SYNCRONIZED RECORD/PLAYBACK OF 16 CHANNELS AT 24 BITS IN LOGIC AUDIO 4.0 USING STUDI/O
This application note describes how we recorded 16 channels in Logic Audio 4.0, synchronized to two ADAT XT20s via the JL Cooper dataMASTER II, and using the direct STUDI/O support built into Logic 4. Timecode recording is when you have the computer following the ADAT tape so that it records and plays back in perfect synchronization (lock step) with the tape.
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With this setup we were able to record 16 channels from the two ADAT XT20's into the computer locked to timecode. Then, we listened back to the recorded tracks, and the ADATs at the same time to make sure they were sync'd, and they were, over the whole 4 minute song!
Before we started the test, we set our audio drive up for optimal performance. This involved setting the 'Video Buffer Settings' mode of our Adaptec card to 'Cache Line' via the PowerDomain Control 4.0 software:
That ensures the SCSI card doesn't hog the PCI bus, leaving no room for audio buffers to/from Studi/o.
Next, since our Tomahawk drive had been formatted with ATTO's ExpressPro-Tools software, we ran that, and made sure the Mode Pages of the drive were optimized for 'Video'. This setting is good for any streaming media, like audio. Actually, you can use this utility even if your drives are formatted with some other software, like Apple's HD Setup.
Next, we set our System Cache (in the Memory control panel) at a moderate, fixed value. We found that 3008K was a good setting (thanks, Hiroyuki!):
Then we set our monitor color depth to Thousands of colors -- this gives a nice look to Logic without killing the PCI bus with 'fat pixels':
First, for the synchronization of the ADATs. Since direct ADAT timecode via our Sync Backplate isn't supported yet (we'll have to wait for 4.1) we'll use MIDI Timecode. Our trusty JL Cooper dataMASTER comes in handy here, translating between ADAT and MIDI sync formats. Since we don't have a USB MIDI interface yet, we got GeeThree's Stealth serial port, and used an old standard MIDI interface we had lying around.
To get Logic to send the Cooper MMC, so it can control the ADAT transports, and receive MTC, so it can sync up, we go to the Synchronization Settings window:
Set
The General tab is where we set up our tape offset (our test song starts at 4:40). When you check 'Auto enable external Sync' the Sync Mode switches automagically, which is great for transfers, but you'll need to turn it off once everything's in the computer and you want the tape machines to stop shuttling around.
In the Audio tab at the bottom we see that StudI/O defaults to 'External or Free' -- this is fine, since we're locked to the optical outputs of the ADAT.
Here we see that 'Transmit MMC' is checked -- this way the Logic transport controls the ADATs.
First, we see a couple of options just by pulling down the AUDIO menu:
If you want to monitor your inputs through Logic, check 'Auto Input Monitoring'. Note that Logic currently doesn't use the zero-latency monitoring on StudI/O, so for live punch-in's, you should monitor through your mixing board.
This is also a convenient place to set your song's sample rate.
Next, we set up the 'Audio Hardware & Drivers' Preferences:
We have StudI/O set up in dual ADAT mode (pull that menu down for other hardware configuration choices). We have set the I/O Buffer Size to the largest value (1.5K), which gives the best recording performance, and plug-in performance. But, as mentioned above, you might want a lower buffer size to reduce latency when doing live punch-ins. Be aware that this will increase the demands on your CPU and disk, however.
We're not doing mixdowns here, so we don't have a need to go from the normal 8 busses up to 16, but you can get 16 busses by checking the box. Also, you can up the total number of Audio tracks here, which is dependant only on the total system RAM you have. The memory Requirements shows how much you'll need for your new settings.
The other settings show are recommended by Emagic and seem to work the best.
Here, you see we have Logic create a waveform Overview after recording. Just a personal preference...
Next we open the Audio Window, in order to set our recording destination:
Here we set up the record Path to point to our super-fast audio disk.
There's another setting which impacts the amount of CPU time available for audio:
Un-checking 'Faster Animation' got us another track of recording on our system! The display didn't seem that much slower...
No Logic application note would be complete without at least a reference to the Environment. This powerful concept is beyond the scope of this application note, but at least we can show you the basic audio Environment set up (but we urge you to become adapt with the Environment, it's the whole key to Logic):
For recording, we set all the tracks to output from just one stereo pair, to conserve CPU cycles and get the most recorded tracks. Afterwards, you can modify the mixer, taking advantage of the busses and routing available in Logic, and taking full advantage of the outputs available on StudI/O (16 digital plus 2 analog per card -- we have 2 cards in our G3, so that's 32 digital + 4 analog outs!). As with any computer system, playback is way more efficient than recording, so once you have everything in the computer, you can get way more than 16 tracks and 16 outputs.
Download the project template we used HERE.
For more info and ideas about Logic Audio Mac 4.0 check out these sites:
Keep in mind, that these are the settings that we used to get this setup working. Your mileage may vary.
