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Universal Audio LA610 Hum issue

Discussion in 'Pro Audio Equipment' started by SutraSnL, Jan 2, 2013.

  1. SutraSnL

    SutraSnL Guest

    Im running a Moog Little Phatty Stage 2 into my LA610 and from the 610 into my Yamaha 01V96 and Im getting a buzz. 2 weeks ago I wasn't...

    The exact signal flow including cables is this:
    Moog via Mogami TRS to Male XLR cable into the LA610's line input, out of the LA610's line output via Mogami Female XLR cable to TRS into my 01V96.

    I had a Neutrik NYS-SPP-L patch bay between the Moog and the LA610 in which case I used an instrument cable to connect from the Moog to the patch bay but removed the patch bay upon hearing this hum only to still get the same hum.

    When I bypass the LA610 with an instrument cable and go straight into my 01v96's preamp I dont get any kind of noise. I liked the color I got from the LA610 and was happy until this buzz showed up.

    The only thing I could think of causing this problem is the TRS isnt the right cable to be using? Do the cables have to be unbalanced? Could something be wrong with the LA610? Maybe it needs a new tube, its a few years old so could that be it?

    Thanks for any suggestion
    Clinton
     
  2. SutraSnL

    SutraSnL Guest

    So i plugged another piece into the la610 and it sounds fine. this leads me to believe theres something wrong with my moog. any ideas?
     
  3. dvdhawk

    dvdhawk Well-Known Member

    Hi Clinton welcome to RO,

    If your cable run from the synth to the LA610 isn't any longer than 15ft. - 20ft., I'd use a standard unbalanced TS instrument cable out of the Moog to the LA610's Hi-Z input and try both impedance settings on the LA610 to see which matches the Moog best. You might like the way the big fat analog synth loads the input with one impedance setting over the other. Without downloading the Moog manual to be sure, I can say very few keyboards have balanced 1/4" (TRS) outputs. And by using the TRS to XLR cable to try to create a pseudo-balanced connection I think you're introducing a variety of mis-matched levels. And more importantly, likely sending what should be the shield from the synth to pin-3 on the XLR input of the LA610. And at that point certain combinations of your phase switches in the LA610 could really create some unpredictable problems with cabling that isn't truly balanced properly. For instance, if your phase switch on the front panel is set to Out of Phase, you could be sending the shield of the synth to your LA610 output. I would also expect the "Line Level" input to be designed to accommodate a much more amplified signal than a typical synth output. Not that it wouldn't work, but I seems like it might not be optimal.


    I'm curious about post #2, what other "piece" you plugged in that gave you a better result. Was it another synth? Different manufacturers use different methods to wire 1/4" jacks. Depending on how they dealt with the Ring of the 1/4" you can get a variety of results using TS and TRS connectors. A) Some remove the contact to the Ring, when it's intended to be unbalanced - so no matter which you use TRS or TS only the Tip and Sleeve make contact. B) Some leave the Ring, but short it to the Sleeve, when it's intended to be unbalanced. C) Some equipment will leave the Ring for true balanced. and D) Some equipment provides auto-sensing circuitry to send (or receive) unbalanced signal when you short the Ring and Sleeve by using a TS cable, and send a balanced signal if you use a TRS cable. But that last one (D) is usually something you would find in a mixer, I don't think I've ever personally seen a keyboard that did that.


    If I manufactured keyboards they would have a built-in DI split with a ground lift - so I could use the balanced XLR for recording or to the snake for the FOH mixer and an unbalanced 1/4" to my keyboard amp or mixer on-stage in a live set-up. In the meantime, I build my own keyboard cases and built the DIs into the case.

    I hope that helps.
     
  4. SutraSnL

    SutraSnL Guest

    Thanks for the reply dvdhawk,
    I would have never tried the hi-z input, I figured that was reserved for guitars.

    The other "piece" is an Arturia Minibrute. I also tried my mpc1000 through it as well. Though I might add about the mpc, the right channel output is busted so I use the headphone jack. To test the mpc with the LA610, as with the Minibrute I used a balanced 1/4". I had no problems with the hum Ive described with either mpc or minibrute.

    Im going to let my Moog warm up and give the hi-z a shot! Ill let you know...

    Thanks for your help,
    Clinton
     
  5. SutraSnL

    SutraSnL Guest

    It works, thanks dvdhawk!

    I would have never thought to use the hi-z input. I cant really hear the difference in the impedance switch though.
     
  6. dvdhawk

    dvdhawk Well-Known Member

    Glad you're happy with the results.

    Although FYI, using a TRS to XLR cable from the headphone output to a mono XLR input can really cause a whole new set of problems.
    I'd be happy to bore you with the details on why that's a bad idea if you're really interested.
     

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