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Hum eliminator for a Laptop

Discussion in 'Recording' started by crxcte, Sep 2, 2003.

  1. crxcte

    crxcte Guest

    I bought a laptop to do some recording and the noise was terrible. All I'm using is live recording from a mic (no MIDI). I've seen the advertisement on the EBTECH hum eliminator and it says to locate the eliminator between the problem equipment. I'm only using a mic so I assume the noise is inside the laptop. Any ideas how to resolve this issue? I bought the laptop (Toshiba) for recording. Should I of bought a Apple laptop instead?

    Thanks in advance,

  2. falkon2

    falkon2 Well-Known Member

    As a general rule, laptops have integrated sound cards which may or may not sit right next to noisy components like the processor and hard disk. Also, since space is an issue with laptops, more often than not all the bells and whistles are trimmed off the components - Laptop recording via the integrated sound card sounds horrible regardless of whether the hum is there - I don't even want to think what kind of bit depth and sample rate my one is going at - add to that the fact that there's constant hum at maybe -30dB on the right channel, and you'll know I'll be a happy, happy falkon2 when I finally get my audio interface. ;)

    Get ahold of a USB or Firewire audio interface - M-audio makes a few good ones that are decently priced.

    However, in the meantime, a quick fix that I use to get mediocre sounding recordings (still scratchy and muddy, but at least without the hum) is to record a sample of the hum without anything else, then invert polarity and mix it back into the recorded track. At the correct phase, the hum cancels out.

    (Signal + hum) + (-hum) = signal

    Quality still sucks, though.
  3. AudioGaff

    AudioGaff Well-Known Member

    Hum should not really be a problem with any laptop made in the last 5-years. A few basic things. Make sure you keep the mic and cable away from the LCD screen and the power cable/transformer. Check you connections and wiggle them a little. This hum may be a bad or loose/flakey connection.

    Are you sure that you have the right cable and/or connectors?
    Are you sure that mic and cable you are using are problem free?
    Have the mic and cable been verifed to work problem free somewhere else?
  4. realdynamix

    realdynamix Well-Known Member

    :) Laptops and their mini jacks, unpredictable input level matching, impedance, and lousy sound cards are terrible for recording as is.

    If you want better sound, use an external audio interface (PCMCIA or USB) to connect your audio I/O's. The EB Tech won't help because it is an in line device. The external interface should eliminate all your noise problems, and allow you to use XLR mic connections too, depending on which interface you choose.

  5. falkon2

    falkon2 Well-Known Member

    AudioGaff: Hmm, AFAIK LCDs are practically noiseless compared to the processor and HD chugging. Do you have any experience otherwise? Might start having to watch out for these in future, though I know my own laptop has practically no humming caused by LCD

    CRT on the other hand... ug.
  6. AudioGaff

    AudioGaff Well-Known Member

    True, LCD's are less problem than CRT's. I always try to avoid having any audio signals near things that may induce noise. LCD's can be a problem as well as HD's, poor or faulty cables as a problem for static and noise being picked up. These in combo with other laptop related RF noise/interference issues can often times be a problem. I never noted any serious problem with a LCD and a mic, but I have with a guitar, many times.
  7. crxcte

    crxcte Guest

    Thanks for the input. I record off a desk top also using the same mic (not using MIDI) and the noise doesn't exist. I'll check out the USB. I guess wrapping the laptop in aluminum foil would make for more isolation tests during recordings.

    I don't see how the FCC lets these manufacturers off the hook on allowing internal noise. Your vacuum cleaner is tested not to affect the TV, laptops internal components should follow the same tests.

    Thanks again,

  8. falkon2

    falkon2 Well-Known Member

    I don't think the foil would help much in any case. ;)

    Recording on something as compacted as a laptop introduces noise inside the box itself - when the signal is passing through the sound card components.

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