu level at the Line Level outputs.
Peak + Peak Hold
Peak-reading ballistics correspond to actual signal peaks, but the peak value is held in the meters for
two seconds. Peak Hold indicators are useful for metering in applications when an overload condi-
tion is unacceptable.
Peak + VU
The 552 can simultaneously display VU and Peak level information. In this mode the perceived loud-
ness (VU) is displayed on a bar graph, and the Peak signal on a dot above the VU. With this combi-