SAM64 User Manual v1.6
14
Bel Digital Audio Limited
Frequently Asked Questions
Power:
Q: Can I run SAM64 with just one PSU (AC inlet)
cable?
A: Yes, although it is always recommended that two
AC inlet cables are connected in order to provide
a level of redundancy. The two AC inlet cables
should be connected to mains circuits which are as
independent of each other as possible.
SDI:
Q: How do you select between SDI formats?
A: SAM64 automatically determines what the
incoming SDI format is and configures itself
accordingly. Status of each individual SDI input (SD,
HD or 3G) is indicated on the front panel.
Synchronisation:
Q: SAM64 is not synchronising to wordclock.
A: Ensure that the incoming wordclock is derived
from a 75 ohm terminated source, as per the AES-
11 standard.
Q: What is the most commonly recommended
configuration for synchronisation?
A: The most commonly used and recommended
synchronisation method for SAM64 is slaving it
to wordclock via the Ref In connector. Ensure that
wordclock sync has been selected using the front
panel selection switch (WK LED should illuminate)
and that all four sample rate converter switches are
set to ON.
Q: Can I daisy-chain other devices to SAM64 to when
synchronising to Wordclock?
A: This is possible by using the wordclock loop-
through connector (WK Out). WK Out is a buffered
copy of the incoming wordclock.
Q: Can SAM64 be used as a master sync generator?
A: In the majority of installations SAM64 should
not be used as a master sync generator. The only
situation that would dictate use as a master clock
reference would be when SAM64 is synchronised
to an incoming SDI source that contains Dolby®
bitstreams. In this situation the appropriate SDI’s
Sample Rate Converter (SRC) switch should be set
to OFF and all other external audio equipment should
be synchronised to the SAM64’s wordclock output
(WK Out).
Q: Is the wordclock input terminated?
A: Yes, it is internally terminated at 75 ohms.
Sample Rate Converters:
Q: What are the Sample Rate Converters for?
A: In the traditional sense, Sample Rate Converters
(SRC) do as they say; convert an incoming or outgoing
audio source from one sample rate to another. In the
case of SAM64, the SRCs perform two functions:
a) The sample rate converters compensate for any
minor frequency differences between the incoming
SDI 48 kHz and the reference 48 kHz, thus locking
the audio to the reference 48 kHz.
b) The sample rate converters are used to phase
align the audio content within the independent
SDI sources prior to them being combined and
transmitted as a MADI stream. Unless synchronising
to an SDI source that incorporates Dolby ® encoded
material it is important to ensure that all four SRC
switches are set to ON. If set to OFF it could be
possible for audible clicks to be present on the
MADI receiving device. Note: If SAM64 detects that
phase alignment between incoming SDI streams is
significantly out (and that all SCRs are set to OFF),
SAM64 will mute the MADI output.
Q: When should an SRC switch be set to OFF?
A: The only time an SRC switch should be set to
OFF is when Dolby ® content is embedded within
the SDI stream. If this situation does arise then
SAM64 synchronisation must be set to reference
that specific SDI input. SAM64 will then become the
sync master reference source. Ensure that other
equipment then synchronises to the unit’s Wordclock
output (WK Out).
Note: only one SRC should be set to OFF at any one
time. The possibility of sync issues could arise if the
separate SDI sources are not phase aligned.
Q: Can Sample Rate Conversion be applied to the
AES outputs?
A: Yes, depending whether the SRCs are set to ON
or not. If set to OFF, synchronisation of each AES
pair will be as per the specific input SDI source.
Audio Outputs:
Q: Is there an easier way to access the AES outputs
than wiring directly to the 37-way Dsub?
A: Yes, Bel also manufacture a 1U AES3-id breakout
unit (ASBO) that connects directly to SAM64 and
provides the 32 unbalanced AES outputs on BNC
connectors (75 ohm). Contact your Bel dealer for
further information.
Q: Are the audio outputs always available?
A: Yes, de-embedded audio is simultaneously available
as 32 x AES3-id, and coaxial MADI.
Q: What fibre optic MADI cable should I use?
Recommended fibre types are 62.5/125 μm or
50/125 μm, multimode. An ST type fibre optic
connector is fitted to SAM64.
Q: I have no MADI output?
A: Check that synchronisation is valid. Audio will not
be present on the MADI output if synchronisation is
invalid (firmware version 4 and earlier only). Firmware
version 5 allows SAM64 to flywheel using its internal
sync source if an external source is lost.
