Hello,
Just a simple question. I've been working on a simple setup for years with my instruments connected directly to interface via either a preamp, guitarcab or for synths, as midi.
I'm just wondering what the ADAT and spdif is used for in audio production and what can be gained by advancing for products etc that use these kind of connections ?

more inputs!
 
I don't use them myself, but you can get something like the Focusrite Octo Pre which would give you 8 more mic inputs, use ADAT out from the Octopre to ADAT in to your soundcard.
 
same for SPDIF, but you only get 2 extra channels with it (typical)

My Lexicon 300 reverb can be connected via S/PDIF, which frees up an analog I/O pair on my audio interface.
Which is good when you have too much analog synth gear... 

Thanks guys. I guess for now then it wouldn't be of any use since I only fill up 5 inputs on my 8ch interface. Maybe when I get professional in another life it will come in handy :)

I use S/PDIF to record outboard synths with an extremely low noise floor.

You don`t have to be professional to use adat :D If you need you use :D