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Connecting minidisc to a Scarlette optical out

Discussion in 'Recording' started by TrickySpot, Jul 8, 2015.

  1. TrickySpot

    TrickySpot Active Member

    Hi Guys, and thanks in advance for reading this!

    Generally I have a terrible habit of playing on keys and forgetting the tunes I come up with. I am also an avid collector of vintage audio equipment. Something I have never used is optical audio, but when I recently got a minidisc recorder, I thought it would be great to just pop in a minidisc an record a session of playing. I have a focusrite scarlette 18i20 audio interface which has an optical out. I linked that out to my minidisc in and the minidsic refuses to find a signal from the interface. After a bit of reading, I see you can mix multiple signals onto the scarlette's optical out. What I can't find is, are there different optical standards? If I just put a single stereo signal onto the line, why does the minidisc not detect it?

    Thanks,
    TrickySpot
     
  2. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    An optical connection can carry at least two different mutually incompatible signal types, ADAT Lightpipe and SPDIF. Lightpipe is an eight channel format that won't be recognized by a device expecting two channel SPDIF.

    The Focusrite won't automatically route its inputs to the optical output. I bet you can use the Scarlett MixControl software to route inputs to outputs. You may have to change a setting to get it to send SPDIF rather than Lightpipe.
     
  3. Boswell

    Boswell Moderator Distinguished Member

    I've not used an 18i20 for anything other than microphone inputs, but it looks from the specifications as though its optical output is ADAT only and that it's not possible to route the S/PDIF outputs via that connector as you can on most other similar interfaces. However, coax-optical converter units are cheap and work well, so I would get one of those and connect it between the phono (RCA) output of the 18i20 and the optical input of the minidisc.

    You can get the converters from Ebay shops for around a fiver or this one from Maplins for £15. Double-check that any you are looking at convert digital coax to optical Toslink and not the other way round.

    I'm sure you know that if you have one of the portable minidisc recorders you need an optical cable (lightpipe) with a Toslink connector on one end and an optical minijack plug on the other.
     
  4. TrickySpot

    TrickySpot Active Member

    Well that answers it bouldersound, the output is ADAT, so even if I try and trick the minidisc by only sending 1 channel over the ADAT (i.e. 1 channel, 7 empty), the minidisc won't see it I'm guessing because its a different standard and hence different frame structures etc. Yes Boswell, I see the problem, I would guess, and I'm going to look for it after writing this, I need an ADAT recorder. Live and learn, or live and die stupid....

    Thanks guys!
     
  5. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Is there a reason you're not recording to a computer as the interface is designed to do?
     
  6. Boswell

    Boswell Moderator Distinguished Member

    You don't need to go out and buy an ADAT recorder if you only want to record stereo (2 tracks) - a coax to optical converter is cheap and simple to use with your minidisc recorder. If were looking for an ADAT recorder, you would have to end up with something like an Alesis HD24.

    I used minidiscs for many years as a convenient portable recording medium for the occasions when it didn't matter that the information was being compressed. Along with a whole cupboard full of recorded minidiscs, I have a Denon professional minidisc system in the equipment rack in my studio, and it gets used from time to time. I still say that the ATRAC compression used in minidiscs sounds better than the MP3 compression that is universal nowadays.
     
  7. TrickySpot

    TrickySpot Active Member

    bouldersound - convenience. 99% playing around, 1% recording.....if that tunes in the 99%, I want to have a record. Why not PC? I used to run a high end Raid 0 system and after a HD failure, I lost years of work. Now I run Raid 0+1, but will never trust a PC again, get it in analog is my motto :)

    Boswell, I really just thought an optical out to a minidsic player 10 cm away would be nice, I don't see the point in converting analog to optical for such a short distance...if it went through a wall or more, then yes, but for this, just using a analog out from the scarlette to the minidisc will be fine. I think I was trying to be fancier than needed, I just need a rough audio recorder so I can recall melodies later, nothing fancy :)
     
  8. Boswell

    Boswell Moderator Distinguished Member

    I think you have missed the point. The phono (RCA) outputs of the Scarlett are not analog, they are S/PDIF digital. Using a digital output to your minidisc rather than a pair of analog outputs retains maximum signal quality and avoids your having to worry about recording signal levels.

    If, after all, signal quality is not important to you, then go for an analog connection. Remember to come back to us when you find that, whatever you do, you always get distorted recordings because the output from your Scarlett overloads the analog input of your minidisc recorder.
     
  9. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    For convenience I would go for a recorder that had inputs compatible with your keyboard output, and/or a mic. Using that interface that way seems pretty Rube Goldberg-esque.

    I usually have two drives in a tower, one system and one data, plus one external backup drive. I've never had any need for fancy RAID setups. By the time I fill up the backup drive there are newer, cheaper, bigger drives on the market that let me backup the backup and still have plenty of space for more.
     
  10. TrickySpot

    TrickySpot Active Member

    Yes, I have missed it, I still associate RCA with analog by habbit. even now it irks me to see a digital output on an old analog connector! . My minidisc doesn't have a SPDIF in, only an optical in x 2 and an analog in. If as you say I'm in for a world of pain doing it the analog route, then I'm back to an earlier post, just need a PC independent device where I can hit record and play for an hour without worrying :)
     
  11. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    SPDIF can be transmitted over coaxial cable with RCA connectors or by optical cable with Toslink connectors. The converter suggested above converts between coax and optical allowing digital connection between the RCA SPDIF output and the Toslink SPDIF input.

    I've recorded many hours of 16+ channel multitrack straight to PCs. I think your worry is disproportional to the risk. A modern solid state recorder would be more reliable than a minidisc recorder, and more convenient, and you'd be able to transfer the files digitally at full bus speed rather than in real time analog. But to each his own.
     
  12. Boswell

    Boswell Moderator Distinguished Member

    Transmission medium and data protocols are two separate things. The optical input on the minidisc recorder uses S/PDIF protocol.

    If you used a converter of the type I mentioned, you would have S/PDIF protocol being generated in logic inside the interface, coming out as electrical voltage levels on phono (RCA) connectors, going into the converter unit where it drives an LED. The LED sends light down a lightpipe that connects to the optical input of the minidisc where there is a photocell converting the light levels back to electrical signals. S/PDIF digital protocol throughout - only the transmission medium changes in the journey.
     
  13. TrickySpot

    TrickySpot Active Member

    Okay, got that all, so got the Maplin's SPDIF/Optical converter, makes sense now, made sense way earlier up the thread, just me not getting it! I do have some other teething problems, but for now I'm chuffed to have the digital working.

    I see from the "similar threads" below, I'm not the only one confused! Thanks very much guys for you patience, much appreciated!
     

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