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Need Audio Mixer for Radio / Dynon Alerts

647jc

647jc

Well Known Member
I'm installing a Flightcom 403d intercom and a single radio and don't want to install an audio panel. I want to use the intercoms aux input for music and I will also be installing a Dynon EFIS / EMS with audio warning capabilities. I need to MIX the Dynon audio output with the radio output before feeding it into the intercom. I know some people do this with a couple resistors (kind of crude) but I would think someone sells a simple mixer that would provide this function. The airplanes mission is a simple day / night VFR RV9A and I DONT want to install an audio panel to achieve this fairly simple (and hopefully inexpensive) function. Any ideas / suggestions (except installing an audio panel) would be appreciated.

Thanks,
J.C.
 
Two ideas:

If you use a (modern) four place intercom, you can use the extra inputs for the audio or dynon. Of course, no fancy auto muting on these inputs.

The impedance of these inputs is about 560 ohms or some such, so you could try feeding both of the sources through a 560 ohm resistor (one resistor each) and then connecting them to the music input. But I'd test it to see how it sounds.

Dynon -> 560 ohm -> music input <- 560 ohm <- other source

btw: I think if you open up most 'aviation grade' simple mixers, you'll find two resistors. :D
 
The resistor mixer is simple, cheap and reliable. However, in order to adjust the audio level, I recommend a 10K ohm potentiometer in series with the Dynon audio output.

For more information, see this audio mixer design. It's for a Sigtronics intercom, but the principles apply in general to mixing audio sources on the headset bus.

You'll need to download the pdf.

Vern Little
 
Oh Duh! again. The Flightcom 403d stereo intercom I'm using is actually a 6 place unit and I'll only be using 2 of the places. So, I will have an extra 4 mic inputs, one of which I can use for the Dynon alerts.

J.C.
 
Aux inputs on Com Radios

647jc said:
Oh Duh! again. The Flightcom 403d stereo intercom I'm using is actually a 6 place unit and I'll only be using 2 of the places. So, I will have an extra 4 mic inputs, one of which I can use for the Dynon alerts.

J.C.
Click to expand...
Not sure you want to use the Mic input on the intercom for OTHER audio. These are VOX inputs for low gain mic inputs.

Most if not ALL Comm radios have a few aux inputs. That will be fine for the Dynon warning. I know my ICOM A200 has many aux inputs for audio input from other radios or a warning signal like you want.
 
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