Sound Devices 774T, Руководство пользователя и техническая информация

Страница: 70 / 82

744T User Guide and Technical Information
68
v. 2.09 Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.
Power Consumption Variables
The 744T draws power from either its on-board Li-ion battery or from external DC sources. Two
factors need to be considered to calculate battery runtime—battery/power supply capacity and unit
power consumption. The best determination of your run time is to experiment with a given record-
ing setup.
The 744T power consumption varies over a range between 4 W to 20 W (12 volts), depending on ac-
tive functions. The following functions have the most signifi cant affect on power consumption:
Inputs Active analog inputs increase power consumption. If recording from digital sources, dis-
able analog inputs, or inputs altogether to reduce power consumption. If recording solely to
inputs 1 and 2, disable inputs 3 and 4 to reduce power consumption. Analog inputs and the
microphone preamps draw current whether they are idle or active. Active inputs draw 1.5 W
compared to deactivated inputs.
Hard Drive Activity When the unit is recording to or playing back from the internal hard drive, power consumption
raises by approximately 2 W.
Microphone Powering Phantom powered microphones draw power for operation. Up to 1 W can be drawn from the
phantom supply.
Battery Chargers Depending on the charge state of the on-board Li-ion and the internal AA time code battery,
the charging circuit can draw ~10 W from external DC.
Sampling Rate The 744T draws more power at higher sampling rates. Each doubling of the sampling rate
adds ~1 W of power consumption.
Recording Time Calculation
The calculation of available 744T recording time involves three factors:
• track count - how many concurrent audio tracks are selected for recording.
• data rate - calculated from the sampling rate and bit depth for non-compressed audio and by
bit rate for data compressed audio. Data rate determines how big the data “container” is for the
audio signal (see the calculation below for determining PCM audio).
• storage capacity - typically expressed in GB
Uncompressed Recording Time in Track-Hours
Data Rate (bit depth/sampling rate), one track
16/44.1
(5.05 MB/min)
16/48
(5.49 MB/min)
24/48
(8.24 MB/min)
24/96
(16.5 MB/min)
24/192
(33.0 MB/min)
Stora
g
e
in GB
(1000 MB = 1 GB)
1 3.30 3.03 2.02 1.01 0.51
2 6.60 6.07 4.05 2.02 1.01
4 13.2 12.1 8.09 4.05 2.02
8 26.4 24.3 16.2 8.09 4.05
15 49.5 45.5 30.3 15.2 7.59
40 132 121 80.9 40.5 20.2
60 198 182 121 60.7 30.3
100 330 303 202 101 50.6
The chart above shows recording time available with the 744T. Time is expressed in hours per track
(track-hours) at the specifi ed data rate supported by the 744T. If recording two tracks, divide the
track hours fi gure by two. Similarly for four-track recording, divide track-hours by four. Note that