Replacing T4F with TRS connector-- Pinout questions

Discussion in 'Microphones & Recording' started by sammichesaretasty, Oct 24, 2013.

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  1. sammichesaretasty

    sammichesaretasty Member

    Oct 24, 2013
    I'm doing a little experiment with live-streaming video from a moving car. I'm looking at using this microphone pin out diagram for the T4F connector[/DLMURL] from shure

    That diagram shows the following:
    Pin1: shield
    Pin2: bias (+5Vdc)
    Pin3: audio
    Pin4: Bias return

    From my research, I've found that the three conductors on TRS connectors are for positive, negative, and drain. What I don't know is how those three would match up to the T4F connector's bias (+5Vdc), audio, and bias return.

    How can I make an appropriate connection given the differences between the number of conductors on T4F versus TRS connectors? There is no place to solder the shield wire on a TRS connector, right? Would the shield wire just not be connected on the TRS end? Is there a better way I haven't considered? Thank you.
  2. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
    Home Page:
    You need a plug-in-power source (5V) for the mic to supply the line marked "bias" on the T4F connector. The Xenyx 302USB has a 1/8" TRS headset mic jack, and it's possible that it can supply plug-in power, but there's no information about it in the user guide. I would try connecting the shield and bias return line to the jack sleeve, the audio to the jack tip and the bias line to jack ring. This is likely to be the correct wiring, but it's by no means certain.

    If that doesn't work, external battery-operated plugin-power sources are fairly easily available, or you might want to go for a phantom power (48V) to plug-in-power converter. We can advise further if needed.
  3. dvdhawk

    dvdhawk Well-Known Member

    Dec 18, 2008
    Western Pennsylvania, USA
    I don't think the PG185 to any 3-conductor connector is ever going to work, sorry. And as far as the mixer goes, when I see the word "Headset" and the mic and headphone jack located together like that, I believe it's looking for a headset/mic like a video gamer or sportscaster might wear. Those kinds of headset mics usually come with a noise-canceling mic, which in a moving car might not be a bad idea. You obviously can't wear headphones while driving, but the noise-canceling mic might be worth trying to adapt. Either worn around your neck or rigged to the visor.

    If you want a broadcast quality lavalier mic and aren't on a Ramen noodle budget, there are wired lavalier mics with full-size XLR connectors that come ready to plug into your XLR. You'd have to decide whether you'd be better served by an omni like the SM93, cardioid model, or super-cardioid model.

    Best of luck.
  4. Lotus7

    Lotus7 Active Member

    Oct 21, 2013
    New Mexico, Illinois & New York
    level control.jpg The PG185 will work fine with an unbalanced (or balanced) mic input if you meet two conditions:

    1. An external +5 to +10 volt bias source is provided (a standard 2U6 9 volt battery is ideal).
    2. A DC return for the impedance converter is provided. Some mic inputs are already DC-coupled and will work "as-is", but many are AC-coupled (capacitively coupled) and won't work unless a 10K to 20K resistor is used across the output. A pot is a good solution to provide the DC return path and also to trim gain.

    In terms of needing a noise canceling mic or not, you will probably have to try it to determine if the noise pick-up of the PG-185 is objectionable or not.

    Schematic attached:

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