A tip for those of you who throw parties..

all of my experimenting with XLR matching transformers is not completely wasted. I did figure out this one really neat trick which has elimited the annoying hum and computer noise in my computer speakers.

(I should mention that my computer speakers are a pair of Mackie SRM450s with balanced inputs, and that most of this does not apply to you normal consumer-type people)

Take two XLR -> 1/4″ matching transformers (currently $15 at a guitar center near you), plug them into each other using a 1/4″ F-F adapter ($4), and add a XLR male-male to one of them ($8). Now what you have is a single-channel isolation transformer! Perfect for when you have to run the PA off four different wall sockets in order to get enough power to avoid opening breakers when you start feelin’ the bass. Add heatshrink to the transformer -> F-F -> transformer part, and you have a very useful generic adapter to keep in your adapter kit. Probably a good idea to keep two or three of them around.

Also, when running Mackies off unbalanced outputs that may have less than perfect grounds, a single isolation transformer plugged into a RCA-m->1/4″-f adapter (assuming you’re dealing with a RCA out) will improve the situation mightily. Very useful for ‘booth’ speakers when the power supply is noisy (and, at raves-^H^H^H^H^Hparties, they always are).

6 Responses to “A tip for those of you who throw parties..”

  1. anonymous Says:

    Just use those infamous “nev’R’trip” Federal Pacific Electric breakers and you won’t have a problem with opening breakers.

    I think that’s how my last employer managed to overload a wall outlet to the point where the UPS plug (which was a 30-amp plug, chopped off and replaced with a 15-amp one) caught fire and burned up.

    Amazing, too, because just a couple weeks earlier I got into a major fight with one of my co-workers about whether it was a good idea to put anymore servers on that UPS.

    I only wish I could’ve been there to see it burn.

  2. ClintJCL Says:

    There’s always optical digital audio out.

  3. ClintJCL Says:

    I was also recently pleased to learn that HDMI cables use XLR ideas, i.e. same signal twice, but once inverted, to get their video from point a to point b.

  4. ClintJCL Says:

    Oh also I have two of these things called “ground loop buzz isolation transformers”, i have one on the output of my computer (50 ft rca cable run to upstairs), and another one i used to use either for incoming video capture audio, or for vcr-to-vcr copy, back when i did that.

    For $15, it was great for me, with no actual ability in actual electronics (but an understanding of how to put things together), to be able to eliminate 90%+ of the hum in one fell sweep. It was like a magic silver bullet.

  5. sheer_panic Says:

    Yah.. but most of us use Mackie or JBL active systems that don’t have digital inputs. It actually doesn’t even need to be optical.. a little 100mV AC hum never bothered a 1V-swing digital signal.. but the people who make the speakers haven’t gotten there yet.

  6. sheer_panic Says:

    It’s not suprising.. some router backplanes use balanced systems.

    What I’m describing here is how to build a ground loop isolater for far less than the ‘real’ ones cost for XLR…

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