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Interfacing problem between Roland Octa capture and Otari MX5050

Discussion in 'Recording' started by achase4u, May 23, 2015.

  1. achase4u

    achase4u Active Member

    So I wanted to run some audio to my 1/4" tape machine. The Roland manual states that there are "audio outs" in the rear of the unit - they are balanced/unbalanced jacks 1/4". TS or TRS.

    I've used them before for headphone monitoring etc. The manual states 0DBu nominal level, so I suppose this is under line level 4 dbu.

    In any case, I ran TRS males from the audio outs to XLR males into the Otari. Something is a miss, because I get no audio in the Otari. I know that in the Otari, pin 3 is hot, pin 2 is cold and pin 1 is shield. This should simply invert polarity though and not cause a total dropout. There is no audio at all.

    When I took the same cables and plugged them into my monitors, there is audio.

    When I plug directly from my preamp outputs to the line in of the Otari, I get perfectly good audio.

    What am I missing here?
     
  2. DonnyThompson

    DonnyThompson Distinguished Member

    Are you using the same cables/connectors coming out of your preamp to the Otari as you are when you are coming out of the Roland?

    I notice that there are 8 outs total on the Roland. Have you tried using any of the other outputs?

    And you're positive that the cables you are using are actual TRS to XLR and not TS to XLR? Please don't be insulted by this question, I'm just trying to help narrow down the possibilities.
     
  3. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    The roland's audio out are not preamps out. You need to acces the internal mixer of the Capture and Route either the output in the DAW or the preamps to those outputs. Open the Octa capture controle panel, chose the output pair you want to configure and do a mix of what you want to send to it (a single mic preamp, a direct mix of the preamps, or the returns from the DAW. (you might need to use hard pans to isolate a single preamp)
    Octa-Capture_direct_mix619.jpg
     
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  4. achase4u

    achase4u Active Member

    Gentlemen,

    Thank you for the replies.

    No - the cables I use from the preamp(the radial six pack) are xlr female to xlr male.

    The cables I use from the audio outs of the roland are TRS - to XLR male. I checked the boxes and they state TRS to XLR balanced. However they are molded on the TRS end, so I cannot verify what is inside and I have no cable checker. I suppose I could use the continuity short of a multimeter to check the cable.

    However, the interesting thing is that the TRS to XLR male cables in question carry the audio fine to the monitors. I also tried outputs 1/2 - not just 3/4. I did verify the routing of the Roland. I was aware that they are not preamps out. Very strange to me... even if the output of the the Roland was unbalanced, I should only see about a 6db drop over the audio to the Otari, right? I turned the line pots all the way up and don't hear a thing.

    I then took the same cables without unplugging from the Roland, and plugged them into the mic preamp section of the Otari - I then had audio. Albeit noisy as hell and an obvious mis match. I would look to the line input XLR jacks on the Otari if I hadn't just replaced them myself, as well as the fact that a preamp out gets audio just fine to the machine...
     
  5. Boswell

    Boswell Moderator Distinguished Member

    Try phase-reversing XLR barrel adaptors that have pins 2 and 3 cross-wired in to out.
     
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  6. achase4u

    achase4u Active Member

    I just realized something. I believe the Otari mic inputs and line inputs to actually not be balanced. It just struck me, there is a jumper inside the XLR. I believe it was from shield to pin 2, leaving pin 3 hot. I'll have to look in there again. The outputs of the machine are however balanced with transformers.

    So what must be happening is that the preamp out, being balanced, is still allowing pin 3 through to the input - while pin 2 of my output is shunted. I realize now that this may be bad for my preamp equipment. I hope I haven't caused any damage.

    The flip side is that the audio outs of the Roland are probably unbalanced, but are the type of jack that can accept TS or TRS. So whats happening is my only signal from the unbalanced output of the Roland is going to pin 2 hot, which on the machine is shunted.

    I will just flip the XLR jacks on this Otari so everything is in phase.

    Now here is the question - did I damage a preamp output loading half of my signal to shield? What box do I need to unbalance my signal to the Otari? Or should I add transformer circuits to the Otari input? (They have a place on the PCB for this) Will I be fighting more noise on the way in with an unbalanced signal?
     
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  7. Boswell

    Boswell Moderator Distinguished Member

    Perhaps I should have elaborated a bit more on my crossover suggestion and spelled out there that the line inputs were unbalanced (with pin 3 hot!)

    You are very unlikely to have damaged anything by driving into a short circuit. Use your nose to investigate - there will be clues there if anything has burnt out.
     
  8. achase4u

    achase4u Active Member

    Smells like(and sounds like) everything is fine.

    I wonder what scenario driving half the signal to ground is damaging? I have heard that this can "sometimes" be the case - though no specifics are given.

    Thank you!
     

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