Stephen, I guess I can say I'm pretty knowledgeable about connecting two AW4416's - AFAIK, I was the first person anywhere to do so.
I still have my two AW4416's, although they're both in storage until I finally get around to putting them on Ebay. I switched to a Yamaha board / Pro Tools setup a while ago - not primarily for sound quality reasons (the AW4416 sounds very good), but due to the comparatively slow backup speed of the AW's, and the volume of work that I do here at the studio.
Anyway, I used to get a lot of questions on how to accomplish the dual AW setup, so I wrote a little "how to" article, which was originally posted in the FAQ section of my buddy Ripe's website: http://www.socialentropy.com/aw4416
I think it will answer many of your questions, so here it is:
What's better than a Yamaha AW4416? In my opinion, it's the finest stand alone DAW currently on the market... so what could be better? How about TWO AW4416's? Why would you want or need that? Well, with two AW's you get twice as many tracks... you also have the ability to "fly" tracks from one AW into the other as needed via optional digital interface cards such as the MY8-AT or the soon to be released Waves Y56K. With this sort of setup, you can use the preamps on BOTH AW's (16 total) and route them all over to record on a single AW's 16 tracks. This requires the lightpipe cards, and is beyond the scope of what we're going to cover here, but if you're interested in how THAT'S done, let me know and I'll type something up.
Sure, you can use a single AW and an outboard preamp with a lightpipe out such as the Presonus Digimax, or use outboard preamps and a MY8-AD card and get 16 tracks recorded simultaneously on a single AW. You can also lock to a computer DAW for better editing as well as for more tracks (BTW, this is highly recommended as the best way to edit your AW tracks) or "lock up" an external digital tape deck or hard disk recorder to gain those additional tracks, but there are certain advantages to using two AW's instead. Since both AW's use the exact same software and audio format, there's only one OS to learn. You don't have to mentally "switch" between the commands for different machines while working on them, and this can be a real aid to productivity. Also, in the unlikely event that one device should require repair, tracks from either can still be loaded and played back via backup CD's from either AW4416.
Anyway, here's what you'll need:
Two AW4416's (duh!) with OS 1.3 or later installed
Two MIDI cables
One RCA/RCA format 75 ohm S/PDIF cable.
And here's how it's done:
There are two considerations when using two AW4416's together. One concerns MIDI sync of the transports and involves MTC and MMC and the second concerns word clock and digital cascade of the stereo output busses, analog cascade of aux busses if needed for cue mixes, etc... Also, as of the time of this writing, the final 2.0 AW OS software has not been released. There are some slightly differnt screens in the beta 2.0 software, and I imagine that these will remain fundementally similar in the final version of 2.0. So for now, I'm including the directions for 1.3, as well as POSSIBLE directions for 2.0. These directions work with the BETA version of 2.0 that I have available to me, but this is subject to change...
So how do I accomplish all of this? Here's the step by step instructions:
Let's call one AW "AW #1". This machine will be our MTC source as well as our word clock master for the system. It will also be the MMC slave. AW #2 will be the MTC slave, and will be a W/C slave as well. It will function as the MMC master. In other words, you'll be using the transport on this machine to control the rewinding, stop, play etc of both AW's. HOWEVER, you will still need to perform any routing, track arming, and punch in / out functions on the appropriate AW as needed.
Connect a MIDI cable from AW #1's MTC Output jack into the MIDI input of AW #2. Connect a second MIDI cable from AW #2's MIDI Out (NOT MTC OUT!) jack into AW #1's MIDI in jack. Connect a 75 ohm RCA cable from the digital out jack on AW# 1 to the digital in jack on AW #2.
You'll now be getting a error message on AW # 2.... so let's take care of that problem first. Don't worry, nothing's wrong or broken... you just have to tell AW # 2 that it should use the Word Clock data coming from AW #1 via the S/PDIF cable you just connected instead of its own internal word clock. So, press SETUP | F4 on AW #2. This is the "D. In Setup" (Digital Input setup) screen. You'll see a box labelled "D. ST In". Click on that so that the box is "dark" (ie.. select this option). In a few seconds your error message on AW #2 will stop flashing at you. Why? Because AW #2 has now been set to get its Word Clock information from AW #1 via the incoming S/PDIF signal, which is carried (along with digital audio) over the S/PDIF cable you just connected.
Word Clock has NOTHING to do with transport sync - it only concerns digital sample rates - which must remain in sync so as to avoid pops and glitches in the digital audio signals.
While you're on this page, also notice the "Stereo Bus cascade" button. You need to enable this too. This takes the signal coming in over the S/PDIF cable and routes it directly into the stereo output bus of AW #2. There's an attenuation control here as well, which you may find useful for lowering the signal of the incoming signal. Personally, I leave it full up all the time and lower the levels as needed directly from AW #1 (ie by lowering the master [red] fader, etc.) if I ever need to.
Now we need to tell AW #1 what we want sent out of that digital output and into AW #2. So on AW #1, press SETUP | F2 (Patch Out). For the "D. ST Out Assign", select "ST L/R". This sets up AW #1's S/PDIF output to send whatever is coming out the main stereo bus of AW #1 into AW #2's digital input, which we just told to route to its stereo output bus. In other words, we've now set up the two AW's so that the main stereo output of BOTH AW's are coming out of the stereo output of AW #2. At this point, anything you have connected to the stereo outputs (and appropriately routed via AW #2's setup F2 screen) such as a DAT recorder, monitor amps / speakers, etc. will receive the main stereo outputs of BOTH AW's. You can test this by pressing Play on AW #1 and hearing its stereo output come out of the headphone jack of AW #2... or out of your monitor speakers (assuming you have them connected to AW #2).
So now we've locked the word clocks and digitally cascaded the AW's, but the two transports are still not locked together. Go ahead and try it... pressing "play" on one AW doesn't make anything happen on the other one. So we need to do something about that so that anything recorded on either machine will be able to "sync" to the other machine, and so that they will play back in sync.
On AW #1, press MIDI | F2. Select MTC in the "Sync Out" section (this may show up as "MTC Sync = Master" on later AW OS versions. In OS 2.0, you'll most likely have to press MIDI | F1 to get to this page). With OS 1.3, you'll also need to select "Master" in the MTC Sync area of this same page. You will also want to select MMC Slave in the MMC section of this same page. In OS 2.0, you'll most likely find this on the same page as well (MIDI | F1).
What we've just done is to tell AW #1 that we want it to transmit MTC (MIDI Time Code), and act as the "master" time code source for both systems. We've also told it that we want it to act as a MMC (MIDI Machine Control) SLAVE. MMC is a protocol where transport commands from an external device can be used to trigger the corresponding transport functions of a second device. With the AW4416, the transport that is in MMC slave mode can still function from its own transport controls, but will also respond to incoming transport commands.
If it will respond to its own transport commands (play, rewind, etc) then why set up MMC? Because without it, you'd need to press "play" on AW #2 (which would then sit and flash at you, but not actually start playing, because it's waiting for incoming MTC sync messages to play in sync with) and THEN hit "play" on AW #1... which would then start playback, and sending out MTC messages, which AW #2 would receive, and finally, start playing in sync with. In other words, without MMC, you'd have to press play on BOTH AW's, and WITH MMC, you only have to press play on one of them (AW# 2)!
So now we have left to do is to set AW #2 to TRANSMIT MMC messages as well as to slave to incoming MTC. Here's how it's done:
Press MIDI | F2 on AW #2 (again, for OS 2.0, you'll most likely have to press MIDI | F1). Select "Sync Out=Off", "MTC Sync=Slave", and "MMC=Master". "Sync Ave." can be left "off". In OS 1.3, you'll also find the MMC Dev. (device) number "knob" on this page. Make sure that this is set to the same device number (default is 1, and that's what I use) for BOTH AW's. You also need to go to the MIDI | F1 screen of BOTH AW's (regardless of OS version) and make sure that the MIDI Tx and Rx channels are all set to the same values for Tx and Rx on BOTH machines. I use channel 1, but you can select any channel you'd like, as long as they're all set the same for BOTH AW4416's. In OS 2.0, you'll need to make all these same selections, but they'll probably all be located on the MIDI | F1 page.
One last thing. while you're in the MIDI | F2 page (MIDI | F1 on OS 2.0) you'll see a area for "Sync Offest". Offset is a way where you can tell a device to start playing at a certain timecode "point". For basic needs, you don't need to concern yourself with this. Just leave the default settings (all "zeros") for both machines.
I apologise if this seems complicated because of the different explanations for the two different Operating Systems... There are some differences between the two, and in my opinion, 2.0 is easier to use as well as having far more capabilities. Most of the things you need to adjust for locking the two AW's together with MTC and MMC can now be found on one page, instead of the two you need to access under OS 1.3. Again, this may be subject to change depending on what the "final" release version of the AW 2.0 software looks like, so let's not hold Yamaha to anything here...
Anyway, now that you've done all of this you're all set! Press "play" on AW #2. AW #1 should start playing as well. Hit Stop on AW #2 and AW #1 will also stop. If not, re-check your MIDI cable connections and device settings. Remember, it will still be necessary to hit "record" on each individual transport as and when needed, but all playback commands can be handled from just AW #2 without having to hit "play" on two different machines.
Now the only thing I have not covered is aux busses. Say you have material on one AW, and want to monitor that as well as what you're putting on to the second AW while doing overdubs. How in the world do you get the cue mixes together?
You have to use analog outputs and inputs. When it comes to aux sends and the AW, a little prior planning is in order. As you know, the AW usually has aux 7 and aux 8 assigned to the internal effects. With the Y56K, you can also use aux sends to route effects, but we'll not go into that in depth here... But deciding how to utilize your aux sends is important. I normally use aux 1-4 as effects sends for external effects (via the omni outputs) or for Y56K effects sends. I use aux 7-8 for the internal effects and that leaves me with aux 5-6, which I use for cue (headphone) feeds.
Since my studio is fairly large and has seperate isolation, tracking and control rooms, it's important for me to be able to provide a seperate headphone mix to the performers which is frequently different than what I'm listening to in the control room. I set aux 5-6 as pre-fader sends and use them as my headphoone feed.
What about outputs? Well, I use the digital output of AW #2 to feed into my computer, which is what I "mix down" to. For some of you, this isn't an issue because you "mix down" to the AW's internal stereo track and burn CD's inside of it. This is a perfectly viable option, and will be even more powerful with the addition of the Waves Y56K card's mastering effects. I hate to sound like an ad here, but the L1 Ultramaximizer is used on the mastering of the majority of albums out there these days for very good reasons... Anyway, in my opinion, the AW could have used just two more outputs, but with careful planning it has JUST enough. I use the following outputs on AW #2 (Setup | F2):
D. Stereo Out Assign = St. L/R (to computer "mixdown" deck) Stereo Out Assign = Aux 5/6 (to headphone distribution system) Omni outs are assigned to Aux 1-4 for outboard effects units...
On AW #1, I set this same page as follows:
D. Stereo Out Assign = St. L/R (to digital in of AW #2 as described earlier) Stereo Out Assign = Aux 5/6.
Now, if you route things this way, simply plug the Stereo Out of AW #1 into two analog inputs of AW #2. This brings Aux 5/6 of AW #1 into AW #2. Set those two input channels so tht they do NOT feed the stereo output bus, but so that they DO feed aux 5/6 of the second AW. Here's how to do this:
To set up the analog inputs, press Setup | F1. Select which channels you want to use on the board as your inputs. Normally I use channels 23 / 24 for this purpose, but you can use any pair you'd like. So if you're using 23/24, you'd select channels 23/24 on the Mixer Channel Input Assign area of this page and set them to "AD XX". "XX" would be whatever inputs you have the cable physically connected to. I usually use analog inputs 7 and 8, but again, you can use whatever you want.
Once you've selected channels, hit the "View" key and then press the SEL button for those channels. You should now be seeing the overall view screen for each of those channels. you may want to link those two board channels by hitting both "SEL" keys simultaneously. This will "link" those two channels. Once you've done this, make sure that you disable those channels from getting to the main stereo output bus by removing (no longer dark) the ST buttons from the Pan / Routing section of this View page. You'll also want to turn up Aux 5/6 for these two channels. By doing this, the Aux 5/6 signal from AW #1 is sent out of AW #1 via the Stereo output, comes into AW #2 via two analog inputs, does NOT get routed to the stereo output bus, but DOES get routed to the Aux 5/6 bus of AW #2, where it is mixed in with AW #2's internal Aux 5/6 signals. You can then use the aux 5/6 controls on AW #1 to acheive the proper "submix" cue feed, which you then use the channel faders of these two channles of AW #2 to blend in with the aux submix of AW #2. It's not elegant, but it does work, and it allows you to get cue signals from both AW's at the same time and send them out a common set of jacks on AW #2.
I forgot to mention that I use the MONITOR outputs as my main L/R outs to my studio main and nearfield monitors.
Additional note from ripe:
Although the AW4416 will be synchronized with MTC, people should also realize MTC only transmits absolute timing messages. This means that the both AW4416 will need their tempo set to the same value manually, this will ensure that any editing done based on BPM (measures) will match up to the same point on both AWs.
Let me know if you have any other questions, or if you're interested in a used (but well cared for) AW4416 and extra accessory goodies.