Here’s a question I get fairly often. Do you have digital connections on your interface? Not sure? You may have more inputs and outputs available than you realized.

Josh wrote:

Hey Joe,

I hope you had an awesome new year. I have a question about using S/PDIF inputs. I have S/PDIF I/O on my fast track pro and I was wondering if  could use these to add more recording channels for drums. I have heard they function similar to ADAT ports but I wasn’t totally sure. If you could explain to me or refer me to an article about how i could use these to expand my input channels that would be great. Maybe I have bad info and the S/PDIf have a totally different purpose but any help would be awesome.

Thanks for all your help I’ve learned so much from your posts and my acoustic guitar no longer sounds muddy thanks to your help with basic EQ.


Great question, Josh.

Here’s the “skinny.” Everything you record into your computer at some point gets converted from an analog audio signal to a digital one.

If you’re just starting out with recording, that conversion probably happens inside your audio interface. In other words, you plug your microphone or guitar directly into the interface, set the gain, and record.

But what if you had a piece of gear that converted the signal FOR you? Something like a preamp with digital outputs. What do you do with that?

That’s where digital inputs come in handy.

Most audio interfaces have some sort of digital i/o. The majority of these are one of two connections – a coaxial S/PDIF connector and an optical connector.


If you see what looks like an RCA connector on the back of your interface, chances are it’s a digital S/PDIF connection. (See picture above.)

What’s S/PDIF? It’s simply a 2-channel digital format. What does that mean? It means a single S/PDIF cable carries two channels of audio.

In Josh’s rig, he has an M-Audio Fast Track Pro. The FTP has two analog mic inputs on the front, and that’s it. What if Josh wants to use more mics? Is he stuck with two inputs? Does he have to buy a new interface if he wants more channels? No.

The Fast Track Pro has a S/PDIF input. That means Josh can buy a 2-channel preamp with a stereo S/PDIF output and record FOUR channels of audio! [*Disclaimer: I didn’t check the Fast Track Pro manual to make sure it supports 4 channels of simultaneous audio, but that’s typically how this works.]

Josh can get something like the the ART Digital MPA II. It’s a stereo preamp with S/PDIF outputs. Go look at the picture at Sweetwater’s website. You’ll see it’s got a S/PDIF output.

Josh can take a S/PDIF cable (which looks like an RCA cable) and run that from the ART to the Fast Track Pro, and BAM! he’s got 2 more mic inputs.

Optical Inputs


If you take a second look at that ART preamp. You’ll see there are also optical outputs. You may recognize these from other places. Sometimes they’re called fiber-optical connections or “lightpipe.”

Optical connections are normally one of two things – S/PDIF or ADAT. While S/PDIF is normally on a coaxial (RCA) connector, it CAN be on an optical connector. It will almost always be labeled.

If the optical connection is an ADAT signal, it can carry not two but eightchannels of audio (at 44.1 kHz or 48 kHz).

If your interface has an ADAT optical input, you can add an additional eight channels of inputs into your system (with something like a Presonus Digimax). Pretty awesome.

Mix it All Together

Now, let’s put all of this together. If you’ve got something like a 003 interface, you may think you can only record 8 inputs, since it only has 4 mic inputs and 4 line inputs.

Nope! You’ll notice it also has S/PDIF AND ADAT inputs on the back, meaning it can record 8 (analog) + 8 (ADAT) + 2 (S/PDIF) = 18 channels of audio.

This may not be new for some of you, but for those of you who don’t know about ADAT and S/PDIF, this is AWESOME stuff to know.


What digital inputs do you have on your interface? Do you even know? Take a look, leave a comment, and let us know.

What ways could you expand your input count digitally?

Big thanks to @StianSylta and @scherbi for the pics!

146 Responses to “Using S/PDIF and ADAT Inputs [Ask Joe]”

  1. Mike

    Hi Joe, i have a question for you if you can help me. I have a pro fire 2626 as host interface and i want to add two Art tubeopto8 preamps to have 16 channels for record drums. my question is, how can i connect the preamps as standalone 1 & 2 and how is the setup,, thanks for your help!

    • Joe Gilder

      Sorry Mike, I’m a little too far removed from your setup to offer advice on how to hook it up. I’d suggest reading the manuals and maybe talking to ART about it?

  2. Ricky Adams

    How’s it going? I have an issue I hope you can help me with. I have coax/ s/pdif in and out on my fire studio project interface,but my Behringer deq 2496 mastering processor has optical adat in and out; how can I connect the two best buy,amazon and fry’s all sold me the wrong converter. I need your help.

  3. dileo DJD

    Hi guys, thanks for the article Joe.

    My question is:

    does both input and output optical cables need to be connected?

    I have a fostex vm88 and i want to slave it to a Motu 828 in spdif mode, for an extra few channels. The single output optical works ok from the fostex and the sound is clear although i am getting a ticking noise thru the Motu analog output of the left channel only.
    I’ve checked all the digital connections are routed correctly internal and external etc.. but then it dawned on me that i may need the second cable to complete the information transfer? i.e word clock from motu in one cable and audio from fostex in the other…

    I hope that makes sense and i am only in need of a second cable otherwise the fostex is not working properly, maybe some bad DAC conversion???

    thanks again

      • dileo DJD

        Thanks again, as it turns out the settings on the Motu were not correct. The clock in the Motu 828 is quite specific, even tho it is set to 44.1khz, as the master there was still noise and unprocessed audio coming thru. Scrolling thru the available clock modes I found the toslink/spdif setting and bang, perfect!! This was still using the single cable. Now I have plenty of inputs for drum mics and patch inserts too, probably way too many!!! Thanks again

      • dileo DJD

        Thanks Joe, as it turns out the settings on the Motu were not right. The Motu 828 if pretty comprehensive and even tho it’s​ clock is set to 44.1khz there is still noise and unprocessed audio in the spdif setting. I scrolled thru the menu on the Motu and came across the toslink/spdif and bang!! Perfect clear audio. Toslink or Toshiba link is a version of spdif using the optical or RCA cable it was designed to improve spdif connections across multiple platforms. So all good as it turns out thanks for the info. D (this is a second reply, it looks like my first didn’t work)

  4. Aaron Liddell

    I was wondering if anyone could over me some advice.
    I have the soundcraft Si Impact mixing console. The console is a digital mixer.After exhaustive research and back and forth with sales people, and distributors, yada yada.
    Anyway my main thing is that i would like to use some of my analog outboard gear.
    Easy right… I thought it would be but here is the problem.
    The impact has NO LINE LEVEL inputs ( beside a digital source, but the user is not able to choose) and no aux sends or inserts. Well it does have 22 inserts, but you are only allowed to assign a digital source as the return.

    So i have the Si Impact which has a MADI/USB card in one expansion slot, another MADI/USB card (brand new not installed) that could go into the 2nd expansion slot, and i also have the Soundcraft Stage Box mini 16.

    I was trying to figure out how to route things so i can use my outboard gear ( API pres, Distressor, Transient Designer, 1073, Pulteq EQ, some other stuff also).

    I also have another computer i could use, if say i had a 2 DAW set up sort of like a Mastering set up (at least what my very limited knowledge vaguely envisions it to be).
    I just want to be able to use my gear in some way.

    I imagine an audio interface and maybe a small mixer could somehow solve this problem ( maybe the multi-digital card for the 2nd expansion slot of the Si Impact). I would like to somehow be able to interface the Impact and say another device that could essentially act as the expansion that now allows me to put an outboard processor on an insert, or have a line level input source. But my gut tells me that they wouldn’t be able to work that way – that is data exchange between the digital mixer and say a motu interface (just an example).

    The other crazy thought is do you think there could be a way to Mod the Impact? Of course there is a way but is it remotely probable? Looking at the schematic there is a Line level path that bypasses the pre amp/gain stage. Also regarding a mod i have enough channels that i would be good with dedicating 8-10 I/O’s to this fate permanently without them having the ability to interchange Mic level and Line level. They could be dedicated permanently to support this need.

    I am not sure if this is just too outside the box for anyone to have any advice, but no one has even tried to answer me anywhere else. I was hoping someone here might be up for the challenge.



    Si Impact Manual

    Stage Box Manual

    —- Oh yeah and i use Reaper which only will recognize 1 audio interface at a time

    • Joe Gilder

      Sorry man. I don’t know that Impact at all. It sounds like if you wanted to use a lot of outboard gear the Impact wasn’t a great choice for you. 🙂
      You can always use the outboard gear on the way IN while recording, then use plugins for your processing while mixing.

      • Aaron Liddell

        Yeah i definitely should have chosen a different mixer. I am a long time musician but complete newbie to sound engineering side of things. I researched a ton b4 purchase. TBH i was focusing on Live Sound when i purchased ( about 8 months ago) but since then have also decided to build a studio.
        Also the manual is very misleading as it continually refers to selecting Line or Mic input.

        Using it on the way in is actually what I want to do, or at least my priority regarding the outboard gear. But with no line level inputs it is hard to get into the console. If i use a pre amp signal comes in sooo hot – i have been able to gain stage accordingly with most pre’s but the pulteq eq is just way to hot to use.

        I read a ton yesterday and i am looking at a few Motu devices. I have an AES output as well as a ether link out. The thing ii am trying to figure out is if any type of digital send/return will communicate with the Impact (i.e. use a thunderbolt or fire-wire connection to connect the motu and the Impact). My instinct says that isn’t possible, but im not so sure. Thunderbolt connection on the Motu says you can Daisy chain any thunderbolt devices. I just dont know about the functionality if that is done, and i dont want to spend a GRAND to find out.

        But i could get a multi digital card and have ADAT optical and S/PDIF fire wire, thunderbolt. So if there is a way to set the devices up so that they could communicate that would be a preferred option.

        I should bite the bullet and sell the board but i really cant afford to go that route at this time.

        I Appreciate the reply though!

        • Joe Gilder

          I just think it’s really not worth it to be able to route ONE track through ONE piece of gear, y’know? It’s a lot of work for something that you may not end up using all that much. I’ve tried routing out through analog hardware, and the sonic benefits aren’t so great that it makes it worth all the time to bounce everything in realtime, and take pictures of settings, etc.

          • Jonwanez

            Its not only one track though – i run snare (57), kik, toms thru the 512 pres, and snare condensor thru the another chsnnel strip (three Q), overheads thru the trwnsient designer as well as i ick.and snare.
            Kik and snare both in distressor.

            Then drum bus through pulteq eq

        • dileo DJD

          Man that’s an awesome desk, it definitely does what you’re asking for, you need to read the manual…

          • Jonwanez

            I have read that manual more than times than Mark David Chapman read Catcher in the Rye.
            It is an awesome desk but doesnt have any line level inputs unless they are digital. And the 22 inserts can be routed from almost any channel or mixbuss mtx buss, etc. But can only return as a digital signal.

            There may be a way around it i have spent hours trying to figure it out. If you know of a silution i would be very appreciative to hear it.

            I have talked with sound craft, who just keeos saying that “it was not meant to work with outboard gear, i complained about that many times during development, maybe later models will have those capabillities.”
            No one at sweetwater has a solution and neither do a few other very seasoned engineers.

            It seems like an easy solution until u actually look into it.

            As far as reading the manual i have read it front to back many times and the PDF is literally ALWAYS one of my open windows. I have likely read that manual as much or more than anyone one the earth!

    • dileo DJD

      It looks like it has 24 inputs and 14 outputs all xlr? What is the problem!!! You send your audio thru an output routed manually or digitally, and then return it to another input, this is normal recording situation, you can record a dry signal then align another track with the outboard gear and have the wet signal, I’m sure soundcraft has thought of this, that gear is pretty good stuff

      • Jonwanez

        Yeah of course i have done that. The problem is that when u come back i to the board from any outboard gear it is too hot, bc all inputs are mic level. Some gear you are able to adjust gain, etc to control this but sometimes this defeats the sound of a particular piece of outboard. The pulteq eq on the other hand – there is no way to get the it back in with out it clipping.

        And it is my undestanding that routing things thru improper inouts like that is not good for the gear or the quality of the recording.
        I can make the source arrived at the DAW and be rcorded using outboard gesr (except the Pulteq EQ) , but it doesnt sound very good and it is usually clipping the input meter as it arrives back at the Impact from whichever outboard gear it may be, whether mic pre or como, eq, TD-4, whichever.

        What i want to do is be able to route it to something that can then send it back digitally, since the impact will recognize the digital signal as a line level.

        Im trying to figure out if thr RME router would do this, but really for the cost of that i would likely just buy another desk.

        Also since i use reaper i cant just use another audio interface bc Reaper will only recognize one at a time. So routing it to another audio interface, to outboard gear to DAW doesnt work in my situation (this also wouldnt be optimal bc i would not have any control of it at the mixing console, particularly if it was soemthing going thru a mic pre, then it would never hit the Impact.

        I am sure soundcraft thought of this. They obviously knew there was no line level inputs (non dig), i think it was the only way to offer this board at the orice point it is. Otherwise it would directly conoete with sales of both the performer and the expression.

      • Jonwanez

        Dileo – yes this ks exactly what i wwnt to do.but when it comes bwck it is line level. Then i running into the issues of noise , clipping, etc which would i imagine bw dt to impedance mismatches – is that correct?

        I want to do.somethung like you did with a notu device but i need to find the device that will allow me.to.come.back digitally, bc it will see it as a line level.

        Trust me.eceryone has thought i was just not doing it correct until they tried to he lope.fix.it then i would get “i cant belive it, or every other board you just yadda yadda”
        I could possibly run backwards thru a di but thst would just be idiotic really. Why bother. Right?

        I need to determine if either the madi or the aes are AVB compliant. If so they should be able to network with motu AVB devices.
        Any thoughts?

        • dileo DJD

          ok i see, disapointing when soundcraft tell you its not meant to be used with outboard gear, that sounds a little too inflexible. but WHY?? seems a waste to have a desk that you cant plug some vintage gear into. i didnt think it was possible. i can see you have really tried, i would imagine soundcraft would atleast make the digital component AVB compliant? i have connected a few old minidisc and cd players to the motu no probs and the tascam works great. if you could borrow something like an old cd player and that work out then it should be fine with a Motu?

          what is your DAW? are you able to record good quality audio with the soundcraft?

  5. Ronnie Wilde

    Great post Joe , really learned a lot !
    I’m setting up a studio with Focusrite Saffire 56 being the central unit.
    This is what I have:
    Saffire 56
    Octopre mk 2 dynamic
    ISA 430 producer pack
    Line 6POD pro (older rack version)
    Line 6POD pro Bass ( older rack version)

    What would be the best way to set it up?
    Adat from the octopre to the 56 for an additional 8 channels , that one I got , but what about the rest ?
    Line6 has SPDIF out and the ISA 430 has both SPDIF and ADAT.
    Of course they have all the analog I/O as well, but I’m just confused.
    Why does the ISA have adat ?
    Would love it if you could shed some lift on this .

    • Joe Gilder

      Honestly I would just plug analog out of the others into the focusrite. The more digital connections you have the more problems you will have. Analog never has sync issues. 🙂

  6. Hans Fieggen

    High Joe,

    I have a home studio where I mainly record voice-overs and audiobooks. My setup is a Neumann TLM102 into a Focusrite ISA430 Mk2 which connects to a RME Babyface Pro and onto an iMac with Hindenburg Journalist Pro as my recording software. Despite this rather high quality equipment I am not satisfied with the quality of my recordings. Allthough my voice booth is small it is acoustically sound I think (made by a professional studio builder). And after a lot of time tweaking with both the EQ on the Focusrite and on the RME it keeps giving a bit of hollowness and an “indirect” sound. Not really an echo but rather to much of a frequency which I can’t seem to filter out which makes it sound a little like I am talking through a pipe, a kind of metallic sound.

    Now in my setup the signal passes through both the preamp of the Focusrite and that of the RME and I got this idea that maybe that is the problem. Now I could buy an ADC card for the Focusrite and feed the RME through ADAT or S/PDIF (both would be possible) as to bypass the preamp of the RME. In your opinion, could that make a difference at all for the soundquality?

    • Joe Gilder

      Hi Hans. I think you’re overthinking it. The problem won’t be solved with an extra converter card. Without hearing it, I can’t say for sure, but I would guess it’s any number of things. It could be that the TLM102 doesn’t match your voice very well. It could be that you just need to learn to EQ the vocal better to make it sound amazing. It could be that your voice isn’t as good as the professional voices you’re used to hearing. I don’t know.
      But if you want to book a critique session with me and send me a clip to listen to and give some feedback, I’m happy to. Details here:

      • Hans Fieggen

        Hi Joe, thanks for your input. I think for now I will economize on new hardware 🙂 allthough I have doubts myself about the TLM102. As for the quality of my voice: of course that is rather subjective but I’ve done voice recordings in other studio’s and I just can’t seem to match the sound in my own studio with those. A matter of being a voice rather then a sound engineer I guess.

        I will send you a clip to comment on in a couple of days! Thnx!

  7. sushant sonawale

    I have Msi GL627QF laptop,it has Headphone-out (SPDIF,Focusrite Saffire Pro 24 DSP which also has SPDIF/Stereo in/out….hence technically i should be able to connect these 2 an dhave sound on speakers without any other cable attached,right?

  8. David Commey

    so then can i hook up a mixer through s/pdif to my Fast Track and get additional left and right channels?

  9. Mick

    Hi, I’m thinking of getting rme raydat pci ex card (I have a really good deal on it so it’s hard to pass) and wondering how will I be able to get sound out of it? do I need an amplifier with adat/spdif input? I don’t have any interface atm due to gear shifting.

    • Joe Gilder

      Doesn’t sound like a great deal if you don’t know how to get audio out of it….
      But I don’t know that particular device so you’ll have to do your homework, read the manual, etc.

  10. Erik Himbert

    thanks for the info! i’m sort of a newbie as well, have never figured out the adat or spdif. i’m running a Focusrite Saffire Pro 40. it is firewire only (other than adat and spdif). i recently upgraded my laptop, and no firewire port. i bought apple’s firewire to thunderbolt adapter, and it didn’t work. can i bypass firewire, and just use the adat? how would i connect the adat out to my computer?

    thanks in advance for the input!!

  11. Victor Logidasan

    hi i have zed 16fx mixer and fast track pro ,and mac system,and logic pro 9 &logic pro x
    pls do suggest what else i need to record a band with drum mics

  12. George Wiegand

    I have a Alexis I/o26 8 channel interface. And I would like to know if I can connect it to my Tascam dp-01 8 track multi track recorder? Basically I wanna know if I can use the 8 inputs on the Alexis as 8 individual tracks on the tascam? And record using the tascam. Cause I record drums usually using 4 to 6 mics. But the tascam only has 2, 1/4″ inputs and no phantom power for condenser mics. If anyone knows anything about what I’m talking about and if its possible let me know please.

  13. Ralph

    I have two old Fostex 8 Channel digital mixers with ADAT outs. I simply need at least one inexpensive ADAT to USB converter. Sounds simple right? My left testicle for a $30-$40 device. A damn shame. I wouldn’t even need an interface.

  14. Mark Emery

    I have a Yamaha i88x which has ADAT optical In/Out. My interface is a Tascam US2000 which has S/PDIF Digital in (RCA type jack) (no ADAT In) can i link them together to give me a further 8 tracks?

  15. Jose H López

    May be dumb question. So can I use 18 actual mics on my Audiobox 1818? 8 from the Audiobox, 8 from a digimax and 2 more via S/PDIF?

  16. Jorge Antonio Cárdenas Venegas

    I actually have an adat, a alesis adathd24. Could I use an interface with it, if it has an adat input? Or at least transfer the sound files that I have on the adat to my laptop? The manual, like the machine, is pretty old. And not updated to newer systems and computers. Tried with the adats Ethernet output to try to transfer the audio files to my computer. But I can not figure out how that actually works. And there’s really not much info on the web.

    • dj shadow

      Yes, you can do this. I use my old Alesis ADAT machine to bring in 8 separate audio tracks (I use the 8 tracks for 8 separate outputs of my 808 drum machine). I use the Alesis’ optical out to connect to the optical in in the Focusrite. You have to set your MixControl’s sync source to ADAT, and sample rate at 48kHz. You are right that there is not much information about how to do this on the web! I had to do a lot of trial and error to get it right.

      Oops – I forgot to mention that I use a Focusrite audio interface with the Saffire MixControl software to make these settings. If you use a different audio interface, there might be something similar for you.


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