Bit Depth; Bit Depth And Dynamic Range; Synchronization; Clock Master - Sound Devices 788T-SSD User Manual And Technical Information

Bit Depth

The 788T records at bit depths of either 16 or 24 bits. 24-bit recording provides greater dynamic
range and addition headroom for signal peaks relative to 16-bit recordings. 24-bit recording (versus
16-bit) is a signifi cant benefi t for fi eld production audio tracks.

Bit Depth and Dynamic Range

Bit depth defi nes the digital "word length" used to represent a given sample. Bit depth correlates to
the maximum dynamic range that can be represented by the digital signal. Larger bit depths accom-
modate more dynamic range. A quick estimate of the maximum dynamic range capable of being
represented by a given word length is dynamic range ~= no. of bits x 6 dB. Bit depth is an exponen-
tial measure (exponent of 2), so as bit depth increases, the amount of data it represents increases
exponentially. The majority of fi eld recording is done with 16-bit audio, therefore, each sample is rep-
resented by a digital word of 2^16 (65,536) possible values. 24-bit audio has a word length of 2^24
(16.7 million) possible values per sample.
The 788T has 24-bit analog-to-digital converters. To obtain 16-bit recording the 788T can be set to
dither 24-bit digital signals to 16-bit. The 788T uses a proprietary pseudo-random dither routine
for accurate bit rate reduction. Dither can be defeated in the Bit Depth Setup Menu option. Without
dither, 24-bit audio is truncated to 16-bit, meaning the least signifi cant 8 bits are discarded.
Once a fi le is recorded its sampling rate and bit depth can not be changed in the recorder. The 788T
does not perform sample rate conversion or bit depth changes. File conversion must be done in another
environment, such as an audio workstation. Alternatively, a real-time analog transfer is often performed
instead of sample rate conversion.

Synchronization

A stable sample clock source is essential for high quality digital audio. Setups involving multiple
digital recording/playback devices often require that all devices are locked to a common clock refer-
ence to ensure they are synchronous i.e. run at the same speed and in phase with one another.
The 788T can act as a clock master, the provider of a reference clock, or as clock slave, where it locks
its internal sample clock generator to a received external master reference clock. Neglecting synchro-
nization can result in poor audio quality, sample clock timing errors, and time code drift.
The 788T uses a rock-stable sample clock and PLL circuitry to generate its internal clock frequency.
The 788T disregards word clock, AES clock and video sync during playback.

Clock Master

The 788T provides a master clock reference via its WORD OUT BNC connector or via any of its bal-
anced digital AES3 outputs. The difference between Word Out and AES is defi ned below.
788T/788T-SSD User Guide and Technical Information
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