What is the peak to peak voltage on RCA audio sockets on TV receivers?

Discussion in 'General Electronics Chat' started by cumesoftware, Apr 29, 2008.

  1. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
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    Hello.

    I need to know the peak to peak voltage of the audio signal comming from an RCA plug that can be found on the back or on the side of modern TV sets. Is it the same voltage as the one found on a stereo headphone socket (Vpp = 775mV, I think)?

    My DVD has two RCA plugs for sound and one for video. I connected the headphones to the sound plugs and magaged to hear perfectly. My DVD had thge volume turned on full, but it didn't seemed that loud. I think the singal comming from a TRS socket is tipically louder on the same conditions (full volume).
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    The somewhat loose spec for 0 dB audio level is 1.24 VRMS. Multiply by 1.404 for peak. Line audio signals should be close to that level.
     
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    The headphone jack is designed to drive relatively low impedance headphones, whereas the line-out from the DVD is for a relatively high impedance input amp.

    The spec for 0dBu is 775mV RMS, and is becoming typical for line-out from VCR's, DVD's, etc.

    You shouldn't try to plug headphones into a line-out, they are not made for that.
     
  4. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
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    Ups! I didn't knew. Thanks!

    I think someone mentioned something close to 775mVpp for stereo jacks (I think it was 375mVp). I read the value of 775mV in a book about HiFi amps, but it was not mentioned if the value was RMS, so I assumed it to be Vpp. Nevertheless, I'm planning to make an amplifier that uses RCA inputs instead of jack inputs.

    One more question: For RCA outputs, is the signal balanced (is pure AC), or do I have to expect a Vpp equal to Vp (as it happens with positive biased signals such as the ones found in jack outputs)?
     
  5. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    As I recall, RCA plugs/jacks are more commonly known as phono plugs/jacks (not to be confused with phone plugs/jacks such as for headphones).

    As a designer you should never allow any significant DC offset on an audio output, which is why single-supply designs require DC-blocking output capacitors. However this is also why input capacitors are used, because you can never be sure of what someone else may, or may not, do.
     
  6. Norfindel

    Active Member

    Mar 6, 2008
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    The output signal should not have any DC component, it should swing positive and negative from gnd. You can measure this with a voltmeter in DC, it should read 0 with the output in silence.
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    As I recall, if it doesn't specify pk or pk-pk, the values listed are rms.
     
  8. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
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    Thanks! Exacly the answer I was looking for.
     
  9. Norfindel

    Active Member

    Mar 6, 2008
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    You're welcome.
    I'm curious, what are you going to do with the line out?
     
  10. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
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    I'm planning to do an amplifier with integrated speakers, a powerfull one. It will have 2x8W for the satellites plus 16W for the central woofer. But those are only estimated values.
     
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