Connect with us

How do I vanquish the hum monster?

Discussion in 'Electronic Repair' started by William Rossiter, Nov 24, 2003.

Scroll to continue with content
  1. I've installed a 1/4" phono jack that cuts out the 3" TV speaker when I plug
    in the phones. But I get a whole lot of hum in the phones. I am guessing
    that because the phones are more sensitive than the speaker, I have to turn
    the TV volume control down quite a bit, making the hum more audible than the
    program sound. I am further guessing that I could put some kind of
    attenuater into the circuit that goes into the phones, but not into the
    speaker, and thus could turn the volume up to outshout the hum without
    busting my eardrums. But I don't know where to go from there: do I just
    wire a resistor into the hot side of the signal? Or what?
     
  2. James Sweet

    James Sweet Guest

    You want a resistor in series with the headphone jack. Something you should
    check though, if this is a hot chassis set as a great many are, then
    installing a headphone jack is *very* dangerous since the jack will be
    floating more than 120v above ground and is a serious shock hazzard. You
    need to isolate it with a transformer.
     
  3. Jerry G.

    Jerry G. Guest

    On a standard headphone you need a resistor in series with each side of the
    headphones, one for left, and one for right. The value used is usually
    around 120 to 150 ohm at 1 watt for each resistor.

    If your set is not isolated from the mains this can be a very dangerous
    ordeal, and present a safety hazard. A headphone should only be connected
    to a unit that is isolated from the AC mains. Most consumer equipment is HOT
    to the AC mains on its speaker drive.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    I've installed a 1/4" phono jack that cuts out the 3" TV speaker when I plug
    in the phones. But I get a whole lot of hum in the phones. I am guessing
    that because the phones are more sensitive than the speaker, I have to turn
    the TV volume control down quite a bit, making the hum more audible than the
    program sound. I am further guessing that I could put some kind of
    attenuater into the circuit that goes into the phones, but not into the
    speaker, and thus could turn the volume up to outshout the hum without
    busting my eardrums. But I don't know where to go from there: do I just
    wire a resistor into the hot side of the signal? Or what?
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-