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Dumb Cable Question # 613

Discussion in 'Accessories / Connections' started by mark4man, Nov 14, 2004.

  1. mark4man

    mark4man Active Member

    Kurt (or anybody),

    I should know this...but I'm not functioning too well this evening.

    After years of dorkin' around with preamps & ISO Xformers & Step-Up Xformers, etc., etc...I've found that the best sounding signal out of my sound module occurs when I just plug the damn thing in to the Audio Interface (& all this after I just dropped two grand on a preamp (#*!%&~.) Oh well, it's still the best mic pre I've ever heard...so all is not lost.)

    Anyway...the synth module of course has an unbalanced, -10dBV output; & sounds best when I connect it via a Monster TS to TS right into the AI's input.

    My new pre (of course), has a balanced XLR line input; but I'd like to take one more shot at amping up the synth.

    My question is: I know there's such a thing as unbalanced to balanced cables (& adapters.) But what happens between the double & triple pin configs; & where? Is it 2 to 3 at the balanced end? 3 to 2 at the unbalanced end? Is one shunted to ground? How does this work?

    Thanks,

    mark4man
     
  2. stickjam

    stickjam Guest

    None of the above. The standard for 99% of balanced XLR connectors is 1=ground, 2=hot (signal in phase) 3=cold (signal 180 degrees out of phase) Connecting pins 2 and 3 together ensures you'll get nothing. :) Be aware that a few odd, usually older, pieces of gear has pin-3-hot and pin-2-cold.

    To make an unbalanced 1/4" to XLR cable, you would want to connect the tip to the hot pin (2) and connect the sleeve (shield) to both pins 1 and 3. Make sure you know which pins on an XLR are which--they're usually marked with microscopically small numbers and counterintuitively, 1-2-3 isn't in a clockwise (or counterclockwise) progression.

    However, your question poses a dilemma I've always wondered, so for anyone else (Kurt? 8) )... 1.) When connecting an unbalanced source to a balanced input, is it better to strap pins 1 and 3 at the input, or run all three lines through the cable and tie the cold to shield at the unbalanced output? 2.) Does it make a difference if the roles are reversed; a balanced output into an unbalanced input?

    -Bob

    PS. Before connecting an unbalanced source into a balanced mic pre input, make sure phantom power is turned off and don't turn it on while the gear's connected. There are often DC blocking caps and other protection circuitry to accomodate, but I'm not one that likes to push my luck on that.
     
  3. mark4man

    mark4man Active Member

    stickjam,

    Thanks.

    Found this resource at another board:

    http://www.rane.com/note110.html

    Check out pages 5, 6 & 7...specifically the configuration #13 on page 7. To answer both of our questions (& this seems logical to me, as well)...looks like the unbalanced signal runs fully to the end of the run; & is adapted at the input.

    Thanks again,

    mark4man

    BTW - That's what I originally meant by "2 to 3" or "3 to 2"...not tying those pin #'s together, but rather which end gets adapted.
     
  4. stickjam

    stickjam Guest

    Cool. :cool: I had seen that document before, wished I still had a copy, but couldn't remember where it was from.

    Thanks!

    --Bob
     
  5. vinniesrs

    vinniesrs Active Member

    Balanced vs unbalanced?

    The idea behind the balanced cable is that if any rf or emf interference is induced into the cable, it will be provided an escape route to ground via the shielding, thus protecting your signal.
    You probably know this, but for the sake of the newbies I thought it worthwhile to mention.

    I also wanted to mention that with phantom power as supplied to a microphone, you cannot damage a dynamic mic with phantom power as the voltage is supplied through a pin which is inactive on dynamic mic's.

    99.9% of all dynamics are wired pin2 and 3 with pin 2 + as mentioned in the previous posts. The phantom power is supplied via pin 1. If that pin is not connected to anything on the other end, then the circuit is open, and no current will pass, therefore no damage will result.

    For the sake of convenience I leave the phantom power on all the time. No harm done.

    The biggest thing I would worry about is your gain. You say your current device is -10dbv? Check to make sure that the device it will connect to is also -10 or at least switchable from +4. Most newer product has +4 db line outs. There is a huge difference in gain between the two, so I would just want to do it right. I'm sure you know that gain structure has drastic effects on the quality of the audio.
     
  6. mark4man

    mark4man Active Member

    vinniesrs,

    Thanks.

    That's all true...but (as Bob Katz says), in a single room studio where all cable runs are short & all gear is connected to a central source, unbalanced almost always sounds better (unless the key gear is expressly mfg.'d with well designed balanced stages.)

    That's what happened to me. In this instance, my source was a synth module (which typically sport unbalanced, -10dBV outputs running @ around 1 to 1.3kohms.) The best sounding signal was via 1/4" TS to 1/4" TS right into the DAW (with the nominal inputs set to -10dBV, of course.) But this also only gave me an input level of around -18dBFS. So my solution (after farting around with Z matching Xformers, etc.) was simply 1/4" TS to XLR Male > Preamp > DAW. I could get better S/N Ratios with the Xformers (because of the isolation & step-up aspects)...but the unbalanced still sounded better.

    mark4man
     

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