How to get a "line out"

Discussion in 'iPod' started by MattG, Oct 17, 2007.

  1. macrumors 68040

    MattG

    Joined:
    May 27, 2003
    Location:
    Fletcher, NC
    #1
    I'm trying get a line out from my iPod -- that is, just a signal to send to an amp, without the gain added by the headphone jack. What's the best way of achieving this? Do I need the dock, or is there just a special cable or something, etc.? This is for a 160gb Classic.
     
  2. Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #2
    I think, FWIW, you have it backwards. Line out is amplified in comparison to headphone signals. That's why, when you use the headphone line into a receiver, amp, etc, you have to turn it up much farther than you would otherwise.

    A dock is probably the most expedient way, as you can also use it to let the iPod stay charged and run off wall power. Sendstation makes another option if size or portability are concerns.

    [​IMG]

    EDIT: You probably want the USB version, sorry, but same idea.
     
  3. macrumors Core

    Joined:
    Jun 16, 2004
    #3
    Line out is the lower of the two.
    Line level goes to the headphone amp.
     
  4. thread starter macrumors 68040

    MattG

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    May 27, 2003
    Location:
    Fletcher, NC
  5. Moderator emeritus

    mkrishnan

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    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #5
    Sorry, I guess I should have been more clear. A headphone amp for studio headphones (that need relatively a lot of power) takes line level input and outputs a level of power suitable to the headphones. But the typical output of a headphone / earphone jack on a consumer device like an iPod is weaker than line level, isn't it?
     
  6. macrumors Core

    Joined:
    Jun 16, 2004
    #6
    There's not a huge amount in it, to be honest, but running an iPod from the headphone socket to the line in of another amp can overdrive the input stage and lead to distortion.
     
  7. Moderator emeritus

    Joined:
    Jul 4, 2004
    #7
    No, but because of impedance mis-matches, if you plug the headphone output into a line-in, you're going to get noise, attenuation and treble roll-off.

    Headphone out = usually milli-watts into 16-32 ohms, line-in = 600-2000 ohms at 0.7 volts (I think).

    Plug some headphones into a line-out and you're going to hear very little.
     
  8. macrumors 68020

    Joined:
    Jan 7, 2003
    Location:
    Washington, DC
    #8
    Sik makes something similar.
     
  9. macrumors Core

    Joined:
    Jun 16, 2004
    #9
    Do you know everything?:)
     
  10. Moderator emeritus

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    Jul 4, 2004
    #10
    Oh yes... ;)

    Nah, just some random neurons firing their last sparks from a previous life of running a little studio at school. Me and my TEAC 4-track; good times.
     
  11. Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #11
    Hmm... I guess that makes sense, although you're mixing your units. :p

    It does work reasonably well the other way around -- you can't plug headphones into a line out, but you can plug a headphone out signal into a line in. Typically if you output at 75-85% of the device max output (but not 100% for some devices, particularly the iPod), and you increase the gain on the amplifying device slightly (maybe 20%-30% more than normal) you get reasonably clean amplification, given all the limits involved. In a crucial application though, certainly you want a device that gets the iPod's line-out signal from the dock connector.
     
  12. Moderator emeritus

    Joined:
    Jul 4, 2004
    #12
    I know. I left it for you to work out the voltage... ;)
     
  13. Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #13
    Thank you, Ms. Velvet. :)
     
  14. macrumors 603

    notjustjay

    Joined:
    Sep 19, 2003
    Location:
    Canada, eh?
    #14
    RMS or P-P? :p
     
  15. Moderator emeritus

    Joined:
    Jul 4, 2004
    #15
    RMS, natch. ;)
     
  16. thread starter macrumors 68040

    MattG

    Joined:
    May 27, 2003
    Location:
    Fletcher, NC
    #16
    Okay so excuse my ignorance but...I just bought a dock. Now I'm listening to my headphones, which are plugged into a headphone amp, which is plugged into the line-out from the dock. The volume control on the iPod still works! I thought the "line-out" would just send a signal. That being said, should I use the line-out with the volume cranked all the way up? I'm confused :confused:
     

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