Digital I/O - Any Use?

Posted by SHM Pro Audio on

S/PDIF, ADAT, AES/EBU - do these names ring any bells or do they sound like the gibberish of an infant? Even a passive observer might have seen these names on the rear panels of pro audio gears; but one thing's for sure, digital audio formats have been around for quite a while. That said, this post will take a look at their history, functionality and relevance in today's world of bedroom studios and online sensations to see if indeed they are of any use.

Many years ago, the Audio Engineering Society (AES) and the European Broadcasting Union (EBU) came together to develop a standard for digital audio exchange between audio devices. This standard known as the AES3 was first published in 1985 and it allows two channels of digital audio data to be streamed via one single XLR cable.

Prior to AES3, commercial electronics giants Sony and Phillips had come up with a similar exchange protocol for consumer audio devices called S/PDIF (Sony Phillips Digital InterFace). Physically, digital audio (PCM, Dolby digital, Dts, Dolby Surround) is sent and received through coaxial wires with RCA connectors, locally known as AV cables.

Toshiba, using the same S/PDIF protocol but changing the exchange medium used optical cables and Toslink (Toshiba Link) connectors for interfacing digital audio with their own Hi-fi electronics in 1983. Less noise and RF (radio frequency) interference are the major advantages of this medium.

As you probably expected, it didn't take too long for human greed to set in. The AES3 format is limited to just two channels, insufficient for any serious work in the digital domain, hence the Multi-channel Digital Interface (MADI) protocol was developed and can accommodate up to 64 channels at 48Khz/24bit.

An even more popular multi-channel digital audio format is the Alesis Digital Audio Tape (ADAT) lightpipe which can carry 8 channels of audio at 48Khz/24bit via a single optical cable.

The use of the MADI format in professional studios and the broadcast industry in general is evident because of their numerous ins and outs, but how handy is it to cubicle and garage-sized studios on street corners of suburban cities?

First of all, the MADI format is an overkill for most small and medium-sized studios and it's coaxial/BNC cables make it more suited for broadcast studios than music studios.

However, the AV wires used for S/PDIF connections make it friendlier to the garage studio. Hardware digital processors like the TC M350 can be used as a send/insert effect by sending digital audio from any S/PDIF bearing audio interface like the M-Track Plus to it and receiving the processed signal via the same protocol. This saves 2 to 4 analogue ports from being used.

Or maybe you just want to add an extra pair of speakers to your setup (maybe for monitoring or mastering ) without using the analogue outs of your soundcard; using a cheap DAC (digital to analogue converter) like Topping D2 with a Toslink cable to interface it with your audio interface can provide you two analogue outs for your new speakers without breaking the bank.

For owners of ADAT compatible interfaces like Focusrite Scarlett 18i20, linking it to a Behringer ADA8200 can avail you 8 analogue outputs which can be connected to a mixing desk.

More and more pro audio manufacturers are adopting the aforementioned digital audio interfacing formats in their product range because of their obvious advantages: fewer cables, less RF interference and ground loops for optical cables and more ins/outs.

Ones and zeros are the future, it will be exciting to see where subsequent advancement in this format lead us to; until then, we watch and wait.

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