Albalá Ingenieros AAC3008C01, Руководство пользователя, Страница: 19 / 32

Albalá Ingenieros | Manual AAC3008C01
4.2.2. Normal and Silence operation
The module can deliver a stream of digital silence that can be used as a digital audio
reference signal. The phase noise (jitter) of the AAC3008C01 when using standard
sampling rates is exceptionally low, making it appropriate for use as an AES/EBU
reference signal based upon a black-burst video reference signal or a word-clock
signal.
Silencing of the channels is done via the control software with the corresponding
controls. A change to silence is not instantaneous but instead is done gradually until
the gain is at zero, or silence. These same soft transitions are used whenever the gain
of a given channel is changed.
4.2.3. Description of the delay line
The AAC3008C01 can provide an adjustable delay for each of the four digital audio
output streams. The delay is adjustable in steps of one sample and is set using the
control software. The delay that can be applied is limited by the memory available and
by the sampling frequency.
The external delay reference input (TTL DELAY) can be used to add a variable delay.
When no signal is connected to this input the added delay is 0ms. Calculation of this
variable delay is performed by measuring the time period that the delay signal is at a
logic high. The maximum delay that can be added using this input is 40ms.
The maximum possible delay for each stream, summing the programmed delay plus
the variable delay from the TTL DELAY input corresponds to 16383 samples. The
maximum delay in milliseconds for each sampling frequency is shown in the
following table:
Sampling frequency (kHz) Maximum delay (ms)
32 512
44.1 371
48 341
64 256
88.2 182
96 170
If the sum of the fixed delay and the variable delay exceeds the maximum value, then
the total delay is limited to that maximum.
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