Graham over at TheRecordingRevolution.com posted a video about how to use your ADAT input on your audio interface. If you haven’t seen it yet. Go over there, watch it, then come back here.
Graham does a fantastic job of explaining this oftentimes confused topic. ADAT is a fantastic way to add an additional 8 microphone inputs to your system. (Also, if you aren’t subscribed to Graham’s site, you need to…seriously.)
While using ADAT is a killer way to expand your current rig (whether you own a 002, 003, Presonus Firestudio, etc.). However, whenever you start adding digital devices to your rig, you’re adding another level of complexity.
No, I’m not suggesting you shouldn’t add and ADAT preamp to your rig. (It can be a fantastic way to record drums.) BUT there’s one thing that could happen if you’re not careful. And it causes major headaches.
It happened to me a few years ago, and it happened to a friend of mine recently. More on that in a second.
Quick Clocking Overview
I’m not going to bore you with all the details of clocking digital devices. You simply need to know the basics so you don’t end up with jumbled digital mess.
All digital devices work at a particular “speed.” This is known as the “sample rate.” When you start connecting digital devices together (using digital connections like ADAT, AES, S/PDIF, etc.), they all need to be running at the same sample rate, or you’ll have issues.
As Graham mentioned in his video, once he connected the ADAT device to his 002, he made sure both devices are set to the same sample rate (I do everything at 44.1 kHz). Simple, right?
Another tip about digital devices – only one device can be the “master.” All the others need to be the “slave.”
In Graham’s example, either the 002 or the Behringer unit needs to be the master. There are two ways to sync up digital devices: through the digital signal itself (ADAT, AES, S/PDIF all allow for this) OR through a BNC wordclock connection. Since the 002 doesn’t have a wordclock connector, Graham has to clock the 002 to the Behringer through the ADAT cable.
Graham shows us how to do this in his video.
When Things Go Wrong
So far, we’re good. The 002 is clocking off of the Behringer via ADAT. They’re both set to the same sample rate (44.1 kHz). All is well in the world.
Where things can go wrong is if you accidentally change the sample rate of the ADAT device.
Let’s say Graham accidentally changed the Behringer’s sample rate to 48 kHz and recorded a song through the 002 into Pro Tools (which was still set to 44.1 kHz).
Everything will sound fine while recording, but let’s say Graham fixes it the next day. Now both units are at 44.1 kHz again.
When he goes to play back the tracks, they’re going to sound SLOWER than the original recording. Why? Because the audio was technically captured at 48 kHz (at the Behringer converters) and the 002 is playing them back at 44.1 kHz.
As you can imagine, this is no good at all. The song will be slower AND almost a half-step lower in pitch.
There’s no easy way to fix this. It involves importing audio into new sessions and trying to trick Pro Tools into thinking they’re at different sample rates. I won’t get into that today. Suffice it to say this is a tremendous source of frustration.
Usually you just have to re-record everything, which really stinks.
The moral of the story? Always make sure ALL of your devices are set to the same sample rate BEFORE you start recording. Make this a part of your routine before every session. It will save you much frustration…and will potentially keep you from throwing your computer out the window.
[Photo by xlibber]