Routing wires for headsets/mics

RVNewsletter · Post by **RVNewsletter** » Mon Nov 16, 2009 9:01 am

AeroElectric Connection cautions against running headphone/mic wires with wires carrying current. I'd kinda like to bunch the wires together for a beter appearance. I've already got too many different routes for wires to follow. In the advice above, does this include, say, the power cable for the Icom A210 and , for example, the power for the PS Engineering 1000II intercom? The latter, especially seems to be pretty low current. Is there a threshold to consider in this or just stay away from all power-carrying wires altogether?

cjensen · Post by **cjensen** » Mon Nov 16, 2009 9:34 am

I have mine bunched in with wires carrying current. Everything is low current though. I've been told (by the experts none-the-less!) that as long as it's not high current (alternator or strobes), that noise won't be an issue.

Post by **bullojm1** » Mon Nov 16, 2009 9:54 am

Bob,

I wouldn't worry too much about this. The shielding on the headset/mic wires offers a great level of protection from EFI. Like Chad said, you only have to worry about wires that carry large current that pulses. Alternator, strobe and wig-wag could cause issues. However, I wouldn't worry about it too much. I have all of my wires bundled together.

RVNewsletter · Post by **RVNewsletter** » Sat Nov 21, 2009 9:41 am

Shielding brings up another question, then.

I see a lot of disagreement on the question of shielding on headset/mic wires.

The ICOM A210 schematic, for ex, does not show shielding terminating at the radio, but does show it terminating at the audio panel or (in my case) the PS1000II. This would be for the auxiliary jacks, which I realize not everone installs but which PS says is required.

But I've also heard people say that the shielding should be grounded at both the jack and the audio panel, tho the PS schematic seems to show it terminated only at the intercom end.

Then you have Bob Nuckols who says you don't even need shielded cable, you can just use a twisted pair. He uses the multi-conductor shielded cable, he says, for aesthetics and ease, they being under one insulation and all.

Is this the headphone equivalent of a primer war?

Post by **Spike** » Sat Nov 21, 2009 3:25 pm

I believe so. I have always thought it appropriate to shield at only one end, generally the one that plugs into the electronics. The reason was fuzzy, but it might have been to prevent ground loops, etc.

hydroguy2 · Post by **hydroguy2** » Sat Nov 21, 2009 5:22 pm

yep, I went with ground one end also.

of course I also went tailwheel, rattle can primer, tip-up...mine probably be lucky to get off the ground

svanarts · Post by **svanarts** » Sat Nov 21, 2009 7:03 pm

Another vote for grounding the shielding at the intercom end. That's what I did on the -4. No noise. However, I think you probably could get away with no shielding. These runs are so short that I don't think it really matters.

Post by **bullojm1** » Sun Nov 22, 2009 8:08 am

Bob-

All the shielded wires I have on my airplane are only connected to ground at one end only (well, except the mag, but thats a little different). For example, the shielded wires between my audio panel and A210 is grounded at the audio panel side. All the runs to my pilot/copilot jacks are grounded at the audio panel as well.

I am pretty sure the headset/mic jacks get grounded just by nature of how they are hooked up to the three conductor wire when everything is connected. Be sure to also buy isolators for your headset/mic jacks so they aren't locally grounded at the airframe. B&C and I think Stein sell the isolators. They eliminate any chance of a ground loop.

captain_john · Post by **captain_john** » Sun Nov 22, 2009 10:39 am

hydroguy2 wrote:yep, I went with ground one end also.

of course I also went tailwheel, rattle can primer, tip-up...mine probably be lucky to get off the ground

Sounds like a good plane to me!!!

I agree with this strategy. I have heard the grounded point being referred to as a "drain" by electronics geeks. They "drain" the noise at the source.

...and Spike is right. If you ground it at both (or multiple ends) you can end up with ground loops. (even on a nose dragger! hahahaha)

CJ

MachineMan · Post by **MachineMan** » Sun Nov 22, 2009 4:41 pm

I am planning on using this to wire the headset/mic jacks.
http://www.bandc.biz/22awgshieldedtriow ... lwire.aspx

captain_john · Post by **captain_john** » Sun Nov 22, 2009 6:25 pm

Rich, You may want to hold your fire before pulling the trigger on that wire.

Albeit nice wire, if you are ordering the harnesses that go with the Approach Fast Stack... I think it comes with the wire!

CJ