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HELP: headphone/TV RCA connection

Discussion in 'Electronic Basics' started by [email protected], May 1, 2006.

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  1. Guest

    I have a pair of normal (unpowered) stereo headphones that I would like
    to connect to my rear projection TV without using a stereo receiver in
    between them. Since I can't see any headphone jack, it appears that my
    only option is to plug into one of the pairs of RCA jacks provided for
    output to a stereo receiver.

    ** How do I make a proper connection between these two connectors?
    Will the adapter off the shelf from some big name comsumer electronics
    store be the right thing?

    Since there's no way to only mute the TV's built-in speakers, if I had
    the choice (i.e., something off the shelf won't work), I would like the
    volume in the headphones to be noticeably louder than the apparent TV
    speaker volume under typical listening conditions. Perhaps the
    "adapter" could include a volume control.

    My TV is a Sony KP-57WS510. The TV OUT RCA jacks are: 500 mVrms, 1
    kiloohm impedance

    My headphones are Sennheiser HD 535's (older version of the 555's).
    They are dynamic/open with a 120 ohm impedance and a sound pressure
    level(1 kHz, 1 Vrms) rating of 103 dB.
     
  2. Guest


    Quick idea:

    Use one of these:
    http://www.headphone.com/products/adaptors-and-accessories/stereo-mini-to-rca-adapter.php

    and use something like this to connect the two male ends?
    http://www.mycableshop.com/sku/251-118.htm
     
  3. Guest

    Ah, yes. I should have been more specific. I know how to physically
    make the connection, but not how to ensure there is an "electrical"
    match between the TV and headphones.

    I'm particularly suspicious of this TV connection, since I've never
    been able to find a resource that can explain why I have to turn my
    stereo receiver all the way up so that there is normal volume coming
    out of my headphones when plugged into the receiver. (I've tried
    setting my TV audio to fixed volume mode--no difference; standard 75?
    ohm cable).
     
  4. mc

    mc Guest

    If they do not output headphone-level signals, you need an amplifier.
    That's what amplifiers are for; that's why they are manufactured.
     
  5. Guest

    The operative word is "if." That's why I wrote my post.
     
  6. mc

    mc Guest

    Right... RCA jacks normally output line-level audio, not headphone-level.
     
  7. Pooh Bear

    Pooh Bear Guest

    RCA output with a 1kohm source impedance aren't going to drive headphones very
    adequately.

    Graham
     
  8. Don Taylor

    Don Taylor Guest

    Depending on how aggressive you want to get about this, you may
    have another option. (Decades ago when they started cost cutting
    there was something called "hot chassis", which was where some parts
    of TVs of that era might have 115 volts present on metal parts
    inside, to save the price of a transformer. That presented some
    risk if you were going to get into modifying those and didn't know
    what you were doing.

    But I don't think there have been hot chassis in a long long time.
    It looks a lot more common for most of a tv chassis to be one or
    two tiny circuit boards, a few chips, and more likely to run on 5
    or 12 volts than 115.

    So, considering that safety issue, it may be possible for you to
    turn off the set, let it gradually discharge for a while, open the
    case, splice into the wire from the chassis to the speakers, find
    or drill a small hole in a convenient place on the plastic case,
    mount yourself a little jack and create an external headphone jack.

    That is just an option, or maybe not, depending on your skill,
    experience, and willingness to consider this before you decide
    whether or not to do this. (I got a new TV years ago that seemed
    a little to cheap. It turned out to be the end of the line with
    sets that don't have all the various new connectors and features
    out the back. But now it has a headphone jack in the side of it)

    Don't get yourself into trouble.
     
  9. Ban

    Ban Guest

    Usually you need a maximum power of 50 to 100mW for a decent level in the
    headphones. Most headphones are 32 Ohms today, so when yours really have
    120, the normal O/P would give you only a low output. Try to wire the phones
    directly to a spare normal speaker terminal of your stereo with a resistor
    of 470 ohms/1W in series, so they have some protection. Very often the
    volume of the TV is limited by the satellite receiver, which has sometimes
    its own volume control on the remote. Check that also out.
     
  10. Guest

    The last three responses had the kind of info I was looking for.
    Thanks! It seems like I need to find a pre-made (or schematic) for a
    headphone amplifier (w/ volume control) that uses RCA jacks as its
    input.
     
  11. Jasen Betts

    Jasen Betts Guest


    you need a headphone amplifier.

    the sterio outputs will probably not be effected by the TV's Volume setting.
    (so you can turn the TV volume right down and use the headphone amp to adjust
    the sound level for comfort)
    you could try without the amp.. just a RCA to headphone adaptor.
    at 120 ohms they may work acceptably at line levels... still if you're
    buying Sennheiser phones it'd probably not be acceptable.

    Bye.
    Jasen
     
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