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Aux audio question

Mike S

Senior Curmudgeon
My new plane is using a Trig com radio, and it has a single aux audio input.

I have three devices that I want hooked up for audio warnings over the headphones, AOA, the EIS and a CO detector.

Any idea how to do this simply and cheaply??

Can I just simply tie the three lines together or will that cause a problem?

Thanks in advance.
 
Mike-Get three 470 ohm resistors, put one 470 ohm resistor in series with each line, then tie them together and feed it into the Trig?s aux input. The resistors will provide some isolation but will also reduce the volume. If the volume is too low, you can buy an Op Amp and a few parts to build a real mixer circuit. About $1 worth of electronics. Let me know if you need to go this route.
Bob
 
The resistor is one way to do it quick and dirty. It will work, but you very well might find that 470 is a LOT of attenuation. Depending on what your sources are of course.
 
Carlos, thanks for the idea------I have no idea if something like that would work, perhaps someone who understands things electronic could render an opinion ???
 
The resistor summer described above should work fine. If you want one source louder, lower the resistor value. Quieter, the opposite.

See the Passive Mixer here

It uses 150 ohm resistors, but any value between 150 and 600 should work fine.

Vern
 
The resistor summer described above should work fine. If you want one source louder, lower the resistor value. Quieter, the opposite.

See the Passive Mixer here

It uses 150 ohm resistors, but any value between 150 and 600 should work fine.

Vern

Bamm ! What Vern and Bob said, simple. I just figured using a variable pot would let you adjust the audio up and down without having to change the resistors. Love electronics and it's slooowly coming back. :p
 
Mike, the GRT efis units have a menu option for adjusting the volume of the alert tones....
Carlos’ pot scheme is probably not the best way for mixing signals. If one signal requires max volume it will tend to drag down the others’ volumes.
Technical stuff: What happens is that the output of an audio circuit often has a low impedance when looking backwards, into it. E.g., if you connect two of them together they tend to short each other out. With a resistor in each line, you lose half the signal but that’s better than losing it all. As you add more and more inputs eventually you lose too much and need to add an amplifier...
Edit: you can start with a variable resistor for the input that has no volume control, adjust it until the volume is good, then replace it with fixed resistors. I try to stay away from remote mounted pots, after a while they vibrate to a new setting and then you’re digging under the panel to fix it...
 
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Bob, I was thinking I could use trim pots and just put one in each feed-----only hook up wiper add one side of the resistor and leave the third pin open.

0-500ohm units should do the trick.

Trouble is I would most likely need to build a board with them on it, and then find someplace to mount it.

Fixed resistors-----now that would be simple to just do the entire setup in shrink tube.

Now If I can find a local source for the resistors............
 
Bob, I was thinking I could use trim pots and just put one in each feed-----only hook up wiper add one side of the resistor and leave the third pin open.

0-500ohm units should do the trick.

Trouble is I would most likely need to build a board with them on it, and then find someplace to mount it.

Fixed resistors-----now that would be simple to just do the entire setup in shrink tube.

Now If I can find a local source for the resistors............

What about this? You could do like you're saying and use pots and when you get the audio levels you like you then measure the pots and have a better idea of the final fixed resistor size you want to buy?
 
What about this? You could do like you're saying and use pots and when you get the audio levels you like you then measure the pots and have a better idea of the final fixed resistor size you want to buy?

Yep, that would work also.
 
3.5mm mixer

Hey Mike,
I used a usb powered 4 into one 3.5mm mixer. If I can find it online, I will post the link.
 
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