Sound Devices 788T - Manual (Page 39)

Digital Inputs
The 788T accepts AES3 (AES/EBU) balanced and AESid unbalanced digital signals in professional
or consumer format via its DE-15 connector. The 788T will auto detect the type of digital signal and
adjust accordingly. Digital input gain is controlled via the front panel potentiometers.
To use a digital input, the Input Type switch located in an input’s Input Settings Window must be set
to Digital. Although a digital input signal contains a pair of inputs, the 788T is able to select just one
of the pair as an input, so for example, it is possible to select line or mic for Input 1 and digital for
Input 2.
When recording from a digital input, it is important to sync the 788T’s sample clock from a source
that is synchronous with the digital input signal otherwise audio quality will be degraded.
See Syn-
chronization. The simplest way to achieve this is to set the 788T to derive its sample clock from the
clock embedded within a digital signal. Go to the REC: SYNC REFERENCE Setup Menu and set the
sync source to the applicable digital input pair.
The LCD will display ‘D’ when locked to the selected digital input. If the Input Activity ring LEDs
are fl ashing, then a digital input is selected but no valid digital clock is being received.
AES42 Digital Microphones
The 788T is compatible with digital microphones conforming to the AES42 specifi cation, such as the
Schoeps CMD-2U. By setting DIGITAL INPUT: AES42 POWER to Enabled, the 788T supplies +10V
of “digital phantom power” to each of the digital inputs. The gain of the microphone can be adjusted
with the 788T’s front panel gain control just like a normal analog microphone. The gain adjustment is
controlled in the 788T digital domain.
Never apply digital phantom to unbalanced digital inputs, as this can result in damage to the hardware.
The 788T can lock its sample clock to a single AES42 digital microphone signal. This is set from the
Setup Menu option REC: SYNC REFERENCE to the corresponding digital inputs. When the 788T is
set to use its internal clock any connected incoming AES3 or AES42 signal is sample rate converted.
Things to consider when using AES42:
• The 788T supports four AES42 pairs.
• The 788T supports AES42 Mode 1 operation, Mode 2 operation is not supported. In other
words, the 788T supports digital audio transfer via AES42. However, it does not support the
AES42 protocol for remote control, microphone identifi cation, or status fl ag indicators. Mode 2
microphones will automatically operate in Mode 1 when connected to the 788T.
• When using multiple AES42 microphones set the REC: SYNC REFERENCE to Internal. This
will ensure a synchronous operation between the 788T and digital microphones.
Input Delay
A digital delay is selectable on each input of the 788T. Delay time per input is selectable in tenths of
a millisecond (0.1 msec) steps up to 30 msec. Each input has its own designated Input Delay Setup
Menu. If an input is turned Off, its Input Delay Setup Menu is crossed out. Delay is not set until the
Rotary Switch is pressed or the Check Mark (Tone) soft key is selected.
Input delay is limited to 15 milliseconds with sampling rates above 88.2 kHz and 7.5 seconds with sam-
pling rates above 96.096 kHz.
Input delay can be useful for time aligning input signals from differing sources. For example, digital
wireless mics that have a processing delay in their outputs. In addition, all digital conversion stages
have delay.
Inputs and Outputs
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788T/788T-SSD User Guide and Technical Information
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