Audio pin out needed

Conversations around originating a webcast for conference, including cameras and mixers.
kwillisjr
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Audio pin out needed

Postby kwillisjr » Tue Sep 25, 2012 9:01 am

I think I may have discovered the root cause of our audio hum problem. I see that there was an XLR to 1/8" mini adapter included in the original communicator kit. I'm not sure what happened to it but I've never seen it. We (I) have been trying to adapt from an XLR line level output to what I thought was supposed to be a mono mini line level input. I see now that the adapter is XLR on one end and stereo mini on the other. I'm going to have to make an adapter for our system but I don't know the correct pin out from the XLR to the mini stereo connector. Can somebody enlighten me?
Thanks,
Ken

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rootbeericecream
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Postby rootbeericecream » Tue Sep 25, 2012 4:22 pm

kwillisjr wrote:I think I may have discovered the root cause of our audio hum problem. I see that there was an XLR to 1/8" mini adapter included in the original communicator kit. I'm not sure what happened to it but I've never seen it. We (I) have been trying to adapt from an XLR line level output to what I thought was supposed to be a mono mini line level input. I see now that the adapter is XLR on one end and stereo mini on the other. I'm going to have to make an adapter for our system but I don't know the correct pin out from the XLR to the mini stereo connector. Can somebody enlighten me?
Thanks,
Ken


Radio Shack sells one http://www.radioshack.com/product/index.jsp?productId=2062444#
http://compare.ebay.com/like/330712640904

Also see http://www.coutant.org/matching/5.html for some more info

russellhltn
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Postby russellhltn » Tue Sep 25, 2012 4:29 pm



The items indicated are for 1/4".

One of the reasons I haven't commented on this post is that I'm not sure if the communicator is a "stereo" in or a "mic" in. Both use a "stereo" 1/8" plug. Both are common to PCs.
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kwillisjr
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Technical spec's

Postby kwillisjr » Tue Sep 25, 2012 5:06 pm

Are there no technical specifications available for the communicator? I'm a little surprised that this information is not obtainable.

russellhltn
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Postby russellhltn » Tue Sep 25, 2012 5:49 pm

kwillisjr wrote:Are there no technical specifications available for the communicator? I'm a little surprised that this information is not obtainable.


I can't find anything that goes into that much detail.
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kwillisjr
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I think I have an idea

Postby kwillisjr » Tue Sep 25, 2012 6:05 pm

I did an internet search for information on the pin out of an xlr to stereo mini connector. Given that the output of our building's sound mixer is a balanced mono feed, I think the thing I need to do is connect the audio cable in the sound closet as follows: red - positive, black - negative, drain - ground. On the communicator end I will solder on a stereo 1/8" mini plug in this manner: red - tip and ring, black - sleeve, drain - not connected. I've been using (because it's what was there) a mono mini plug with the red to tip and black to sleeve. The problem here is that the communicator, I believe, is wired internally to accept a 1/8" stereo plug. It's expecting to see the red wire (positive) in the tip and ring positions. Using a mono plug puts the black (negative) wire in the ring position resulting in a conflict between the red and black wires. The installation instructions for the communicator state that a mono plug will not work. The problems I've been having would tend to confirm this.

Wow, what a ride! And I thought this was going to be easy....and quick.

russellhltn
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Postby russellhltn » Tue Sep 25, 2012 6:29 pm

kwillisjr wrote:On the communicator end I will solder on a stereo 1/8" mini plug in this manner: red - tip and ring, black - sleeve, drain - not connected.


That sounds like a good guess, assuming you're using the line-in jack.

kwillisjr wrote:I've been using (because it's what was there) a mono mini plug with the red to tip and black to sleeve.


Normally that wouldn't cause a problem. You might not get audio in one side of a stereo signal, or reduced volume in a mono version. Had the tip and ring been internaly shorted, I don't think you'd get much of any audio at all.

kwillisjr wrote:The installation instructions for the communicator state that a mono plug will not work.


That would expect that to be the case when you use the mic in. The tip is power. The signal is ring and sleeve. But then, if you're connecting a line in to that jack, your going to need an attenuator. Otherwise it will be massive distortion.
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rmrichesjr
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Postby rmrichesjr » Tue Sep 25, 2012 8:28 pm

kwillisjr wrote:I think I may have discovered the root cause of our audio hum problem. I see that there was an XLR to 1/8" mini adapter included in the original communicator kit. I'm not sure what happened to it but I've never seen it. We (I) have been trying to adapt from an XLR line level output to what I thought was supposed to be a mono mini line level input. I see now that the adapter is XLR on one end and stereo mini on the other. I'm going to have to make an adapter for our system but I don't know the correct pin out from the XLR to the mini stereo connector. Can somebody enlighten me?
Thanks,
Ken


Based on other postings in the thread and what I have gathered from my STS, the communicator appears to take stereo line-level input. The feed from the PA system is almost certainly balanced mono. While you could do that conversion with a resistor network (basically by ignoring one side of PA's feed), I would recommend a 1:1 audio isolation transformer, such as Radio Shack's 273-1374 (assuming it's still sold).

I would connect the transformer primary to the two signal wires from the PA's feed. Connect one wire from the transformer secondary to the signal lines of both the L and R (tip and ring) of the cable to the communicator. Connect the other wire from the transformer secondary to ground/return (sleeve) of the cable to the communicator. Depending on which gives less hum, connect or don't connect the ground/sheild from the PA's feed to the ground/return/sleeve of the cable to the communicator. (IIUC, that's what the hum switch does on the "crab" box.) If the verbal wiring diagram isn't clear, I could draw up a schematic.

Depending on signal levels, you might want some resistors to attenuate the signal. Better yet, after the transformer, run the signal to the communicator through a small mixer or a decent audio cassette deck from a thrift store--anything to give you manual gain control and a level meter.

russellhltn
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Postby russellhltn » Tue Sep 25, 2012 8:48 pm

rmrichesjr wrote:Depending on signal levels, you might want some resistors to attenuate the signal. Better yet, after the transformer, run the signal to the communicator through a small mixer or a decent audio cassette deck from a thrift store--anything to give you manual gain control and a level meter.


All things considered, I think a small mixer that can take a balanced input would be best. Simply because we know what the next complaint will be - that the remote sites can't hear the choir very well. Or the organ during the congregational hymns. Sure, you could jack up the podium sound, but that doesn't work all that well. Getting a mixer gives you a level control and a place to add a few mics for the musical numbers.
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Postby Mikerowaved » Wed Sep 26, 2012 2:13 am

RussellHltn wrote:All things considered, I think a small mixer that can take a balanced input would be best.

I couldn't agree more. In fact, if I may quote from the Meetinghouse Webcast Audio page in the Wiki...

It is strongly recommended that you use an audio mixer at the location sending the webcast.
In the Audio Components section, the webcast team recommends the Mackie 402-VLZ3, although I've found almost any small Mixer with an XLR input will work fine, such as this fairly inexpensive (< $40) Behringer XENYX502 5-Channel Mixer.
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