S/PDIF: what's it for?

Sifunkle

Sifunkle

New member
Hi everyone,

Just a newb seeking some clarification here: what is S/PDIF used for exactly?

If I understand correctly it's for the transmission of digital audio data (rather than analog audio data which goes along most TRS, XLR etc style cables?).

So let's say in the context of a simple audio interface, would one use an S/PDIF In to, eg, import some samples from a CD being played on a CD player? Would S/PDIF Out be used to, eg, send some recorded tracks between two computers?

And if those two examples were correct... is there any particular advantage to using S/PDIF rather than just putting the CD into the computer's CD drive in the case of the former, or using a thumb USB drive to transfer files between computers in the case of the latter?

Or if I just picked on bad examples, what are some scenarios where S/PDIF is more useful than the alternatives?

Thanks in advance,

Si
 
S/pdif can be used as you described, but there's no advantage compared to putting the cd in the drive or using a flash drive.
It's still digital.

I suppose an advantage of spdif on something cheap like an mbox is that you can bypass the internal analog to digital conversion.

If you buy a super dooper fancy pre with a digital out, you're getting high quality conversion in your pre rather than low quality in the mbox.

Some effects units that i've seen have spdif out too.

I don't know the history of the format, or the 'reason' for it's existence, but i know i've found it useful on occasion.


The main selling point i suppose is that theres one less conversion in the chain.
Take an effects processor for example


If you use line ins and outs.
analog mic - digital conversion/processing- analog output from fx - then interface analog input- convert to digital.


If you use spdif it's
analog mic - digital conversion/processing then straight to the interface with no more conversion.

Think of it as one less person in the chinese whispers, or whatever the politically correct name for that is.
 
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S/Pdif is for real-time transfer of digital audio information over short distances. Say you want to record a live concert mix from a digital mixer. Rather than taking the analog output and re-digitizing it you could connect the S/Pdif from the mixer to the recorder and skip a round of digital-analog-digital conversion. It started as a consumer grade interconnection but has also been used for semi-pro recording hardware. S/Pdif signal can be transmitted over coaxial cable with RCA connectors or on optical fiber known as TOSLINK. S/Pdif is a version of the more professional AES3 (a.k.a. AES/EBU) which is generally carried over a balanced line with XLR connectors.
 
Sifunkle said:
So let's say in the context of a simple audio interface, would one use an S/PDIF In to, eg, import some samples from a CD being played on a CD player?
Click to expand...

taking advantage of your S/PDIF in would allow you to add simultaneous ins from another device.

Sifunkle said:
Would S/PDIF Out be used to, eg, send some recorded tracks between two computers?
Click to expand...

taking advantage of your S/PDIF out would allow you to add the ins from your interface to another device.

for instance, i run 2 Motu 8pres. they each have 8 XLR inputs with phantom power and preamps. i connect them with S/PDIF lightpipe cables and they act as one interface allowing me to record 16 tracks simultaneously (which i've never done)
 
From the OP's post, I think he understands the question better than he thinks he does.

S/PDIF is just a format for transmitting digital data (specifically digital audio data) from one box to another. There's no particular advantage to it vs. any other method of transmitting digital audio data directly from one box to another.

The scenario where it's most useful is: you have a box with an S/PDIF out and another box with an S/PDIF in, you want to move digital audio data from the first to the second, and there's not a more convenient way to connect them (or to move the data by way of a intermediate step, such as copying it to a thumb drive).

That's about it.

If you want to compare it to methods of transmitting analog audio data, there's more to talk about, but you're also talking about a whole different subject.
 
Thanks for all the replies everyone, much clearer now!

I think I was mostly at the stage of understanding how the thing worked, but not the applications it would be used for. To summarise what I've gathered from your replies: S/PDIF is mostly useful for avoiding unnecessary digital-analog conversion that would deteriorate the sound quality, and can also be used to daisy-chain devices together!

Please let me know if I've got that completely wrong, but otherwise thanks very much for your help!
 
Yeah SPDIF is how I connect my Lucid Converter to my Firestudio to add 2 more channels to my rig. Its pretty nice. Not only is it a better converter but it gives me 10 channels instead of 8.
 
I think it's pretty much true by definition that any method of transferring digital data is "mostly useful for avoiding unnecessary digital-analog conversion."

S/PDIF is not particularly useful for daisy-chaining devices together.

The key characteristics of S/PDIF that make it preferably or not preferable in a particular situation vis-a-vis some other method of transferring the same digital data:
- It's real time.
- It uses an S/PDIF output jack and an S/PDIF input jack.

The first is sometimes relevant. The second is really the big one: for example, if you've got, say, a standalone AD converter with only an S/PDIF output jack (no USB or Firewire or whatever), you're probably going to want to use an S/PDIF input jack on the device you want to connect it to.
 
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