Hey fellas, I have a PreSonus Firepod that had an RCA-style in and out for SPDIF.
My understanding is that one SPDIF input or output can carry two channels.


What I'd like to do is either be able to hook up my Roland D110 midi module to the inputs using TRS (since it's only outputs are TRS) or perhaps some sort of effects processor for guitar/bass if anyone has recommendations, and then maybe use the output for a 4 channel headphone amp.
So I'm primarily looking for ways this might be doable.

Thing is I really would like to avoid having to get a box that converts to optical, since I have limited plug space and don't really "need" SPDIF to begin with. If that's the only way I can make the connection useful, then I'd rather hook a single cable to the input and output and use it to record direct audio back into another application from SONAR.


This is my first time actually being curious about making use of SPDIF, because initially I thought it was just RCA. Any recommendations on things I can add to make use of it are welcome!

I'm still having a little trouble following your requirement, but I think you mean the following:
 
Roland D110---2xTRSout----2xRCAin---[analog-to-SPDIF]----RCAcoaxStereoSPDIF----FirePodSPDIFinput
 
An example of the mystery [analog-to-SPDIF] box is in this link at B&H's website:
[https://www.bhphotovideo.com/c/product/660217-REG/Gefen_GTV_AAUD_2_DIGAUD_GTV_AAUD_2_DIGAUD_GefenTV_Analog_to.html?ap=y&gclid=Cj0KCQjwnNvaBRCmARIsAOfZq-1-UEXICKJOi3GAZVQppYK3riEbhQPM6PPWBXGaGmQpPdoe8XjBZgIaAsmBEALw_wcB&smp=y ]
 
There are lots of little gizmos like this that can do what you want.  Your confidence in the quality of the A/D conversion, and the clock master/slave issues may drive you to reconsider, and simply get an audio interface with more analog inputs so your D110 can directly be accommodated. 

That's the thing, Ted; the Firepod has 8 inputs which is more than I'll ever need at once in the home studio, but I figured since the SPDIF is there, I might as well see if I can't make use of it.

If buying the box is unavoidable, maybe I'll just give up on the idea of using the SPDIF altogether.

The Spdif is a digital stereo input and output format. To get analog in or out of it you need another converter, like the FP itself.  So a DIGITAL drum machine w/ a digital out would a be nice addition - you could plug it right in.  Or a digital effects box.  If you wanted to up the quality of FP (I had one back in the day) you could plug a TASCAM UH-7000 in and have 2 great pres and great conversion in and out. Top flight hardware.
 
Something to watch out for is there was a flash update for the FP so you could chain 2 together, but it killed the spdif for anything but sync (is how I understood it).  If your digital doesn't work, that is probably the reason.  I don't' know how to check for that update on your unit, but Presonus probably has it onsite.
 
However, if you aren't using all 8 ins/outs now, there is really no reason to buy another converter unless you get something out of it like I listed above.  The drum machine could skip conversion, as would an effects box.  And quite frankly, the pres (and hence) the conversion (the pres are inline w/ the inputs) are 10+ years old and a bit cloudy.  However, you can make perfectly fine recordings on it with a decent mic.  The FP is better than the TASCAM 38 1/2' analog I recorded music on for national-release film incidental music and such last century.
 
@
 
 

The SPDIF is a great feature for those of us who already own gear that has SPDIF in and out. 
In my case it's my Yamaha 01V digital mixer. 
What this means is if I use the mixer I'm bypassing my audio interfaces converters and using the Yamaha's. That's all. Nice clean signal path no hums or weirdness. 
So the audio from the mixer is not being re-converted to get into my computer. 
But as said all digital devices need to be running from the same clock source so that device needs to work nicely with your system. I'm not sure I'd trust a little cheap box to do that, but you never know. 
My interface the 6i6 is really a 4x4 interface but the SPDIF gives it the extra 2 in/outs. To 99% of the people who use one I this is usless and those ports go unused mostly. My Tascam also has SPDIF, I sort of have to have that feature if I want to use the 01v. The limitation is it has had me stuck at 44.1 which is all the old 01v supports. The other downside is you will not hear the SPDIF signal in your audio interfaces headphones. 
 
Someday if I buy new powered studio monitor one feature I might want is SPDIF inputs. 
 
 

Cactus Music
But as said all digital devices need to be running from the same clock source so that device needs to work nicely with your system. I'm not sure I'd trust a little cheap box to do that, but you never know.

 
I have experience with running SPDIF connections in my setup. Currently, I run a SPDIF coax cable between my two Saffire Pro40's to pipe the headphone mix from one to the other. I also utilize another SPDIF connection to force a clock signal into my Virus Ti2. The rest of my setup is heavy in the use of ADAT optical.
 
Johnny V is right with the above statement. If the clock sources are not the same, then you will get glitches and pops.  Overall, with SPDIF (either optical TOSLINK or coax), and ADAT even, the setup must have at least one Master clock signal. Seems straight forward enough, but know that some equipment can only be a Master but not a Slave. For example, the Waldorf Q cannot accept an external clock signal, which sucks; It can only be the Master. Therefore, as another member has said, those RCA connectors go unused.
 
Also, if you decide to utilize the SPDIF coax connections in your setup, it is recommended to buy and use a 75-ohm impedance coax cable. Don't worry, they're cheap on Amazon. The 75-ohm impedance cable is different than the run-of-the-mill RCA cable. It's worth an experiment in your setup with an RCA cable if you don't want to make the $5 commitment for a proper cable, but you may get clicks, pops, and glitches and/or the device's audio may drop out or not even work at all.

S/PDIF literally stands for:  Sony Phillips Digital Interface Format
 
You can't connect analog directly to digital...
You'd need an A/D converter... taking two channels of analog and converting it to Coax (RCA) S/PDIF.
You could then feed that into the Presonus' Coax S/PDIF input.
 
When merging two digital streams of audio, keep in mind that both need to be running on the same clock (one set as Word-Clock "Master" the other a Word-Clock "Slave").
If not, you'll hear pops/ticks in the audio.

Hi. I use my POD HD500 via S/PDIF to connect it to my RME Ucx.
As mentioned, they are not normal unbalanced audio cables/connection, but digital.
All the best.

Jim Roseberry
S/PDIF literally stands for:  Sony Phillips Digital Interface Format
 
You can't connect analog directly to digital...
You'd need an A/D converter... taking two channels of analog and converting it to Coax (RCA) S/PDIF.
You could then feed that into the Presonus' Coax S/PDIF input.
 
When merging two digital streams of audio, keep in mind that both need to be running on the same clock (one set as Word-Clock "Master" the other a Word-Clock "Slave").
If not, you'll hear pops/ticks in the audio.

Don't know wether this helps but ... Reading the comments here I'm thinking it's all happened to me and what I'm seeing, is if you got analog I/Ps free and are not using them  ... Don't spend bucks you don't need to.
 
I used the Tascam FW1082 (still do from time to time) and went through all the same thing TOS boxes, A/D coverts D/A converts and they worked'ish ..  Clicking (where is that coming from?) timing problems, they were the call of the day and destroyed the creativity of my songwriting. What I'm saying is (and because of budget)  my time was spent on the tech, not the freedom of writing and producing a song! and that should be the focus ... maybe a hit!  But believe me,  all the tech doesn't help a bit

Funny thing... as of this weekend, for the first time I'm coming around to maybe having it actually be useful to use SPDIF inputs. I did a live recording/jam session with a group of friends, ended up needing all 8 inputs and could've actually used 2 - 4 more (had only 1 overhead on the drums - would loved 2 plus 2 room mics).
 
But I just realized that at that point it'd be a much better investment for me to get another Firepod for $100 and daisy-chain them together for a whole additional 8 inputs AND outputs than trying to get 2 more inputs and pay even MORE for a suitable set of electronic boxes that might not even work well if at all.
 
Can't actually justify trying to use them when there are cheaper and much better options available to me right now. See ya, SPDIF