Allen&Heath M-MADI User Manual

Page 3

digital notes

M-MADI FAQ

Q: What type of cable do I use with M-MADI and how far can it run?
A: Non-optical MADI systems use 75ohm Coaxial (video) cable terminated with BNC connectors. We tested M-MADI with typical industry cable

(Belden 1505A) with ‘Amphenol’ BNC connectors. We recommend the cables are professionally crimped using the correct tooling. When con-
necting two pieces of A&H MADI equipment, cable reach is extended from the standard 50m up to 150m with good quality cable. The key to
this feature is the receiver circuit in the MADI Option Card, so both ends of a MADI link must be A&H in order to achieve this distance. If audio
is only being transmitted to an A&H MADI card, with no audio being returned, cable length may also be extended. An RME MADI card transmit-
ting audio to an A&H MADI card will work at 150m. Distances of between 150 and 300m will also work, but as MADI dictates that transformer
isolation is not used, these longer distances require the use of a mains filter or ‘cleaner’ for each device, if the link is to remain error free dur-
ing high-voltage mains-line transients. Correct operation has been verified at 300m.
Treat coax cables with respect. Unlike touring-grade CAT5e cables, they are constructed using a solid core, which will break after repeated
bending. Ruggedised coax is available from manufacturers such as Belden, but this can be very expensive. See www.allen-heath.com for cable
recommendations.

Q: What sync options do I have with M-MADI and iLive/GLD?
A: Users can choose to take audio sync from the MADI Option Card. The normal ‘clock source’ drop-down on the touch screen or Editor pro-
gram will show ‘MixRack remote B’ (iLive) or ‘I/O Module’ (GLD), when fitted. M-MADI configuration panel has its own drop-down, for select-
ing to sync from either Link 1, Link 2, or Wordclock IN (useful in GLD and iLive fixed format systems where external sync connections are not
provided as standard). This selects which clock source is given to the system by the card.

The option to sync from the MADI stream in the mixer configuration page when a MADI Option Card is fitted is provided for convenience, and is
not part of the MADI spec. There should not be a problem with using this option, but it is outside of the spec.

When connecting Link 1 and Link 2 to two different devices, these devices must be in sync with each other, and with the iLive or GLD. This can
be achieved using a distributed word clock signal, or by syncing both devices from the MADI stream (i.e. from the MixRack), if they provide
this option. Making use of the Aux BNC as an additional word clock output can be useful here.

When using redundant mode, choosing either ‘Link 1’ or ‘Link 2’ sync merely sets the preferred input to sync from. If one link has failed, the
other will be switched to automatically.

Be careful with the AUX BNC. If the port is set to be a word clock output, and is connected to a MADI device from a 3

party, the large output

swing of the word clock could in theory damage the MADI device. For this reason, the default setting for the AUX BNC is ‘Link 1 through‘; this
mode cannot damage anything.

When in non-redundant mode, altering the input routing may produce clicks or pops on the channels being switched. Changing this routing live
is not recommended.

Using an RME MADI card as the system clock master is possible. Make sure the RME MADI card ‘Clock Mode’ is set to ‘Master’, and that the
frequency is set within the system lock range (which varies depending on whether VCO mode has been activated or not). The simplest sync

method is then to set the A&H MADI card ‘Sync Source’ to ‘Link 1’, then set the ‘Audio Clock Source’ to ‘Mix Rack Remote B’ (iLive) or ‘I/O
Module’ (GLD).

An alternative is to connect the RME card WordClock Out to the A&H MADI card Aux BNC, set the ‘Mix Rack Aux BNC’ to ‘Word Clock In’, set
the ‘Audio Clock Source’ to ‘Mix Rack Remote B’ (iLive) or ‘I/O Module’ (GLD), then set MADI card ‘Sync Source’ to ‘WordClock Input’.

Word clock source termination can be bypassed by moving the jumper fitted to CN6 from pins 1-2 to pins 2-3. This could be required when
the Aux BNC is set to output WordClock, and the receiving device is an older device using a standard CMOS input stage. If a particular receiv-
ing device is not locking to the WordClock output, the first thing to try is to see if there is a ‘term’ switch on the receiving device, and turn it off.

If this does not work, try moving the MADI card jumper as described.