We get a lot of questions about ADAT expandability on audio interfaces. In today's article, we are going to cover what ADAT is and how you can use it to expand your studio.
What is it?
ADAT (Alesis Digital Audio Tape) was first created for studio use in the early 90's. They use to use a single optical cable between them to synch up the transport controls and audio playback on up to 128 tracks. This cable/connection is referred to as "ADAT Lightpipe" protocol and can send up to 8 simultaneous tracks to a recorder.
Now, I am not saying you need to use recorders from the early 90's to expand your studio. It's the lightpipe protocol that is the trick to modern multi-channel recordings.
How can I use it?
On many audio interfaces made these days, you will see something like "10 Inputs" but the interface will only have 2 mic preamps. Where are the other 8??
On this particular interface, the Audient iD22, there are two optical ports. These optical ports use the ADAT protocol from above and act as inputs and outputs for up to 8 channels of digital audio.
Being digital inputs, that means you cannot just plug in a microphone right into it. Mic level signals have to first be amplified through a preamp. At that stage it is still analog, so it must also be converted to digital audio. There are many manufacturers that solve this problem with one rack unit.
This Audient ASP800 is one among many solutions for an 8-channel preamp and converter. You don't necessarily need to spend this much to get an extra 8 channels though. There are budget options like the Behringer ADA8200 and in-betweeners like the Focusrite Scarlett OctoPre and the PreSonus DP88.
How do they work with the interface?
On the back of these type of units, there is a port of set of ports labeled, "ADAT OUT." This is where the first end of the optical cable goes. You would then connect the two units by plugging the other end of the optical cable to the ADAT IN port of your audio interface.
Now that the two units are connected, you will need to match the sample rate and setup additional inputs in your DAW. To match the sample rate, you can do one of two things. The first is just to use the preamp's internal word clock and make sure that the sample rate matches the session's sample rate.
The other option is a bit more complicated, but preferred by many engineers. You will need to go into the control panel for your audio interface. Within that panel, you can tell the interface to send out a word clock signal via that ADAT cable. That way the two units are synced to the same word clock and taking samples at the exact same time. This will reduce or even eliminate jitter that causes audible blips in the audio.
The method to setup inputs varies depending on which DAW you are using, but the idea is the same. In most cases, you will need to bring up your input grid and match the physical inputs to the software inputs.
This is a very crucial step. If you do not match the hardware inputs to software inputs, you will have no sound going to your DAW.
Why would I want this?
For engineers who need to record more than 8 channels at a time, ADAT is the best way to expand your number of inputs. Sometimes, a whole band will want to track all at once. Or if you're like me and use 16 mics on a drum kit, you easily can with the addition of a single rack piece and cable to your interface.
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