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Multiple voice inputs?

S

Steve Sampson

Well Known Member
Can someone point me in the right direction please?

I am beginning to think about avionics for an RV4. Since I built a -9A the number of instruments outputting voice has increased. This time I might have:

Radio
Dynon 180
Garmin 496
ACS AOA
IPOD

That is radio + 4. How do I merge all of these into a headset with some degree of priority? I am only seeing intercoms that can cope with the radio +2.

Thanks,
 
Hi Steve:

I found myself in a very similar situation. My intercom only has one stereo input for music + the headset line for audio.

Based on the recommendations from my intercom manufacturer I made a passive audio mixer. Most audio devices have enough gain that they can easily be passively mixed.

You basically just throw a bunch of resisters on each audio line and tie them all together. I actually soldered some ends of various resisters together along with an output line (which goes to the intercom's COM audio line). The other ends I soldered d-sub pins onto and inserted them into a db9 connector and then put them in a shell. This gives me various resisters of different sizes. You sort of have to swap your audio sources around until you get the audio levels to an acceptable level, although this is generally only a concern for sources for which you can't control the audio level (such as the Dynon).

I installed an audio jack into the bottom flange of the panel that I will use for a music input source. This jack is wired to the dedicated stereo music input on the intercom.

It all works perfectly. I have the following feeding my system:
Dynon EMS-D10
Dynon EFIS-D10A
Garmin SL-40

I will eventually install a Garmin 496 and I will also wire it into my passive mixer using just one channel (all I care about on the 496 is the voice alerts...i.e. mono). You also have to be careful to make sure the 496 audio ground is connected to the headset audio ground at the intercom. Not really a big deal.

2006-09-21.1734.jpeg
 
What radio?

Steve Sampson said:
Can someone point me in the right direction please?

I am beginning to think about avionics for an RV4. Since I built a -9A the number of instruments outputting voice has increased. This time I might have:

Radio
Dynon 180
Garmin 496
ACS AOA
IPOD

That is radio + 4. How do I merge all of these into a headset with some degree of priority? I am only seeing intercoms that can cope with the radio +2.

Thanks,
Click to expand...
Some radios like the Icom A200 have several 3 or 4 aux inputs, Garmin's don't. Also I'd encourage you buy an intercom that allows an aux stereo music input. A cheap intercom with an aux mono input is OK, but I would not scrimp on this if you want music (that is my opinion).

If you have a Garmin with out the aux inputs, you can do as above and gang all the alerts together with resistors and/or capacitors. I personally like a little pre-amp mix board kit for about $10. Aeroelectric has an expensive board kit he sells that will cost you about $60? It really an overpriced kit.

The nice thing about a pre-amp mixer is you can "tune" and balance the inputs and absolutely isolate them. However people have lots of success just jamming the wires together with a little resistor in there to isolate or balance gain (volume). I do like that it is passive, lighter and cheaper, so its worth a try, but I know a little mixer with op-amps to isolate and balance will work and be more adjustable.

I'd buy a stereo intercom (PS Engineering) that can handle a stereo input and headsets. I'd recommend DRE engineering intercom's but they went belly up. If you are cheap, on a budget, the intercom is not the place to save money IMHO, because you use it every flight. Its basic and critical to your enjoyment. I'd avoid mixing music and alarms together for many reason. There are many ways to skin the cat (who says that anymore, I guess me :rolleyes: ). The thumbnail on top my architect (with an Icom), with a Garmin I'd go this way (click to enlarge).



Here is a typical mixer (hidden under panel):
FK652a.jpg

http://store.qkits.com/moreinfo.cfm/FK652

Basically its an audio panel you can hide under the panel, no switches or anything. Comes on with master buss. Set and forget. You could have it so its volume "pots" are reachable under the panel. There are a half dozen electronic kits you can buy for $8-$14. The one above is just one I picked at random. You can go out an buy a little multichannel op-amp and the other parts, but these kits are cheaper.
 
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Is it possible to just get a 4 or 6 place intercom and run the alerts from the Dynon etc. into the extra inputs intended for headsets 3-6?
 
Its been thought of but not sure its been done

Guy Prevost said:
Is it possible to just get a 4 or 6 place intercom and run the alerts from the Dynon etc. into the extra inputs intended for headsets 3-6?
Click to expand...
You mean use the mic inputs? Hummmm I'd call the maker of the intercom but it might work. Some one ask that before and really inputs are inputs. I never heard back from the guy who was going to try it.

There may be some unforeseen down side, one is possible extra cost of the intercom not being cost effective? It might make pilot/crew comm difficult or annoying by using mic imputs. The radio will override the passenger mics, which may be a minor issue, may be not. The impedance and gain might mean you still need a resistor in there.

It could be perfect. I'd call the maker of the unit and ask. I would not pop for extra money to get a 4 or 6 place unit for this purpose.
 
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