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email(at)jaredyates.com
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 Posted: Sun Dec 10, 2017 9:41 am Post subject: Bose ANR Jacks and Grounding, Alternator AC Limits |
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In the course of investigating a possible ground loop in the audio system, I'm wondering if the Bose LEMO jacks might be to blame. As I understand the Bose instructions, it seems that the ground for the ANR system returns via the audio grounds. I have the LEMO jacks geographically adjacent and electrically parallel to the traditional 1/4" jacks, with about 4 inches of wire between them, with no shields. Wires going from the traditional jacks to the intercom are shielded with the shields grounded to the intercom back plate only.
Here is how I have the LEMO pins wired currently:
Pin 1 goes to a fuse on the main bus
Pin 2 goes to the sleeve on the 1/4 audio connector (Ground, audio low, goes to intercom audio low pin associated with the seat)
Pin 3 goes to the tip on the 1/4 audio connector (Left audio, goes to intercom)
Pin 4 goes to the ring on the 1/4 audio connector (right audio, goes to intercom)
Pin 5 goes to the ring on the .206 mic connector (mic high, goes to intercom)
Pin 6 goes to the sleeve on the .206 mic connector (mic low, goes to intercom)
The intercom is a PSEngineering PAR100EX, though the symptoms have persisted through a few intercoms. All mic and audio jacks are isolated from ground with insulating washers.
They symptoms are a faint crackly noise from the Skyview system that goes away when it is powered off, and RPM-dependent noise from the alternator that goes away when I de-energize the field. I measured 0.6 volts AC on the alternator output, but Plane Power says anything less than 1 volt is in spec. 1 volt seems a little high relative to the conventional wisdom I'm finding elsewhere. Does that sound reasonable?
I'm open to any troubleshooting strategies for trying to make the noise go away.
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donvansanten(at)gmail.com
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| Posted: Sun Dec 10, 2017 10:47 am Post subject: Bose ANR Jacks and Grounding, Alternator AC Limits |
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Jared,
I had the same noises on my last install of Bose Lemo plugs. I used the number 22 black with white stripe wire that is listed as the shield in the instructions.
All my other devices say to keep the shield grounds less than 4 in hes long.
I just finished a new install of two Lemo plugs and this time I cut the black/white wires off abd spliced the shields from the head phone and mic cables to the audio paneh shield wires. Perfectly quiet now.
I do not have the normal jacks in this plane but those long shield grounds on the Lemo plugs look to be the problem.
You said you did not use the shields, maybe removing the b/w wire and using a splice to the shields would help on your setup as well.
Don
On Sunday, December 10, 2017, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
[quote] In the course of investigating a possible ground loop in the audio system, I'm wondering if the Bose LEMO jacks might be to blame. As I understand the Bose instructions, it seems that the ground for the ANR system returns via the audio grounds. I have the LEMO jacks geographically adjacent and electrically parallel to the traditional 1/4" jacks, with about 4 inches of wire between them, with no shields. Wires going from the traditional jacks to the intercom are shielded with the shields grounded to the intercom back plate only.
Here is how I have the LEMO pins wired currently:
Pin 1 goes to a fuse on the main bus
Pin 2 goes to the sleeve on the 1/4 audio connector (Ground, audio low, goes to intercom audio low pin associated with the seat)
Pin 3 goes to the tip on the 1/4 audio connector (Left audio, goes to intercom)
Pin 4 goes to the ring on the 1/4 audio connector (right audio, goes to intercom)
Pin 5 goes to the ring on the .206 mic connector (mic high, goes to intercom)
Pin 6 goes to the sleeve on the .206 mic connector (mic low, goes to intercom)
The intercom is a PSEngineering PAR100EX, though the symptoms have persisted through a few intercoms. All mic and audio jacks are isolated from ground with insulating washers.
They symptoms are a faint crackly noise from the Skyview system that goes away when it is powered off, and RPM-dependent noise from the alternator that goes away when I de-energize the field. I measured 0.6 volts AC on the alternator output, but Plane Power says anything less than 1 volt is in spec. 1 volt seems a little high relative to the conventional wisdom I'm finding elsewhere. Does that sound reasonable?
I'm open to any troubleshooting strategies for trying to make the noise go away.
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Airdog77
Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia
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| Posted: Mon Dec 11, 2017 8:22 am Post subject: Re: Bose ANR Jacks and Grounding, Alternator AC Limits |
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Hi Don,
I have mine wired up like Jared's, still in build mode so can't test yet. But just to clarify your statement:
| Quote: | | I just finished a new install of two Lemo plugs and this time I cut the black/white wires off |
Meaning you cut them off totally? No other action with these 2 black/white wires?
| Quote: | | spliced the shields from the head phone and mic cables to the audio panel shield wires. |
Essentially per a traditional headset jack install?
Curious about this since my LEMO plug sits adjacent to the standard plugs. I wired per Bose instructions. My black/white wires connect to the white/blue wire (low) tab of the jacks.
Since the black/white wires are simply a wire extension of each cable pair (phone & mic/ptt) ground shield, is it fair to say in sticking with the LEMO+standard jacks configuration that IF I hear noise I should disconnect the black/white wires from each jack tab and subsequently wire each black/white wire into the respective standard jack's cable shields?
To be clear, my headset jack wire shields currently simply terminate (no connection) at the jack end and are just "floating."
Cheers,
Wade
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_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com |
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