Help needed..ground pin on trrs 1/8" jack

Discussion in 'The Projects Forum' started by Stephen Flynn, Oct 12, 2015.

  1. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    Hi, hoping someone help identify the ground pin on this jack. I checked continuity and from the tip to the end it goes 4321 1234, but unabled find datasheet or correct name for this jack that came out a cheap chinese pair headphones. These are generally potted in some kind of black rubberised substance. If anyone can tell me how to identify ground with my DMM, that would be appreciated. I have googled and there sppear to be multiple ways..but 3 is ground. Can anyone confirm?
    Cheers
    Steve
     
  2. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    Oh yeah i plan to use this to make a I-rig style interface to play guitar through the audio port of my macbook. My plan for this jack would be to insert it in about an inch of drinking straw or pvc tube and pot it again once soldered using hot glue;)
     
  3. #12

    Expert

    Nov 30, 2010
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    The shank is always the ground. You have called it pin 1.
     
  4. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    Ok will try pin 1. I will solder and hook it with alligator clips until I get noise from the circuit. cheers
     
    Last edited: Oct 12, 2015
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Does it have a microphone? Note the Nokia is different than the Apple (standard) iphone - note ground pin on 4 segment (w/ microphone).


    image.jpg
     
  6. Stephen Flynn

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    Sep 29, 2015
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  7. GopherT

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    Measure resistance of tip to first ring. You should see 30 to 100 ohms. Then measure resistance from tip to the second ring - either half of the first measurement or very high. If half, third is your ground

    Next measure tip to sleeve. Either high or 1/2 of first measurement. If half of first measurement, then sleeve is ground.
     
  8. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    ok wonder if it's the same on a macbook as iPhone...confused!! the circuit is supposed to get powered by 2.8v that macs put out through mic pin..maybe I can't just use any jack i scavenged from broken headphones... I just put the empty jack into the audio input of my macbook. Set the audio port for sound input. I then tried putting my ground lead of my DMM on each of the 4 pins and probed the other 3...numerous times.. no sign of the 2.8v???? Thought it would be the way to find ground and the mic pin..that's all i needed to know. Should I not see that voltage???hmmmmm
     
  9. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    OK trying that now
     
  10. GopherT

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    Nov 23, 2012
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    Wait! Your cable is clipped from the connector. At this point it does not matter what WAS ground, everything is cut. You can define the function of each pin as you want.

    The only way you will see 30 to 100 ohms from tip to first ring is if you have the two headphone speakers connected.
     
  11. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    I dunno..i had to set my DMM to 2M setting..and some remittances were above..wildy fluctuating.. tested on sub 1k resistors and the DMM is working..don't know. If I try on the 200, 2k, 200k settings on my meter..I get 1s... not till i set the range to 2M do I get readings????

    Theres a pattern generally 320k - tip ring1, 600k tip - ring2, tip-sleeve- off the charts??? double checked on some resistors..working fine..
     
  12. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    now you tell me :) lol
     
  13. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    do you know why i'm not seeing a voltage on any pin when i plug the unpopulated jack into the audio port?? I tried every pin as ground and checked all other pins for voltage..every combo possible..nothing??
     
  14. GopherT

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    Nov 23, 2012
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    You might see something if you set the meter to V (AC). mV if you have it.
     
  15. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    just tested the jack in my iPad and a I got 2.7v when I have red probe on pin 1, and COM on 2,3 or 4. Tried AC also on macbook nothing. Had never tried it before but I just plugged in a set of headphone with built in mic, samsung brand..it works fine on macbook?? tested the mic in garageband..works ok.
     
  16. #12

    Expert

    Nov 30, 2010
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    Apple? They always try not to follow the standards. :rolleyes:
    ps, I called it the shank, but most people call it the sleeve. It's almost always ground because the jack it plugs into usually has a metal mounting nut which makes the area farthest from the tip become connected to the box it's attached to. If the box is metal, it's automatically ground on the nut.
     
  17. Stephen Flynn

    Thread Starter New Member

    Sep 29, 2015
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    I'm going to take a punt and say that this jacks pinout are 1left, 2right, 3 ground, 4 mic ...which seems to be the way iPhones/ipads are set. And the jack required for the macbook which is 2011 model, has the standard 3mic, 4 shaft/sleeve. Anyways I've wasted enough of everyones time on this. Alls I'm trying to do is make a little rig to test out my real project - charge amplifier preamp for piezo pickups on an acoustic guitar. I just want to be able to direct record on my macbook and view the waveforms using the frequency analyser in Garageband which excellent, for newbs who have no access to, or know how to use a scope:) The cutdown version of GB on the ipad has nothing useful, so I needs find a jack that will work on the Macbook. Tested this gizmo on the iPad..sounds "tinny"..too much high end, probably because the schematic I used has a low pass filter set well above the low note for acoustic guitar, on input then and filter on the output that seems to attenuate everything above 7k - must be an electric guitar thing??. Its undone all the good work of my charge amp preamp..I think I might have an attempt at changing the lowpass RC filter to lower it, and see what effect that has.
     
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