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Clocking Multiple MOTU FireWire Audio Interfaces: max tracks
Wed, 02/15/2006 - 02:00
If you are intending to use multiple MOTU FireWire audio interfaces, it works great... BUT ONLY IF you use the right clocking plan. If not, you'll be sorry. Here are my discoveries and solutions...
The safest bet is to use word clock via BNC cables. If you have just 2 interfaces, a word clock cable will do (or if you must, clock via FireWire but word is preferred).
If you have 3, definitely use word clock; you can get away with daisy chaining the word clock (in-out-in-out), although a word clock distrubution box is a good idea.
For more than 3, get a word clock distribution unit, and send clock via word clock cables directly to each MOTU FireWire interface.
MOTU's recent manuals (2005) say the following about synchronizing multiple FireWire interfaces:
Digital Performer 4:
"If you have three or more digital audio devices, you need to slave them all to a single master audio clock, such as a word clock distribution device or universal synchronizer."
...and their example scenario of just two interfaces (2408mkIII & 896) offers two choices: clocking via FireWire or via word clock.
"You can daisy-chain up to four MOTU FireWire interfaces on a single FireWire bus, with the following restrictions..."
NOTE they are not talking about CLOCKING four units together by FireWire, because in the next diagram, they show all clock carried by word clock:
"For two interfaces, slave one to the other." (word)
"You can probably get away with daisy-chaining three interfaces, although a word clock distribution device is recommended."
"[For four interfaces, daisy-chaining] is risky. A word clock distribution device is highly recommended."
I shopped around for a new clock master, and settled on the Lucid GENx6 96 Word/Super Clock Generator. It sells for under $600. Most of the other models which are BOTH a generator and a distributor were much more expensive. Be careful if you're shopping for one, because most of them in this price range are not clock generators, just distributors.
In the past, I would rent the Apogee Big Ben or the Aardvark Aardsync II when I felt I really needed it (actually, I needed it much more often than I wanted to admit). These two models have extra features not found on the GENx6 96. But the Big Ben sells for around $1350, and the Aardsync II doesn't seem to be available anymore. (The manufacturer Aardvark may be no more, possibly replaced by Antelope Audio?)
Other models out there which were at least as expensive as the Big Ben: Antelope's Isochrone OCX, the Drawmer D-Clock DSM-1 and the Rosendahl Nanoclocks/Nanosyncs.
I bought the Lucid GENx6 96 at zZounds:
Also, if you are using external mic preamps with ADAT optical outputs, such as the Focusrite OctoPre (with the Focusrite ADAT option card / ADAT/AES/SPDIF card), or the Focusrite OctoPre LE, or the Presonus Digimax, or the Presonus Digimax FS, an external clock generator is necessary to lock them to the same source clock as your MOTU system.