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headset wiring question

prkaye

Well Known Member
I have a wiring harness for an ICOM radio. In the harness, the pins for Phones(-) and Mic(-) are electrically connected. Out of the other end of the harness there is only one wire that is electrically connected to both pins. Is this typical? When i install the phone and mic jacks, should the (-) of both be connected in common?
 
I have a wiring harness for an ICOM radio. In the harness, the pins for Phones(-) and Mic(-) are electrically connected. Out of the other end of the harness there is only one wire that is electrically connected to both pins. Is this typical? When i install the phone and mic jacks, should the (-) of both be connected in common?

It is fairly common. Both eventually go to ground. Some manufacturers keep them separate in the harness and some don't.
 
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Yes, this is so common that those pins are often called ‘ground pins’ and are connected to a common ground. However, some of the better audio panels will isolate the mike (-) from common ground, to help alleviate stray noise pick up. Obviously if you have such a panel, the mike (-) has to be kept isolated.
 
Yes. Not unusual to have the audio "-" wires connected this way. The 2 audio "-" wires are connected to a single wire that terminates at "audio common" which is a ground point either on the back of the audio panel tray, or (with some audio panels) to a ground pin on the audio panel connector.
 
The 2 audio "-" wires are connected to a single wire that terminates at "audio common" which is a ground point either on the back of the audio panel tray

Ok seems simple enough. Can this "Audio Common" wire be connected to the aircraft ground (forest of tabs) instead?
For the Jacks themselves, should the common leads be wired to the same audio common, either on the radio tray or aircraft ground?
 
Ok seems simple enough. Can this "Audio Common" wire be connected to the aircraft ground (forest of tabs) instead?
For the Jacks themselves, should the common leads be wired to the same audio common, either on the radio tray or aircraft ground?

In theory, any ground should work. In reality, in an electrically noisy environment, best practice is to run the (- or ‘common’) wire from the mike side by side (or twisted pair, even better) inside a shielded cable, with the - or common connected to any dedicated ‘mike low’ input, if it exists, otherwise to a ground near the mike hi input. Connect the shield to a ground close to the mike hi input, but only at the radio end. No shield connection on the other end. Wire the headphones the same way.
 
Ok seems simple enough. Can this "Audio Common" wire be connected to the aircraft ground (forest of tabs) instead?
For the Jacks themselves, should the common leads be wired to the same audio common, either on the radio tray or aircraft ground?

A lot of folks say "ground is ground". But, as soon as you start powering stuff up, that's no longer 'perfectly' true.

Its a good practice to keep all your audio lo and audio common terminations, including shield drains, separate from your power grounds. Thats why many audio/intercom manufacturers either provide a ground lug on the back of the tray, or have detailed in their wiring diagrams complex daisy chains of wires leading back to the panel's "chassis ground".

As far as headphone audio to the jacks, are you going to use an external audio panel or intercom? Or, will you use the internal intercom that the A-2xx iCom radios have?
 
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