What is ADAT? In this article, we tell you everything you need to know. We look at the history of ADAT, how it went from being a digital recorder to an optical expansion port. We also take a look at a number of current products that use ADAT ports as a solution to increase the number of inputs and outputs of computer audio interfaces.

What Is ADAT? The History

Although these days we associate the word ADAT as a little square connector that sometimes has a little red light in the middle, it wasn’t always what we thought of when the word ADAT has mentioned in pro—audio circles.

The first time ADAT came on across the horizon was back in 1991 when at NAMM 1991, Alesis announced an 8 track digital audio recorder based on S-VHS tapes, more commonly used for video recording. The ADAT recorder and the more expensive cousin, the Tascam DA88 format that used hi-8 tapes, shared a number of features. Each machine could handle 8 tracks of digital audio and multiple machines could be linked to increase the track count. At the time they had a huge impact by bringing down the entry price for digital audio recording with the starting price when they were released in early 1992 of $3,995.

Over the years there were a number of different models produced. It started with the original ADAT (known by some as Blackface) and the ADAT XT, which both used the ADAT Type 1 format and recorded at 16 bits. Later models, the XT-20, LX-20 and M-20, offered 20-bit recording and used the ADAT Type II format.

They all used the same S-VHS tape media. Tapes recorded using the older Type I format could be used in the more modern Type II machines, but not the other way around.

Single or multiple ADAT machines could be controlled using the Alesis LRC (little remote control), which offered transport controls and the most commonly used functions. For more comprehensive control, Alesis produced the larger cousin called the BRC (big remote control), which included many more features not available on the standalone ADAT machines, such as song naming, more locate points and MIDI timecode synchronisation.

What Is ADAT? The Legacy Lives On

But what has the ADAT tape recorder got to do with the digital audio optical connector, that we know now as ADAT? One of the features of the ADAT digital audio recorders was that Alesis used the Toslink standard optical fibre cable, which was an even older digital standard invented in 1983 by Toshiba and called the TOShiba-LINK and used rectangular EIAJ/JEITA RC-5720 connectors. The Toslink format had, until then, been used for carrying the stereo SPDIF digital audio format over optical cables. But Alesis adopted the format to deliver 8 channels of digital audio at 48K/24bit and was christened officially as the ADAT Optical Interface, and more commonly known at the time, as the ADAT Lightpipe. These days it has been shortened to ADAT, formerly the name of the original digital recorders, to refer to the 8 channel digital audio optical format.

Other benefits of the ADAT lightpipe format is that it is ‘hot-pluggable’, which means devices do not need to be turned off for plugging in or unplugging, although it is recommended to mute your monitors when repatching as you can get a significant audio spike as the connection is made. The optical connection format avoids ground-loops, which can cause hum, buzz and other unpleasant audio problems.

What Is ADAT? Higher Sample Rates

The original Alesis design supported a maximum of 8 channels of 48K/24bit digital audio. To accommodate higher sample rates the Lightpipe format was modified using ‘bit-splitting’ techniques developed by a company called Sonorus. Using 'sample multiplexing', more commonly known as S/MUX, for short, this system enabled 4 channels at up to 96 kHz, or two channels at up to 192 kHz, down one optical cable. This is often why you see multiple Toslink ADAT connectors on digital audio equipment so that by using multiple optical cables the user could maintain the channel count when using higher sample rates.

What Is ADAT? How Is It Used Today?

With the ADAT Lightpipe, the original concept from Alesis of being able to easily expand your studio setup by adding units, rather than having to replace equipment, lives on long after the ADAT recorder became obsolete.

The most common application is for interface manufacturers to add ADAT ports to their interfaces to enable you to easily expand the number of inputs of your interface. For example, you might buy a small desktop interface with only a couple of mic inputs. By buying a multi-channel mic preamp unit equipped with an ADAT output you can take the number of mic inputs you can use with your DAW from 2 to 10.

What Is ADAT? Understanding Clocking Is Essential

As soon as you need to connect two or more units together digitally, you need to consider ‘clocking’. Digital audio signals have frames like video and film does. When interconnecting audio equipment digitally we have to make sure that those ‘frames’ are in sync. If you don’t, audio may pass but you will get clicks and pops. To eliminate those you need to make sure all your interconnected units are following the same clock so that all the frames start at the same time.

Clock Source Option 1

If you are connecting two units together, the simplest thing to do is to set the Clock Source of the receiving unit, to use the ADAT input as its clock source.

For example, if we are using an Apollo interface we go into the Apollo Console software Edit/Settings. You will see the dialogue box shown below.

Below we highlight some examples from past article on Production Expert in which ADAT is used to expand the IO of systems using a variety of hardware. You’ll see that while the details differ the use of ADAT is consistent throughout.

Universal Apollo Twin And Universal Audio 4-710d

In this tutorial, we show you how to set up ADAT Lightpipe input to expand the channels on the Universal Audio Apollo Twin.

The UA 4-710d offers up to 8 channels of audio inputs, 4 mic, 8 line, variable tube and transistor tone blending on 4 inputs and UA compressors. Of course, the most important thing for this is the ADAT Lightpipe out on the rear, this is what we use to connect the 4-710d to the Apollo Twin.

The connection between the 4-710d and the Apollo Twin is simple, plug the ADAT Lightpipe cable into the ADAT Out 1-8 connection on the rear of the unit, see above.

Then plug the other end of the cable into the ‘Optical In’ port on the rear of the Apollo Twin, see below.

Setting Up The Software

For digital audio units to work correctly they must all be working at the same sample rate.

The 4-170d is the master in this set-up, so first check the front of the 4-710d to check the sample rate, it is the knob on the far right below the ‘LOCK’ LED. For this set-up, we are going to use 44.1Khz. One thing to note, the Apollo Twin can only use all 8 channels if working at sample rates of either 44.1 or 48Khz. At 88.2 and 96Khz it drops to 4 channels and at 192Khz 2 channels.

Clocking

Follow the advice regarding clocking earlier in this article.

Apollo Console Display

If you have set everything up correctly then you should see an additional 8 inputs in the Apollo Console software, see below.

One thing to note, Unison plug-ins require the digitally controlled input stage of the Apollo interfaces so the ADAT interfaces will not be able to use Unison technology.

Expanding Your UAD Apollo Audio Interface With The PreSonus Digimax DP88

In this video, we show how the PreSonus Digimax DP88 can be used to expand the audio inputs of popular audio interfaces such as the Universal Audio Apollo and Focusrite units.

In this example, we expand the analog I/O with 8 additional high-quality remote preamps, using the DigiMax DP88, described by PreSonus as 'the ideal companion product for any audio interface with ADAT I/O. Check out the benefits provided by adding the DP88 to these popular interfaces.'

Focusrite Red 4Pre Interface With Audient Preamps Connected By ADAT And Word Clock

At the time James Ivey was using a Focusrite Red 4Pre as his main interface for his Pro Tools HDX rig. The Red 4 Pre offers 2 sets of ADAT ports giving a maximum of 16 channels of I/O at up to 48KHz. James used the two ADAT inputs with two Audient ASP 8 channel mic pres (ASP008 and ASP800). He ran TOSLINK cables from the ADAT out of the Audient pre-amps into the ADAT inputs on the Red 4 Pre.

He wanted to keep the Red 4Pre as his digital clock master. This meant, that in addition to the ADAT cables he also needed to run word clock cables from the Word Clock (WC) out of the Red 4 Pre to the WC input on both of the Audient Mic pre-amps but there is a problem.

The Audient pre-amps only have a WC input BNC terminal. Having consulted some of his pro-audio friends, they came up with a solution. By using a BNC T piece (which you can see in the image on the right, he fitted this onto the Word Clock output on the Red 4Pre then used two BNC cables to go to each of the two Audient pre-amps. These are then set to receive sync via Word Clock.

Check Out Some More Interfaces That Support ADAT

Check Out Some More Peripherals That Support ADAT