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Muddle over left/right channel of TRS plug

Discussion in 'Electrical Engineering' started by Peter, Sep 25, 2009.

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  1. Peter

    Peter Guest

    I have a 3.5mm TRS plug which is prewired. It looks like this

    http://www.mycablemart.com/store/images/products/1085_large.jpg

    The tip of that TRS plug is connected to the red wire (RIGHT
    channel).

    Has that been done correctly? I thought the tip of the TRS plug is
    the LEFT channel.

    (I also have a 3.5mm TRS socket which is prewired and the red wire is
    also the tip.)
     
  2. Nope. Tip is left. It has been for 50 years.
     
  3. Does it matter? If it's backwards then just reverse the RCA's?
     
  4. As to colours, in the UK some pro stuff uses red and green
    As far as the RCA plugs are concerned, the Red plug has long been Right.
     
  5. Nope. Tip is left. It has been for 50 years.
    Why do I feel I'm sitting under the caterpillar's mushroom?
     
  6. As a mnemonic, I think of it as a political thing (right=red, left=blue
    [i.e., not-red]).
     
  7. Rich Grise

    Rich Grise Guest

    Does it matter? Can you tell "right" from "left" by ear? Lessee, strings
    on the left, brass on the right, percussion in back...

    Of course if it's wrong, just fire up the ol' soldering iron, and swap
    them. Takes about four minutes.

    Cheers!
    Rich
     
  8. Rich Grise

    Rich Grise Guest

    That's a recent innovation that came with Bush II. Historically, the "Reds"
    have been the commies. ;-)

    Cheers!
    Rich
     
  9. Rich Grise

    Rich Grise Guest

    Is "TRS" a mnemonic for something? All I can think of when I see it is
    the Radio Shack/Tandy TRS-80, pronounced "Trash 80". ;-)

    Thanks,
    Rich
     
  10. Rich Grise

    Rich Grise Guest

    Good drugs? %-}

    Cheers!
    Rich
     
  11. Rich Grise

    Rich Grise Guest

    Oh, yes - the US has been using "Tip & Ring" for about as long as there
    have been telephone exchanges. (a hundred years?) :)

    My cousin Owen inherited Uncle Dick's farm - they still have a
    wall-mounted crank-style phone with the separate earpiece similar to this:
    http://youngandthewireless.com/emptying-nests/wp-content/uploads/2009/05/old_telephone.jpg
    [mind the wrap]
    and they have an early phone book - most of the phone numbers were two
    digits! (Circuit & phone). (it wasn't a very big town. ;-)

    If you're curious, it's Lake Crystal, MN.

    Cheers!
    Rich
     
  12. "jack plug" seems to be a British usage -- elsewhere it is an
    Believe it or not, the OED2 doesn't list this usage.

    Many years ago, when I worked for Bendix Field Engineering, I became
    acquainted with what was known as a "jackscrew" connector. There were male
    and female versions, so I suggested to the manufacturer that they be
    rechristened "johnscrew" and "janescrew" connectors. They had no idea what I
    was talking about.
     
  13. As an aside, wonder how many recordings (commercial ones) are out there
    that have left and right channels reversed. (Obviously not determinable
    on such material as punk rock.)
     
  14. Peter

    Peter Guest

    The wikipedia has a useful entry on TRS (tip-ring-sleeve) connectors.

    Unfortunately the wiki doesn't explain why the left channel on my
    adaptors are connected to a RED wire.
     
  15. Peter

    Peter Guest

    Hi Rich. I would love to just resolder them but the pics show the
    connectors are moulded on to the wires. (That's how we spell
    "molded" here in the UK.)

    It's not for a fixed setup. I'm testing mono microphones but I also
    need to eliminate disparities in the recorder and player.

    Here is are some typical set ups.

    --------------------

    I use a stereo portable recorder and make a recording with one test
    mic on one channel and another test mic on the other channel.


    To compare the two recordings I might do this. Take the L or R (and
    I need to identify which is which because that tells me which mic I
    am listening to) and feed its signal into both L and R conductors on
    the line-in socket on the PC.

    To eliminate disparities created by the recorder (maybe it records
    differently on its L and its R channel) I need to be able to keep
    track of the channels when I switch L and R around.

    An alternative requirement is when I to feed the portable recorder's
    output into the PC on both channels (stereo) and then use I would an
    audio editor to replay either L or R on its own. To avoid colouration
    from the different L and R replay channels of the PC, I connect the
    single played channel so that it comes through both speakers. I have
    to do that by taking the output from the 3.5mm "audio-out" connector
    which is on only one channel and connect it to be on both L PLUS R on
    the input of my powered speakers. I use the adaptors I mention for
    that last step. (In fact it s a bit more comlicted because I also use
    some one-piece RCA phono couplers to spilt out the two channels.

    And there are also other combinations of equipment I use where I need
    to be sure about L and R.

    Phew! Anyway, you can see that mixing up L and R on account strangely
    coloured connectors is going to add points at which errors in
    labelling can creep in.

    I posted because I was wondering if RED = TIP = R-CHANNEL was part of
    some convention I had not heard of which may have made sense if only
    I knew what the convention is.


    --------------------

    I tried to get around any ambiguity from the above by using these two
    components together but their prescence just adds unncessary
    complication because I wire and reqire these combos quite a lot.
    The extra connectors also add more physical connections which may get
    be made 100% and can introduce noise to the audio. (3.5mm connectors
    are prone to this.)

    <http://cpc.farnell.com/pro-signal/psg01989/adaptor-3-5mm-s-to-phono-
    p/dp/AV15537>

    <http://cpc.farnell.com/pro-signal/psg02781/adaptor-2x-phono-to-3-5-
    jack-st/dp/AV17296>


    --------------------

    Maybe those connectors with the RED wired to the tip which I got from
    CPC Farnell are from some incorrectly-wired job lot which they CPC
    were selling off cheap. See links:

    <http://cpc.farnell.com/pro-signal/psg00112/3-5mm-st-plug-to-2x-mono-
    sockets/dp/AV13710>

    <http://cpc.farnell.com/pro-signal/psg00185/lead-3-5mm-s-socket-
    2xphono-2m/dp/AV13783>
     
  16. Peter

    Peter Guest


    I'VE REPOSTED MY MESSAGE WITH FEWER TYPOS!
    IGNORE THE PREVIOUS VERSION.


    Hi Rich. I would love to just resolder the adaptors but my pics show
    the connectors are moulded on to the wires.

    Worse still, it's not for a fixed setup because I'm testing mono
    microphones and need to eliminate disparities in the recorder and
    player. Below are some typical set ups.

    --------------------

    I use a stereo portable recorder and make a recording with one test
    mic on one channel and another mic on the other channel.

    To compare the two recordings I might do this: Take the L or R (and
    I need to identify which is which because of course that tells me
    which mic I am listening to) and feed its signal into both L and R
    conductors on the line-in socket on the PC.

    To eliminate disparities created by the recorder (maybe it records
    differently on its L and its R channel) I need to be able to keep
    track of the channels because I may make another recording with mics
    swapped around.

    An alternative requirement I have is when I to feed the portable
    recorder's output into the PC on both channels (stereo) and then I
    would use an audio editor to replay either L or R channel on its own.
    To avoid colouration from the different L and R replay channels of
    the PC, I connect the single played channel so that it comes through
    both PC speakers. I do that by taking the output from one channel of
    the PC's 3.5mm "audio-out" connector and connect it to both L PLUS R
    of the input of my powered PC speakers. I would use the adaptors
    with the colour problem for that last step.

    In fact it's just a little bit more involved than that because
    sometimes I use a one-piece "RCA phono" coupler to spilt out the two
    channels. I also need some other adaptors as these links show.

    <http://cpc.farnell.com/pro-signal/psg01989/adaptor-3-5mm-s-to-phono-
    p/dp/AV15537>

    <http://cpc.farnell.com/pro-signal/psg02781/adaptor-2x-phono-to-3-5-
    jack-st/dp/AV17296>

    However the presence of all this extra stuff just adds unnecessary
    complication because I wire and rewire these combos quite a lot. The
    extra connectors also add more physical connections which may NOT get
    be made 100% electrically correctly and can introduce noise to the
    audio. Those 3.5mm connectors are all too prone to this.

    There are also other combinations of equipment which need me to be
    sure about L and R. I might work through these combinations every 5
    or 10 minutes depending on the results I am getting.

    Phew! You can see that mixing up L and R on account strangely
    coloured connectors is going to add points at which errors in
    labelling can creep in.

    I posted originally because I was wondering if RED = TIP = R-CHANNEL
    was part of some convention I had not heard of which may have made
    sense if only I knew what the convention is.

    --------------------

    Maybe these connectors I have got are some incorrectly wired rejects
    which are being sold by CPC Farnell. See links:

    <http://cpc.farnell.com/pro-signal/psg00112/3-5mm-st-plug-to-2x-mono-
    sockets/dp/AV13710>

    <http://cpc.farnell.com/pro-signal/psg00185/lead-3-5mm-s-socket-
    2xphono-2m/dp/AV13783>


    Peter
     
  17. Unfortunately the wiki doesn't explain why the left channel
    Careless assembly. I've seen it in other inexpensive adapters.
     
  18. Jamie

    Jamie Guest

    I'm sure the dealer got a deal on them.
     
  19. Rich Grise

    Rich Grise Guest

    When you start your test, tap one mic say, two times, and tap the
    other mic three or four times. (tap as in, with your fingernail.)

    Then see which channel they come out on. :)

    To test the recorder, just use one mic.

    Of course, if the outputs are _also_ swapped, then you'd need more
    experimentation.

    Unfortunately, I don't know if there even _is_ a standard for those
    TRS plugs/jacks.

    Good Luck!
    Rich
     
  20. Peter

    Peter Guest

    Thanks for the info. I wrote that the real problem is the ease and
    speed of channel identification rather than how to use tapping
    procedures to determine which channel is which (and which rely on a
    visual indication of recording levels).

    I think the problem was probably due to some duff batches which CPC
    Farnell were selling off cheaply. I'll check some more of the ones I
    bought and see if they'll swap them for correct ones. The moral must
    be not to trust CPC Farnell's quality assurance.

    Unfortunately the electronic engineering supplier Farnell UK (not CPC
    Farnell) also draws from the same stock for these parts and they say
    this on their website: <<Connectors are an important part of every
    electronic design and Farnell are committed to bringing you the
    latest products from the leading Connector manufacturers>>

    What a cheek!

    http://uk.farnell.com/connectors
     
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