View Full Version : AOA Pro II harness

01-19-2012, 06:28 PM
I'm just installing the AOA Pro II wiring harness and noticed there is a single audio wire, which I connected to the tip connector of my headphone jack. If I just want to get audio alerts thru my headphones , is there any reason to connnect the single wire marked COMM to anything or just leave it unattached?

Rob Hickman
01-21-2012, 12:32 PM
The COMM wire is actually the ground wire and needs to be connected to your ground buss.

Depending on your intercom or radio it might not work having the Audio connected to the headset tip. It really should be wired to the audio panel.

01-21-2012, 08:51 PM
Ok, Rob, I can see from the wiring diagram that pin #1 labled COM goes to aircraft ground buss.
I have a sigtronics SPA-4S intercom that is already prewired to the Garmin SL40. Referencing your wiring diagram in the notes section, I have a single shielded wire labled AUDIO that says " connect the inner conductor to either an audio panel input, intercom input OR directly to the tip of the pilots audio headphone jack". I have connected it to the tip of the headphone jack and left the shield wild. Is this acceptable?

Rob Hickman
01-22-2012, 05:14 PM
I dont think that it is going to work with the SL40 tied to the same port, have you tried it?

Does the SPA-4S have unswitched audio inputs?

01-22-2012, 09:56 PM
Rob , I'm trying to attach a wiring diagram of my SPA 4 intercom system, not sure if this is coming thru.
I am just in the stages of installing the instrument panel and completing the wiring, nothing has been powered up yet. I can see where I would like to be able to control the volume of the AOA announcements to my headphones. A harness was prewired for me before I bought the Pro II AOA for my SPA interphone , an SL-40 and a garmin 496. Looking at the SPA4 diagram I'm thinking I should tie the Single shielded audio wire into the J1(3) blue wire going into the interphone. It looks like the J2(1) Green wire goes out to the tip of each headphone jack. The only switching I have is a Avionics Master switch. All the radios have their own on/ volume controls. Does this look correct?

Rob Hickman
01-24-2012, 10:15 AM

I found this on their web site, you should ask Sigtronics how to connect audio inputs to it.

01-25-2012, 02:18 PM

The Aux input to the blue wire of the SPA-4S will interrupt the music. The Aux input will be heard simultaneously at all headset positions with the intercom and radio. Make sure during installation that the alarm output has sufficient output (300 mvP-P) to trigger the squelch of the intercom.

The volume control of the intercom only controls the intercom volume. The volume of the alarm must be controlled by your Advanced Flight System.

Mark Kelley
Sigtronics Corporation
178 East Arrow Highway
San Dimas, CA 91773
Phone: 909-305-9399
Fax: 909-305-9499

I got this reply from Sigtronics. Question is : does the AOA audio alarm put out 300 mvp-p

Thanks for your help

Rob Hickman
01-25-2012, 03:29 PM
Not sure, it is designed to drive a standard 600 ohm load. I suspect that it will work fine.

01-25-2012, 08:45 PM
Ok,Rob, I'll give it a try

Unrelated to this subject, is it ok to mount the manifold pressure switch on the engine side of the firewall. I'm using a Sam James plenum over the engine, so I don't think the heat under the cowl would be that high except while taxiing. I would like to mount it high on the firewall above the brake fluid resevoir to keep the firewall penatrations to a minimum. Do you see any problem with this or is it to hot under the cowl for that switch

Rob Hickman
01-26-2012, 08:54 PM
It should be ok.