Grass Valley Sonata Series MADI 2010 - Manual (Page 32)

32 Sonata Series — Planning and Installation Manual
Section 2 — Planning Guide
product, which provides a 75 ohm coax version of MADI, typically oper-
ates at distances up to 300 feet (100 meters), which is double the distance
specified in the AES10 standard.
The MADI standard requires that all 64 channels of audio are synchronous.
However, the MADI data stream isn't synchronized with a house reference;
for that reason, a reference is usually required for making and decoding
MADI streams.
There are several versions of the MADI standard in use, the most common
is the 56 channel version. There are also some MADI devices that pass 96
kHz digital audio but with half the channels supported because the 125
Mbit data-rate does not change.
Sample-Rate Conversion
Sample-rate converters, which are normally very expensive, are incorpo-
rated into the Sonata AES-to-MADI converters. These converters are pro-
vided as a cost effective way to synchronize otherwise asynchronous audio
sources such as CD players, which run at a 44.1 kHz sample rate. As well
as other playback devices that normally cannot be synchronized. These
sample-rate converters generate full 24-bit data. In addition, they can
accept signals that range of 32 kHz to 100 kHz sample rates.
The sample-rate converters are in-line for all inputs. There are provisions
for bypassing the sample rate converters. However, there are two situations
when they must be bypassed.
• The first is when a compressed audio signal such as Dolby E or Dolby
Digital is applied. The AES status block carries information as to
whether the data is normal audio or non-audio data. The Sonata AES-
to-MADI converter automatically senses the presence of this bit on an
input-by-input basis and bypasses the sample-rate converters for that
audio pair. It is acceptable to have many different audio sample rates
applied to the inputs of the Sonata converter as long as the output is
locked to a valid reference.
• The second situation is when bit-accurate MADI encoding is required.
This requirement is only possible with signals that are synchronous
with a reference. A rear panel DIP switch is provided in the Sonata con-
verter that will force the bypass of the sample-rate converters when
desired. The user may also force the rate conversion to be active when
desired. The normal setting is automatic as described above. These set-
tings are used for all 32 AES pairs.