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Author Topic: T368 600 ohm balanced line input. Need help.  (Read 2372 times)
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ke7trp
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« on: January 16, 2010, 10:28:43 PM »

Got the T368 up and running.  Carbon mic has to go.. LOL

I made a nice Break out cable for it with the mating connector for the back. My lines are RX mute, PTT and 600 Ohm audio.

The audio does not work.

Pin D is 600 ohm audio input.
Pin E is 600 ohm audio Shield.

I also have a Ground pin.

I cant figure out how to wire this correctly.  If it was balanced it would have TWO conductors and the shield would go to Ground.  My Audio rack has XLR's. I cut a mic cable and ran it into the Connector. One conductor goes to Pin D and one to Pin E. I put the shield on the Case of the connector. This makes sense to me but not to the radio...

How can it be balanced if its only two wires?

Should I hook the shield to the shield pin? Then what do I do with the other signal wire?

Clark
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K5WLF
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« Reply #1 on: January 17, 2010, 10:21:03 AM »

Clark,

I'm no T368 expert (never used one) but I speak fairly fluent audio. The truly proper way to match the 600 ohm balanced line to the unbalanced input would be with a transformer. Lacking that, try connecting XLR Pin 1 to T368 Pin E and Pin 2 from your XLR to the T368 Pin D. Just ignore XLR Pin 3 (unless you want to reverse the phase of your audio going into the 368).

HTH,
ldb
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WA1GFZ
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« Reply #2 on: January 17, 2010, 10:38:28 AM »

Connect your shield to the case of the connector. Do not bring it into the rig through a pin. Any RF on the shield should be terminated to the case ground of the rig. If you bring the shield into the rig it will put RF currents into the rig audio section.
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ke7trp
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« Reply #3 on: January 17, 2010, 10:46:25 AM »

The shield is on the connector case.   The TWO center conductors of the mic cable are on D And E.  This has NO audio at all. As I increase gain, I get a LOUD tone.  I am at a loss on this one. 

C
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