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Mackie 1202-vlz causing extreme noise?

Discussion in 'Recording' started by sampsoniter, Nov 23, 2004.

  1. sampsoniter

    sampsoniter Guest

    ok, I have just recently aquired a Mackie vlz micro series mixer from a friend of mine who it works fine for.......and he's was running it to a to an old sb16 card recording in 16bit 44khz with an AT4045 I think.............I'm running it to a sb audigy 2 platinum with an AT3035 mic. recording at 24bits 96khz............I have checked ever connection and even tried other connections yet as soon as I go to record in Acid, I can already tell there is mad noise going on, with the meters jumping.......and when I record anything it's garbage, wityh huge humming/buzzing noise?

    can anyone please tell me
    what's the problem?

  2. JoeH

    JoeH Distinguished Member

    Jun 22, 2004
    Philadelphia, PA/ Greenville, DE
    Home Page:
    I've used Mackie boards into SB Audigy2 sound cards without a problem, but I don't have enough info to REALLY diagnose your problem yet....

    A quick guess might be that you're running your Mixer output into your mic input, or something similar. (those buggers are tiny, and easy to misread on PC sound cards.)

    Do you have the right adapters, (XLR or 1/4" to 1/8", balanced to unbalanced) and/or do you have the input levels set properly for the Audigy? The 1202 VLZ should have a small switch on the back next to/for the balanced outputs, and it's used to set it at mic or line level. If you're using those outs, check there, too.

    Mainly, make sure you're using the correct balanced to unbalanced connectors, esp if you're going out of the main outs to a sound card LINE input like the SBs.

    Another thought is: Make sure all playback inputs are OFF on the mixer, or at least not routed back into the sound card during record (if you're routing your sound card back through the Mackie for monitoring.) It also sounds like you could be setting up a nasty feedback loop if your soundcard is set to "playback while recording".

    good luck!
  3. gnarr

    gnarr Guest

    it sounds to me that the PSU in the mixer is "leaking" AC into your mixer.

    like you probably know electicity is in so called AC form in your walls. this "kind" of electicity has either 50hz or 60hz Phase depending on your eletricity system.

    what the PSU of the mixer is supposed to do is removing those phases, so they won't be in your mix. this is done by sending the current through a condenser (not a condencer mic.. but condencer mics use a "moving condencer" technology) that removes the waves.

    Your problem is probably that those condencers in the PSU of the mixer are damaged in some way and letting the hz's through and into your mix.

    the problem could also be that you're connecting the mixer to a un grounded power source. but it doesn't sound like that to me.
  4. JoeH

    JoeH Distinguished Member

    Jun 22, 2004
    Philadelphia, PA/ Greenville, DE
    Home Page:
    gnarr, that's possible, but I kind've doubt it if the mixer works OK otherwise.......Yes, AC Hum can and does get into the output signal at times if there's a problem with the power supply.

    To clarify things a bit....

    Virtually all present day electronic devices work on DC current. What comes out of the walls is AC current, be it 50 or 60 HZ, depending on locale, country of origin, etc.

    Power supplies (both onboard and wall warts) turn this AC current into DC, by doing several things: stepping down the 120 voltage to something lower via a transformer (9v, 12v, 48v etc.) and running the AC current through a Bridge Rectifier - an arrangement of four diodes that pass this alternating current in only one direction resulting, in most cases, postive voltage over ground/neutral. (Unless it's a bi-polar power supply, etc.) The DC voltage at this point is still noisy and not quite usable, which is where the filter caps come in. (removes the last bit of ripple, hum, etc.)

    I tend to doubt the power supply on his mixer is the cuplrit if it's working OK in every other respect. (Headphone amps, output to other devices, like speakers, etc.) Ditto for the LED light functions, solo light, etc. Things would probably be pretty weird elsewhere in the signal chain.

    I know the above descrition of a power supply is fairly basic, but it might explain things a little bit more; failed bridge-rectifiers (diodes) are just as likely a cause of MAJOR AC hum and system failure. It's not always the fault of the CAPs.

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