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Headphone jack install in turntable

Discussion in 'General Electronics Discussion' started by Kroensburg, Jul 13, 2010.

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  1. Kroensburg

    Kroensburg

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    Jul 13, 2010
    I bought a Crosley CR249 Keepsake USB Turntable a little while ago and I love it. The cabinet is all self contained; it has speakers built in. A major downside is that it doesn't have a headphone jack. I'm interested in installing one but I'm not too knowledgeable about circuits or anything. I have a basic knowledge and I can read a schematic fairly well, and I know how to solder, so if anyone can help me out, I'd love it. I figured I could just install a headphone jack that would bypass the speakers when it was plugged in, but I don't know how exactly to go about doing that (where to attach it in the circuit, what resistors I'd need to use, etc.) If you need pictures or anything, I can get them up here, too. Again, I would love any help I can get.
     
    Last edited: Jul 13, 2010
  2. Kroensburg

    Kroensburg

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    Jul 13, 2010
    More information: the power consumption of the whole device is 12 watts. There are two speakers, each of which says 3 watts and 8 Ω. I thought they may be some useful information...
     
  3. Resqueline

    Resqueline

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    Jul 31, 2009
    One criteria for being able to do this is that both speaker outputs have a common ground.
    You'll need a stereo jack socket with internal switches (thereby having 5 connections). I don't think you'll need any resistors since the unit is so low-powered.
    You just cut the wires going to the speakers and insert the jack there. If you connect it the wrong way around you just won't get sound in the headphones, only speakers.
    What kind of headphones do you intend to use btw.?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I presume it's stereo.

    If you have a close look at a stereo headphone jack you'll notice that it has quite a number of connections.

    One of these is the common ground connection, 2 are for the left and right signal, and another 2 are connected to the left and right signal until the jack is plugged in.

    The simplest (although not the best) approach is to connect the speakers via the headphone jack such that they are disconnected when the headphones are plugged in.

    You will have to make sure the volume is turned down when you plug the headphones in or you will blow the headphones up (or possibly your head off). Just kidding -- it could be *very loud* and it could damage the headphones or your ears.

    A better way is to tap into the signal after the volume control, but before the power amplifier, but it may not be trivial to find a place that is both accessible and has a suitable signal level.

    edit: serves me right for waiting an hour to respond :)
     
  5. Kroensburg

    Kroensburg

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    Jul 13, 2010
    Thank you both very much for your help. I can't imagine it would but does it matter if I use a 1/4" vs a 1/8" jack? It's a retro-looking turntable so I wanted to stay in line with that and 1/4" seemed more 60s/70s than 1/8" (maybe I'm just making that up, though...) Also, like I said, I'm fairly new to this whole game; would the jack come with a diagram as to what should be hooked up where or is it pretty self explanatory?
     
  6. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    Size doesn't matter here, or if it does it'll be easier to find a 1/4" jack with switches.
    I never noticed any diagrams or labels on (or with) those jacks so you may have to measure or try it out. If they happen to be an open design the workings'll show by itself.
     
  7. Kroensburg

    Kroensburg

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    Jul 13, 2010
    Ok, so I pulled this headphone jack out of an old stereo (who plays CDs these days anyway?) and was fairly easily able to establish which connections did what, as I mapped out in the attachment 1.

    The two speaker disconnects (I don't know the technical term for it) are in contact, but when a headphone plug is inserted, one of the pair on each side has a lever, so it disconnects from its complementary connection, thereby cutting the signal to the speaker.

    My question with that is: does it matter which one I have coming from the circuit board and which one I have going to the speaker when I connect the wires? I can't imagine it would since they don't touch any other part but themselves.

    Also, since the speakers' wires need to be attached there, do I need to route another wire to attach to the ring and tip connections? (attachment 2)
     

    Attached Files:

  8. Kroensburg

    Kroensburg

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    Jul 13, 2010
    I think I've figured it out but I just wanted to get some last bits of advice before I try it out and potentially kill my record player. If one (or a couple) of you could look at my makeshift diagram and tell me if I have it right or not, that'd be excellent and I'd be eternally grateful.
     

    Attached Files:

  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,419
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    Jan 21, 2010
    I can't be 100% certain, but it looks right.

    Just check that you have left and right the correct way around for the headphones.
     
  10. Kroensburg

    Kroensburg

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    Jul 13, 2010
    Thanks. I know I have the right and left correct. I actually just got it working with the headphones by only connecting the tip ring and sleeve just to make sure that worked. I just wasn't sure whether I was doing it right adding that second set of wires coming off the circuit board for the headphone output.
     
  11. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    Looks right, if the jack works the way I believe it does. If the headphone volume turns out too loud/sensitive you can add resistors in series with the "inner" red (ring/tip) wires.
    It won't kill it if you got something wrong, unless maybe if you crank up the volume to full blast.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    you don't need to use a second set of wires coming from the circuit board to the socket, but it won't hurt anything.

    If you find that the volume is relatively loud in the headphones as compared with the speakers (i.e. you have to turn the volume down a long way so you don't blast your eardrums) then you could insert a resistor in series with the ring and tip connections. Values between 10 and 100 ohms are probably in the range you'd want (it all depends on the impedance of the headphones, their sensitivity, the actual power output of the amplifier, etc, etc.)
     
  13. bostonrob

    bostonrob

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    Jul 16, 2010
    I'm actually trying to do the same thing, just wondering Kroensburg how you got the turntable open? I've have a heck of a time trying to get it open but don't want to break anything.
     
  14. Kroensburg

    Kroensburg

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    Jul 13, 2010
    bostonrob, if you've got a Crosley like mine, it's really easy (although I ran into troubles too). It's just the four screws on top. It's wedged in there kinda good because of the vinyl covering, but I took that big screw next to the platter (the one that allows it to float on springs) and tightened it all the way down and used that as a handle to pull the whole top section off. If you have something other than this or a similar Crosley, I don't know what to tell you...
     
  15. bostonrob

    bostonrob

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    Jul 16, 2010
    Yeah I have a Crosley as well, I took the screws out and will try it again.
     
  16. Kroensburg

    Kroensburg

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    Jul 13, 2010
    Yeah, I had a little trouble at first, but I eventually figured it. Once the 4 screws on top are out, the top will lift straight out.
     
  17. bostonrob

    bostonrob

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    Jul 16, 2010
    Alright I got it open, now what the heck do I do! lol Very new to this, any helpful info besides what's already posted is much appreciated thanks guys!
     
  18. Kroensburg

    Kroensburg

    9
    0
    Jul 13, 2010
    Yeah, I didn't really have any knowledge either. I don't know what to say other than what's already been said. Just solder the wires so the speakers run through, but when the headphones are plugged in, it cuts the speakers and the signal runs through the headphones.
     
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