Installation manual

2–50 Hardware installation
48 kHz AES AUTO. This is the factory default setting and the preferred mode. This mode provides the same ultra stable
low–jitter reference at a sample rate of 48 kHz as selection #1, but has a much larger lock range of approximately + or
– 4%. When the reference is within approx. + or – 200 ppm of 48 kHz, then the DAB automatically selects the super
low–jitter secondary PLL. Otherwise, when outside the limits of + or – 200 ppm, the DAB remains locked up to a range
of + or – 4 % using only the primary PLL. When using the primary PLL, the resulting internal clocks are not as low in
jitter performance as when the secondary PLL is used, but the DAB will continue to operate correctly. When unlocked,
the internal frequency defaults to 48 kHz.
AES Automatic. This mode provides operation at all sample rate frequencies between 30 and 50 kHz. If the reference
is within approx. + or – 200 ppm of either 48 or 44.1 kHz, the DAB will automatically turn on the secondary low–jitter
PLL circuits and lock. This provides the best operation for those conditions that may have widely varying AES/EBU
references. The only problem is that when unlocked, the internal frequency defaults to something less than 30 kHz.
AES vari speed. This mode is the same as the AES Automatic mode mentioned above except that the low–jitter PLL
circuits are never enabled. This mode is mainly provided for factory test to confirm correct operation of the primary PLL
circuitry.
The options that can be selected form the rotary DIP switch are as follows:
0. 48 kHz narrow
1. 48 kHz NTSC video
2. 48 kHz PAL video
3. 48 kHz internal
4. 48 kHz AES auto
6. Not used
7. Not used
A. AES automatic
B. AES vari speed
C. Not used
D. Not used
E. Not used
Input Resolution
Input resolution refers to how many bits of sample data are used in processing the audio signals. The DAB has two options
so the user may specify which to accept. They are set with a jumper on the DAB 3500/4000 and DEX 3500 boards as
follows:
1. Force 20 bit
2. Force 24 bit (factory set – default)
20 bit
This setting uses the 20 MSB as audio data bits, and the four LSB as auxiliary data or intercom type signals. The
20 audio data bits are processed in the DSP while the 4 auxiliary bits are passed without modification.
This setting should be used when it is known that all data presented to the DAB will have 20 or less significant bits
of audio sample data.