Grass Valley Sonata Series MADI 2010 - Manual (Page 33)

Sonata Series — Planning and Installation Manual 33
Reference Considerations
Reference Considerations
The Sonata AES-to-MADI converter must have a valid Reference signal
connected. This Reference signal is not optional. Which reference is used
will depend upon system issues and desired performance. Either the AES
(DARS) reference or the Word-Clock reference will provide the best audio
quality. A Digital Audio Reference Signal (DARS) signal is an AES3-for-
matted audio signal that is capable of being referenced, locked, and distrib-
uted at a precise audio frame rate. Word Clock is a square wave at the
sampling frequency basic rate. This signal is not standardized, however it
may be looped, and is commonly carried on coaxial cable.
The AES11 synchronization standard requires that all AES signals in a
given system are locked together so that they are all on the same sample at
the same time. The best audio performance, especially when handling sur-
round-sound signals, will occur when all channels are sample-accurate.
This accuracy can only be achieved when using AES (DARS) reference or
Word-Clock reference.
A video reference can also be used to provide a +/- 1 sample ambiguity
over a complete system for 59.94 Hz based video systems. For many 50 Hz
systems, there is no ambiguity. The audio will be locked correctly with
video reference when using video references in any digital audio system.
However, the sample delays can vary.
The supported sample-rates are as follows:
1. Video reference - 48 kHz only.
2. AES (DARS) reference - 44.1 kHz, 48 kHz, 88.2 kHz and 96 kHz.
3. Word-Clock reference - 44.1 kHz, 48 kHz, 88.2 kHz and 96 kHz.
The Sonata family Reference section automatically selects the preferred ref-
erence based upon the following priority:
1. Video reference
2. Audio reference (DARS)
3. Word Clock reference
4. First AES input reference
Note Using the first AES input reference is not recommended as a full-time refer-
ence because, if it were to fail or be switched upstream, the Sonata converter
could lose lock. This failure would affect all of the audio channels in the MADI
stream. The First AES input is should be used as a backup reference that
would be selected to if the primary reference failed.
5. MADI-to-AES and MADI-to-Analog are capable of locking to the
MADI input instead of the first AES input.