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AUX Input

WingnutWick

WingnutWick

Well Known Member
Hello!

I am writing to see the feasibility of installing an AUX audio input into my comm system. How is this done?

Thank you
Wingnut
 
Charles,

It would help if you indicated what plane this is for and described your current panel configuration.

A really easy way to do this is by buying and using a Quite Technologies Halo Headset. https://www.quiettechnologies.com/

The Halo's have a 3.5 mm female stereo jack built into them with volume control. I use the Halo's and have my Garmin Aera 660 audio plugged in there so I get audio alerts, works great.

There are of course other ways of doing this.
 
Garmin 340 Audio Panel ??

It really depends on the panel's audio equipment. If you have a Garmin 340 you can go to the Garmin website and download an electronic copy of their installation guide and it will identify what pins you need to connect to at the back of the audio panel for the music function. Pay attention to the audio music checkout detailed in the installation guide (section 2.6.6) - in my aircraft's case, I had to connect a ground to J2 pin 15 because the decibel level was too low to hear. Radio Shack sells an audio input jack that works pretty well. Just pay attention to how you wire it up.

One word of serious caution. Garmin d-sub pins are high density sub pins and require a special tool to crimp them to your wire. These crimping tools are quite expensive however you can get a very good but less expensive version from SteinAir. They also sell the high density d-sub pins you'll need. SteinAir also has several excellent U-Tube videos on making wire connections which I strongly encourage you to view before starting the project.
 
Garmin 340 Audio Panel ??

It really depends on the panel's audio equipment. If you have a Garmin 340 you can go to the Garmin website and download an electronic copy of their installation guide and it will identify what pins you need to connect to at the back of the audio panel for the music function. Pay attention to the audio music checkout detailed in the installation guide (section 2.6.6) - in my aircraft's case, I had to connect a ground to J2 pin 15 because the decibel level was too low to hear. Radio Shack sells an audio input jack that works pretty well. Just pay attention to how you wire it up.

One word of serious caution. Garmin d-sub pins are high density sub pins and require a special tool to crimp them to your wire. These crimping tools are quite expensive however you can get a very good but less expensive version from SteinAir. They also sell the high density d-sub pins you'll need. SteinAir also has several excellent U-Tube videos on making wire connections which I strongly encourage you to view before starting the project.
 
The hi density pins can be crimped in the same crimper as the standard pins. But you do have to control how deep into the tool you insert the pin, since the stop doesn't work properly on the hi density pins.

Relatively inexpensive crimpers are available that adjust for both pins, as well.

Charlie
 
Crimping tool

SteinAir also sells a special insert that fits inside their crimper that is for high density sub pins. It's cheap.
 
Tankerpilot75 said:
SteinAir also sells a special insert that fits inside their crimper that is for high density sub pins. It's cheap.
Click to expand...

They do; I've got one. But I've done so few hi density pins that I usually just manually position the pin so the crimps happen at the correct point.
 
AUX with ICS

Hey guys!

Thanks for the replies, sorry I was out of internet connection for a while there. So a little more amplifying information here. Aux inputs are for music. I want to install them in the front and aft cockpit so you either one can plug in and play the music over the ICS for both to hear. I have the PM501 ICS and have attached the wiring diagram. I see that there is an input for the AUX. Am I able to place the two inputs together to that one terminal so both work? If so, how do I shield the splice?

I've also attached a photo of the jack I have. I see three prongs coming out. I attach one to terminal 1, where do the other two go (I assume one is a ground). I've pretty novice at the wiring bit and reading the diagram so pardon my ignorance.
Thanks guys.

Wick
image1.jpg

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Last edited:
Is that a 1/8" jack, similar to the audio out on a cell phone? That's probably what you will want for a music input.

The terminals are likely, left, right, and ground return, making a stereo jack. Your intercom is a monophonic (one audio channel of output) model, based on your schematic.

It's not hard to do what you want, but is a bit convoluted. Assuming that you'll be using a cell phone or an ipod type music source that's designed to drive headphones, here's what to do.

Get a handful of 1/4 or 1/2 watt resistors. any value between 500 & 1 thousand ohms will work fine, just make sure they are all the same value. On each left and right terminal of your jacks, solder a resistor lead (4 resistors, total).

Assuming that you'll only use one jack at a time and *don't* try to play 2 music sources at once, do this:

At each jack, solder the free leads of each resistor together, and solder the center conductor of a shielded cable to that joint. Solder the shield to the ground terminal of the jack. You can either run both lines to the back of the intercom, or 'daisy chain' the jacks (easier & cleaner). Assuming the daisy chain technique, the cable would start at the rear jack, go to the front jack, and then the center wire would go to pin 1 and the shield would go to the intercom's chassis ground.

Reason for the resistors: Music source will almost certainly be stereo, and the pair of resistors form a 'summing' network to feed both channels to the intercom's single channel input, while isolating the two channels from each other. Because you're only using one jack at a time, the resistors on the other jack are effectively out of the circuit.

Now for the unknown. Some consumer music sources cannot supply a high enough level to work through an a/c intercom. If your music volume is too low, you can add a preamp between the jack(s) and the intercom input. (Different subject)
 
Follow on questions

rv7charlie,

Thank you for the detailed response! Yes it is in fact a 3.5mm 1/8th stereo jack.

I have a couple questions...

I am planning on using an iPhone/iPod to play music. Do you think this will be sufficient to provide adequate volume output without a preamp?

What happens if I use both jacks at one time?

If I decide to just go with one jack, same process with the resistors for just that one?

Thanks again for the help!

Charles
 
WingnutWick said:
rv7charlie,

Thank you for the detailed response! Yes it is in fact a 3.5mm 1/8th stereo jack.

I have a couple questions...

I am planning on using an iPhone/iPod to play music. Do you think this will be sufficient to provide adequate volume output without a preamp?

What happens if I use both jacks at one time?

If I decide to just go with one jack, same process with the resistors for just that one?

Thanks again for the help!

Charles
Click to expand...

The quickest way to know about levels is to just try it. If you want to know before cutting metal, go ahead and add enough wire to the correct pins in the intercom, long enough to make the run you'll need to make. Get a pack of alligator-clip leads (won't be the last time you use them, once you have them). Use them to temporarily hook up one of the jacks (with resistors), and try it out. No reason to not fly it like this; worst thing to happen is something comes unclipped & it doesn't work. If levels are high enough, you can proceed. If not, then you can look for a preamp/isolation amp.

If you try to use both jacks at once, you'll get very hard to interpret mashup music. :) With the series resistors on all channels, it shouldn't damage anything, but in addition to the nonsense, both sources may be a bit more distorted and/or lower volume.

With one jack, you'd just need the 2 resistors.

Note that one big advantage to adding a preamp (the right kind), is that it can be a 'summing amp', or mixer, so that you can have multiple inputs somewhat like you'd get with a full fledged audio panel. For instance, audio from a separate nav radio, audio alerts from an EFIS, stall warner, etc. A good summing amp will have no (practical) limit to the number of inputs, just by adding input resistors.

Hope that helps,

Charlie
 
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