Combining audio outputs

[filiperosa]

Hello,

My intercom has an audio input.

Can I connect togheter the audio output of my efis with the output of my transponder which has adsb warnings to the same input in the intercom?

Thanks,
Filipe

 

[gmkonrad]

Audio mixer

This will do what you want.
https://www.aircraftspruce.com/catalog/avpages/flightdataAP60audiomixer.php
I use one, works good.

 

[rv8ch]

No idea if Vern is still selling these:

http://www.vx-aviation.com/AMX.html

Another good thread:

https://vansairforce.net/community/showthread.php?t=89360

 

[filiperosa]

Thank you!

 

[vlittle]

No idea if Vern is still selling these:

http://www.vx-aviation.com/AMX.html

Another good thread:

https://vansairforce.net/community/showthread.php?t=89360

I don’t sell them, but Makerplane does:

https://store.makerplane.org/

The current version (AMX-10A) was introduced a couple of years ago to support the installation of OnSpeed systems in existing aircraft (converting mono to stereo, for exmple), and I took the opportunity to convert it to suface-mount assembly. Or as my daughter would say, ‘welcome to the new millenium, Dad’.

Datasheet: https://www.huvver.tech/wp-content/uploads/AMX-10A_install_A4.pdf

View attachment AMX-10A_install_A4.pdf

 

[filiperosa]

Thanks,

One question, what is the problem to just connect the two togheter?

Thanks,
Filipe

 

[Mikeyb]

Connecting the outputs directly essentially shorts them. Although not as foolproof as the mixers mentioned a resistive divider like shown in the photo will probably work. It might take some adjustment to get the levels right.

 

[filiperosa]

Thanks. In each device i am also able to control the audio level on the configuration

 

[BobTurner]

As stated previously, many (but not all) audio outputs have a very low impedance when looking ‘backwards’, e.g., they tend to ‘short’ each other out when two are connected together. A ‘mixer’ circuit prevents that. If you have just a few inputs then the circuit shown in post 7 works fine (I would use 330 ohm resistors) except that the maximum possible volume will be reduced by the resistors. This is only an issue if the max volume available is already marginal. It usually works just fine.

 

[filiperosa]

Thanks a lot!

 

[penguin]

A friend suggested an AU-401 audio mixer which he uses. I have not yet installed it so can't say how well it works.
AU-401

 

[BobTurner]

If you’re handy with a soldering iron you can build a mixer for about $1 in electronic parts. All the cost is for the connectors, the box, etc.

 

[vlittle]

As stated previously, many (but not all) audio outputs have a very low impedance when looking ‘backwards’, e.g., they tend to ‘short’ each other out when two are connected together. A ‘mixer’ circuit prevents that. If you have just a few inputs then the circuit shown in post 7 works fine (I would use 330 ohm resistors) except that the maximum possible volume will be reduced by the resistors. This is only an issue if the max volume available is already marginal. It usually works just fine.

Good tip. Page 5 of the AMX-10A document shows a passive combiner on the output using 150 ohm resistors. In this case, it allows the simple retrofit of a monophonic audio system to support stereo tones (OnSpeed retrofits, for example). We were asked to add OnSpeed to a number of demo aircraft, many of which only had mono audio systems. Amazing what a pair of resistors can do.

Vern