HP N31.5 - Manual (Page 48)

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Madrigal Communications Link
The information needed to take full advantage of the Madrigal Communications
Linking system (MCL) falls into two categories: understanding the architecture
used, and summarizing which cables are needed between which components.
The following technical information is provided as a reference, for custom instal-
lations and other applications where a full understanding of the MCL system is
important. Most people never need this information. Feel free to skip this section
unless the basic information in Rear Panel is not sufficient to your needs.
Understanding
the Architecture
The MCL system is a single-master computer bus. As such, there must be a single
“master” component that acts as the central clearinghouse for all messages. Think
of the master component as being like the Post Office: if the Nº31.5 needs to
send a message to the Nº38S preamplifier (for example), it sends the message to
the master component, which then relays it to the preamplifier. In our system (for
a variety of technical reasons), the digital audio processor is normally designated
as the “master” for the entire chain of line-level components. (We’ll address
power amplifiers in a moment.)
This approach offers several advantages: it is quite robust and reliable; it re-
sponds extremely quickly (fast enough to seem instantaneous to the user); many
components may be added to the system without taking a performance hit; it
offers excellent forward compatibility, leaving options open to add new features
and capabilities as they become needed.
A system such as this operates with the “master” at one end of a “daisy chain.”
Subsequent components are linked together via slave in and slave out ports.
Thus, one would begin at (say) a Nº30.5, going from its master port to (say) a
Nº31.5’s slave in port; from the Nº31.5’s slave out, continue through as many
slave in/slave out ports as needed, until you reach the preamplifier.
In this fashion, multiple digital transports may be easily accommodated. The digi-
tal processor will identify which transport is connected to which digital input by
asking each in turn to momentarily turn off its DAS (digital audio signal), then
noting which input is affected. In this way, a single master can easily identify sev-
eral identical transports and still avoid any confusion. (This identification process
is called “handshaking.”)
The Mark Levinson preamplifier (Nº38 or Nº38S) serves to terminate the com-
munications bus. Hence, it receives communications from other line-level compo-
nents via it slave port. It does not have a slave out (since it terminates the bus,
it must be at the end). Since there is no way for the digital processor to perform
the digital “handshake” described above, you must rename the inputs of the
Nº38 or Nº38S appropriately
(as outlined in the manual) for Linking to oper-
ate correctly.
Thus, for example, when the Nº31.5 is turned on, the Nº30.5 comes out of
standby and selects the correct digital input, and instructs the Nº38S to wake up
and select whichever input is named “No30.” (The Nº38S may further instructs
the Nº333 to come out of standby.)