balanced and unbalaced cable ?

Discussion in 'Accessories / Connections' started by mcmilliron, Feb 22, 2005.

  1. mcmilliron

    mcmilliron Guest

    ok I'm confused... help me figure this out.

    signal chain:

    guitar(unbalanced cable)

    Preamp instrument input 1/4 inch (unbalanced)

    Preamp xlr output (balanced)

    ADA Microcab input 1/4 inch (unbalanced)

    microcab output (unbalanced)

    Emu 1212M 1/4 inch input (I can choose a balanced +4 or unbalanced -10)

    can I run the balanced output of the preamp to the unbalanced input on the Microcab without any problems?

  2. MasonMedia

    MasonMedia Guest

    Hello Mark,

    Yes you may connect an balanced out to an unbalanced in. There are 2 ways, depending on the output level. The cable shown below uses 1/2 of the balanced signal, however it assumes the balanced output is not a professional line level (+4dbu). Here the level must be 0 or even -10dbu.

    If the output is line level, and the unbalanced input is -10dbu or even 0dbu, it will overload the input. In this case, a resistive pad should be added to reduce the level, or use a Pro to IHF interface like the MatchBox from Henry Engineering.

    Here's the cable detail for an XLR-3 to unbalanced 1/4":

    Pin 1 Shield to Sleeve of 1/4"
    Pin 2 (+) to Tip of 1/4"
    Pin 3 (-) This wire is not connected (tape over so it does not short).

  3. mcmilliron

    mcmilliron Guest

    I need to find out if the Microcab will except a +4db signal because that is what the preamp puts out. I'm pretty sure the Microcab will except it but I'm not 100% sure, but if it does... will the signal continue to run at +4dbu out of the microcab? or will the microcab convert the signal to -10db?

    this is so confusing... can't they just have one fixed output for all gear!! I guess they have to separate the pro gear from the cheap stuff.

    thanks for the reply

  4. mcmilliron

    mcmilliron Guest

    I just discovered this from The Brick's preamp features list.

    "The Brick will pre-amplify any line or instrument signals directly into a +4 or -10 Line input stage of your mixer or recorder".

    but then it says

    "Line Level Signals Output Level Nominal +4 dBm Maximum +16 dBm terminated at 600 Ohms".

    wouldn't this imply that its fixed to +4 db and should not be run into a -10db input?

    I really want to buy this preamp but I need to know if it will work in my signal chain.

  5. roirat

    roirat Guest

    dBu and dBV

    I've been playing with numbers, and if I got this right, which is by no means certain, that:

    +4dBu = +1.8dBV

    So, if you're connecting the output of a piece of gear that runs at +4 dBu to the input of a piece of gear that likes -10dBV, just back off on the signal (in the first piece of gear) by about 12dB, right? Can anyone confirm this?

    Not too sure how this affects balanced vs. unbalanced. Is balanced assumed to usually be used at a standard of +4dBu and unbalanced at -10dBV?

    I bet someone here is an expert on this and can fully explain.

    (hint: win yourself title of "expert")

  6. mcmilliron

    mcmilliron Guest

    ok check this out... I believe the volume knob on my ADA Microcab will act as a pad if I need to back the level off to my 1212m.

    so does it really matter if its +4db or -10db?
  7. roirat

    roirat Guest

    wait... in my 1212m patchmix (software came with 1212m?) there is a way to choose the sensitivity of the analogs ins, either -10 or +4... find that?

  8. mcmilliron

    mcmilliron Guest

    I think I've got it all figured out.

    thanks for your replies :D

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