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line noise / interference from power lines etc?

Discussion in 'Electronic Basics' started by [email protected], Sep 10, 2007.

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  1. Guest

    I'm trying to record cassettes and LPs to my PC and am experiencing
    line noise, possibly from some other device in the house. I have not
    determined the source of this noise, but it occurs at random times
    during the day, and causes clicks and pops that ruin any recordings. I
    have tried moving the computer & audio equipment from the basemeent to
    different rooms in the house and still am hearing noise.

    The equipment being used is

    * System: Pentium 4 PC running Windows XP Pro
    * Software: Sound Forge
    * Audio Interface: Tascam US-428
    * Cassette deck
    * Turntable (with preamp)

    I have used most of this equipment for a long time and not had
    problems with noise like this in other houses/apartments, and I've
    only noticed noise like this in this house in the past couple of
    months (then again I haven't tried transferring LPs or cassettes in
    this house, however I have recorded guitar/drums/etc here for a couple
    of years and not experienced this kind of noise).

    A recording of the noise and images of the waveforms can be heard &
    seen here:
    http://www.geocities.com/usenet_daughter/line_noise.htm

    Can someone tell what device in the house might be causing this (the
    house has all the normal amenities - lights, A/C, W/D, etc.) or how to
    filter this noise out of the signal loop before it reaches the
    recordings?

    Much appreciated!
     
  2. The time scale of your images is so long that the interference only
    appears to be 1-pixel-wide blips on the timeline. Analysis of the
    waveform would require significant zooming in on an individual
    spike.

    OTOH, at first glance, they look something like the interference
    we see from GSM cell-phones. It typically sounds something
    like: brrrrrup--brrrrrup--brrrrrrup. It is particularly noxious in
    wireless microphone systems, but I've seen it get into other
    low-level audio circuits (such as from a phono cartridge, etc.).

    There has been much discussion of GSM and other cell
    phone interference over on the film sound newsgroup:

    Note also: http://en.wikipedia.org/wiki/Gsm
    "It is a common occurence for a nearby GSM handset to induce a "dit, dit
    di-dit, dit di-dit, dit di-dit" output on PA's, wireless microphones, home
    stereo systems, televisions, computers, and personal music devices. When
    these audio devices are in the near field of the GSM handset, the radio
    signal is strong enough that the solid state amplifiers in the audio chain
    function act as a detector. The clicking noise itself represents the power
    bursts that carry the TDMA signal. These signals have been known to
    interfere with other electronic devices, such as car stereos and portable
    audio players."
     
  3. Benj

    Benj Guest

    No we can't tell you what in the house is causing this. It might not
    even be in the house. I had severe noise and crap on my house power
    that seemed to be welding machines somewhere in the neighborhood. Even
    though I went out trying to track the noise with a radio I never found
    the source. In your own house you can start shutting down circuits
    and suspected sources and observe it the noise leaves.

    Usually the pole transformer tends to block heavy noise from the rest
    of the neighborhood, (but not always!). So the way you filter out
    line noise is to install a power line noise filter! (duh!) However
    note that many things sold as "line filters" and surge suppressors are
    really non-linear devices soldered across the line to clip spikes.
    They are not very effective though can off a bit of improvement.
    You'll need a "REAL" line filter with Ls and Cs to get rid of the
    noise. You can buy these units. Note however, that the noise MIGHT
    not be getting into your recorder up the power line!!! If the noise
    is on your house wiring, the noise might be TRANSMITTED through the
    air from the wires in the walls to your gear! In that case a power
    line filter won't help. Look into resonate transformer voltage
    regulators as they will also act as great filters. Best would be to
    borrow one and try it before laying out the (big) bread.

    Benj
     
  4. () writes:

    Come on, bozo, you're as bad as the troll "radium".

    Why in the world did this have to be cross-posted to
    rec.audio.pro
    rec.music.makers
    comp.sys.ibm.pc.soundcard.tech
    sci.electronics.basics
    sci.physics.electromag

    Figure out your ability, and post there. Or figure out the
    most appropriate newsgroup, and post there.
    Don't use carpetbomber to "increase" the chance that you'll
    get an answer you like.

    I've yet to see a post of yours that isn't massively cross-posted,
    to highly disparate newsgroups.

    Michael
     
  5. Dave

    Dave Guest

    you missed a couple possible noise sources associated with the computer...
    does it have bluetooth? wifi? wireless internet card?? or did you lay
    your cell phone near the equipment?? sure sounds like some kind of digital
    communications stuff, though it could still be some kind of line noise. i
    have also heard crosstalk within a pc from wired mice that kind of sounded
    like that, you can usually tell these since the noise changes as you move
    the mouse.

    to get rid of it, assuming it is rf and not an internal noise, add a
    ups/line filter. change all audio cables to shielded types. Make sure all
    equipment is powered from the same ups/filter. keep all cords short.
    disconnect speakers if you have separate wired in ones while you do the
    dubbing since their cables are generally long and can pick up noise. try
    unplugging or turning off breakers to other stuff in the house and see if
    the noise goes away. try unplugging other stuff on the computer and see if
    it goes away, even the monitor.
     
  6. Guest


    So *that's* where that "dit di-dit" sound comes from! Thanks! I
    thought my wife's JVC car stereo had a hardware defect. When playing
    CDs (not the radio, even), we'd get that every now and then on an hour-
    long road trip. Not sure if it happened while she was receiving a
    text message, but normally her GSM phone would ring if a text message
    were received.

    Michael
     
  7. In a moving vehicle, most likely as you were handed-off while
    moving from cell to cell.
     
  8. Guest


    My first experiment is see if you can hear it in between stations on
    an AM Radio. Then use the radio as a direction finder.

    Here are a list of things to try:

    http://www.oldtemecula.com/theremin/noise/index.htm

    Good Luck,

    * * *
    Christopher

    Temecula CA.USA
    http://www.oldtemecula.com
     
  9. Havatcha

    Havatcha Guest


    From your recordings, this sounds like impulsive noise. Typical sources
    of impulsive noise are electrical motors or other devices that create
    sparks.
    The following gives an overview...

    http://www.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP080.pdf


    the other possibility is that your neighbour has recently bought a
    Power-Line home network kit and is currently spurting RF noise in every
    direction.

    http://www.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP116.pdf
     
  10. Mikey

    Mikey Guest

    Refrigerator? Freezer? A/C?

    Mikey Wozniak
    Nova Music Productions
    This sig is haiku
     
  11. Havatcha

    Havatcha Guest

    Possible, but the pulses sounded a bit too frequent to be switches from
    those devices.
     
  12. Mark

    Mark Guest

    do the noise pulses occur at the SAME TIME in both the left and the
    right?

    in one case it sounded like no.

    It is hard to imagine any EMI creating noise at different times in
    the L and R.

    Mark
     
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