S/PDIF input formats and methods?

I am looking into getting a stereo S/PDIF signal from a hardware mixer into Ardour. I am rather puzzled as to how this might be done. After all, most of the time, analog signals are received via an audio interface and then brought into a DAW via a USB port, right? Since I do not have an equivalent to (admittedly obsolete) ADAT devices, I am not certain how digital audio would get imported. Comment is invited!

You just need an audio interface that can handle S/PDIF input and/or output. From the computer’s and the software’s perspective, there’s no difference that the data arriving/departing in any other form (more or less).

That might involve a USB-connected device if you’re using a computer without internal expansion options (e.g. a laptop). It might involve a PCI-connected device. It doesn’t really make any difference to the computer or the software.

Since most of what I have done so far has been using the sound card to provide an analog signal to apps like Audacity and such, I didn’t know for certain at what point the waveforms get converted to digital. Thanks, Paul!

You don’t really need to know that to do what you want.

In reality, the Digital-to-Analog conversion could be in any one of several points along the way, from within the audio interface inside the computer to somewhere downstream of your mixer.

The thing to remember is that really all that matters is that your CPU (and software running on it) can read/write digital samples. Where the D/A and A/D conversions happen have some implications, but not many, and the different possibilities mostly just represent different hardware choices.

Thanks for the added details!

As far as I know there’s nothing obsolete with ADAT (I mean, we still use MIDI!).

I have an Arturia AudioFuse interface, which is supported in Linux and has ADAT input and output. It plugs via USB to my computer, and the ADAT input shows up as 8 additional inputs in ALSA. Same for output.

In my case I have a Focusrite OctoPre connected via ADAT to the AudioFuse, so it “exposes” the 8 digital inputs as 8 analog preamps. In your case, you could connect your mixer to the interface, and have it available in the 8 separate inputs.

Interesting! I only said that because I often read articles by people who write about digital audio saying that “back in the days of ADAT”, etc., and saying that these machines are now unsupported. I will check into the topic more; thanks again, Roberto!

“ADAT” can mean two things: (1) digital tape recorders (2) a protocol for tranferring (typically) 8 channels over a fiber-optic cable. Needless to say, you connected to (1) using (2) :slight_smile:

The tape recorders are indeed mostly no-longer used; the fiber optic protocol is still quite widely used.

It’s possible to get a reasonably priced ADAT to USB interface to connect an older digital mixe (in my case an Event EZbus) to a laptop. I use the miniDSP USBStreamer B. 8 tracks in/out at 24 bits/48Khz.


Hi, Dennis: thanks for the reply and added details!