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Inexpensive audio panel recommendations?

Ed_Wischmeyer

Ed_Wischmeyer

Well Known Member
My RV-9A has a FlightTech ITC-402P intercom, and there are problems. Audio quality is good in Isolate mode, but in the ALL mode, there's lots of noise.

No, I have not debugged all the wiring to the copilot side, but the symptoms may indicate an internal problem.

The existing radio is a GTN650, hooked directly to the intercomm with 150 ohm resistors on the comm and nav signals, and with the G3X alerts coming through another resistor (they're not working yet). I thought it would be real cool to use a GTR200 as the intercomm, hooking up the GTN650 through one unswitched audio input with a simple toggle switch for, granted, limited but adequate audio panel functionality. I'm still looking for somebody else who appreciates this brilliant idea but have decided instead to take the hint and abandon the idea.

I really don't want to spend a bunch of money for an audio panel with lotsa features I don't need or want. Anybody got any good suggestions? Or does anybody have an SL-15 looking for a really good home?

thanks

Ed
 
Van's sells a blind audio mixer. It only makes sense to use a mixer if you are sourcing with two com radios though.
They are not really designed to solve intercom issues.... unless you go with a high end unit like PS that has intercom built in.
 
If you have some free time you can do what I did: build your own intercom, with mixers on the front end for as many inputs as you want or need. The most expensive parts are the knobs. I use the radio's volume controls as listen/don't listen. A single switch moves the mic and PTT between coms. Passengers have their own volume controls for radio and music, so if they want music and you don't, just turn your music volume all the way down. If you don't want to hear the passengers turn your intercom volume down. If they don't eant to hear you, turn your squelch to off.
I can send you the schematic if you're interested. Nothing hard, but some small parts to soldered

Bob
 
Ed, the kit version of that 25 pin mixer is only $75. But I don't remember if you are a homebrew electronics guy or not. It is small and detailed work, but easy if you have experience.
 
Ed_Wischmeyer said:
But I also need an intercom- the one I've got doesn't work well.
Click to expand...

Before giving up on the existing intercom, can you supply more detailed info? Most simple intercoms tend to have one summing amp for all the mic inputs, with perhaps another amp for the radio input.

What kind of noise do you hear (hum, buzz, roar, etc). Does it do it with nothing plugged into either mic jack? With only the pilot mic plugged in? If you plug in both headsets (both mic & ear) and switch to isolate (where the pilot phones are quiet, right?), do you hear the noise in the passenger phones?

Charlie
 
One thing to check before it gets too complicated Ed, is why the intercom is noisy. You said in isolate mode, it is good. Is it breaking squelch when not needed, in normal mode?
If not, and the characteristics are just plain background noise.... look closely at what the other microphone is doing.
The RV9A is loud. No way around that reality.... at least easily.
If the passenger does not place the mic very carefully... at their lips, it will induce cabin noise to a large degree.
If the headset is simply sitting on the seat, while solo... by all means set the intercom to isolate.
I have tested this position sensitivity in my 9A with Lightspeed microphones and have seen a large change when moving the mic a small amount.
Recent testing I have done in an OV-10 Bronco, with Lightspeed mics show the same results. And it is a very loud aircraft.
The noise cancelling dynamics are crude, compared to that in the earcups.
Other brands may fare better. What headsets are you flying with?
 
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Ed_Wischmeyer said:
Flying with Lightspeed Sierras.

Lots of things to check tomorrow - thanks, all!

Ed
Click to expand...

Do the tests I suggested on the ground, without the engine running.

If you only experience the problem in the air (or with the engine running), it's probably a squelch issue as has been mentioned.

EDIT: Might also be worth finding some passive headsets, too, just to be sure they aren't causing any issues (though that's pretty unlikely).

Charlie
 
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With two lightspeeds plugged in:
- left headset, a little louder and clearer in Pilot only mode than in All;
- right headset less clear, slightly louder in the All mode

With other headset unplugged:
- left headset, as above;
- right headset, same volume in both positions, less clarity as before
 
Hi Ed,

Sorry, but you have to be more specific and clear in your descriptions. What does 'louder' mean? (Louder noise? Louder audio?)

Did you do the test with engine off, or running?

Describe the noise. Is it a whine? (alternator, only with engine running)

Is it static, crackling sound? (possible alternator, if varies with rpm. possible noisy semiconductors in intercom; *might* vary with icom volume)

Is it hissing, 'whooshing' sound? (also likely noisy semiconductors in intercom)

Is it amplified external cockpit noise? (insignificant with engine off; worsens with engine rpm/airspeed)

Does swapping headset positions (pilot/copilot) have any effect?

To work, troubleshooting has to be methodical, documented, and one change at a time.
 
Took a look at the install manual for your intercom. From the description of the pilot isolate switch, it basically removes the intercom from the pilot headset circuit, leaving it connected directly to the primary comm.

That obviously eliminates the intercom as a noise source, but it also eliminates any noise coming *into* the intercom from a noisy electret condenser mic (on the other headset) and/or noise coming into the intercom from another source through its aux or music inputs.

To narrow the noise source down to the intercom itself, you'd need to ensure that there's no connection to the copilot mic input, the music inputs, and the aux input.

FWIW, your idea to use the intercom built into a GTR200 should work, with proper implementation of the summing resistors and external switches. The wiring diagram of the intercom section of the GTR200 looks like a typical a/c intercom.

Charlie
 
We gave the intercom system and headphone jacks a good once over and found nothing wrong with the system. I really think the intercom has an internal hardware issue. We have decided to go ahead and install a Garmin GMA 240.
 
Mike H said:
We gave the intercom system and headphone jacks a good once over and found nothing wrong with the system. I really think the intercom has an internal hardware issue. We have decided to go ahead and install a Garmin GMA 240.
Click to expand...

Mike,

Great decision! We are confident you will love the GMA 240.

We have been painfully watching all this discussion about using resistors to connect multiple audio streams in parallel including a GTN 650 COM/NAV and G3X alert audio just hoping that you would make this decision!

For about $845 for a new GMA 240, you really can't go wrong with this solution.

Thanks,
Steve
 
PMA5000EX

Mike H said:
We gave the intercom system and headphone jacks a good once over and found nothing wrong with the system. I really think the intercom has an internal hardware issue. We have decided to go ahead and install a Garmin GMA 240.
Click to expand...

Hi Mike, did you look at the PMA5000EX and compare it to the GMA240?

$100 more but does provide IntelliVox and more flexibility

I hope that others on this forum who are using our PMA5000EX might chime in with their experiences audio panel.
 
mscheuer said:
Hi Mike, did you look at the PMA5000EX and compare it to the GMA240?

$100 more but does provide IntelliVox and more flexibility

I hope that others on this forum who are using our PMA5000EX might chime in with their experiences audio panel.
Click to expand...

I've used several PS panels and have never been disappointed.
I've also used several Garmin panels, and they've never been as good. Only you can decide if it's worth the extra $100.
 
mscheuer said:
Hi Mike, did you look at the PMA5000EX and compare it to the GMA240?

$100 more but does provide IntelliVox and more flexibility

I hope that others on this forum who are using our PMA5000EX might chime in with their experiences audio panel.
Click to expand...

Mark, I initially suggested the PDA 360EX. I figured it would fit right in with all of the other incredible equipment in the panel, but Ed decided it cost too much and that he would not use the features that it offers. I did suggest the PMA500EX as well, but Ed made the decision to buy the GMA320.
 
g3xpert said:
Mike,

Great decision! We are confident you will love the GMA 240.

We have been painfully watching all this discussion about using resistors to connect multiple audio streams in parallel including a GTN 650 COM/NAV and G3X alert audio just hoping that you would make this decision!

For about $845 for a new GMA 240, you really can't go wrong with this solution.

Thanks,
Steve
Click to expand...

Steve, I was just doing what I was told. I was all for installing a new audio control panel at the start of the project, but I an not paying the bills. I have tried integrating multiple audio sources into an intercom with similar results as we had in the -9A.

I am currently installing two more G3X touch systems, one in a -4 and one in a new-7.


The owner of the -7 only wants a single com radio so I suggested the remote mount GTR 20 due to the built in intercom. Does the intercom in the GTR 20 have unswitched inputs that will work with the G3X audio inputs?

The -4 has a single nav/com with a PS intercom. The owner wants to be wire the G3X audio inputs into the intercom through resistors. I think we may end up with similar issues as we did with Ed's -9A.
 
Steve, I was just doing what I was told. I was all for installing a new audio control panel at the start of the project, but I an not paying the bills. I have tried integrating multiple audio sources into an intercom with similar results as we had in the -9A.
Click to expand...

I always try to accomodate the customers request on panel upgrades but they don't always understand the problems that can arise from trying to "improvise" in an effort to save a few dollars. So I feel it's my job when we plan things to say "no I won't do it like that because you won't be happy with it".

I've lost a few jobs because the customer thought he knew more than me and wanted something installed or interfaced that I wouldn't do, and I have no problem with him going somewhere else.

Sometimes you just gotta say "NO".
 
Mike H said:
I am currently installing two more G3X touch systems, one in a -4 and one in a new-7.


The owner of the -7 only wants a single com radio so I suggested the remote mount GTR 20 due to the built in intercom. Does the intercom in the GTR 20 have unswitched inputs that will work with the G3X audio inputs?

The -4 has a single nav/com with a PS intercom. The owner wants to be wire the G3X audio inputs into the intercom through resistors. I think we may end up with similar issues as we did with Ed's -9A.
Click to expand...

Hello Mike,

Yes, the Garmin GTR 20 and GTR 200 COM radios both have AUX1 and AUX2 unswitched mono audio inputs that are perfect for connecting the audio alert signal from a G3X Touch display.

Additionally, they both support a stereo music input, and of course provide a full feature 3D stereo intercom with wide range auto squelch feature that works equally well with the engine off on the ground, or when airborne at high power settings/noise levels.

Let us know if you have any additional questions.

Thanks,
Steve
 
g3xpert said:
Hello Mike,

Yes, the Garmin GTR 20 and GTR 200 COM radios both have AUX1 and AUX2 unswitched mono audio inputs that are perfect for connecting the audio alert signal from a G3X Touch display.

Additionally, they both support a stereo music input, and of course provide a full feature 3D stereo intercom with wide range auto squelch feature that works equally well with the engine off on the ground, or when airborne at high power settings/noise levels.

Let us know if you have any additional questions.

Thanks,
Steve
Click to expand...

Thanks Steve!
 
Walt said:
I always try to accomodate the customers request on panel upgrades but they don't always understand the problems that can arise from trying to "improvise" in an effort to save a few dollars. So I feel it's my job when we plan things to say "no I won't do it like that because you won't be happy with it".

I've lost a few jobs because the customer thought he knew more than me and wanted something installed or interfaced that I wouldn't do, and I have no problem with him going somewhere else.

Sometimes you just gotta say "NO".
Click to expand...

I have told customers no many times before and I absolu agree. In this scenario i was doing the work for a friend and told him he was screwing up, he now believes me :D
 
Mike H said:
The -4 has a single nav/com with a PS intercom. The owner wants to be wire the G3X audio inputs into the intercom through resistors. I think we may end up with similar issues as we did with Ed's -9A.
Click to expand...

Mike?

Is my project about to become $900 more expensive? :)

Though currently working very very well, I am not entirely opposed to parting with it.
 
You're call, but I think you are screwing up trying to integrate multiple audio inputs using resistors as well.
 
Paul - your oil changes are my kind of oil changes! That's gonna be a sweet set up.

Mike - you're a busy man. By the time I'm putting the G3Xs in my plane, you're going to be able to do it blindfolded:D.
 
60av8tor said:
Paul - your oil changes are my kind of oil changes! That's gonna be a sweet set up.

Mike - you're a busy man. By the time I'm putting the G3Xs in my plane, you're going to be able to do it blindfolded:D.
Click to expand...

Yeah, you will be number four! I could have had my -14A almost ready to fly by now but.......oh well. That's what friends are for, just be ready to shoot rivets soon.
 
Payback

Mike H said:
just be ready to shoot rivets soon.
Click to expand...

There has to be SOMETHING productive I can do with my safety scissors! Although I'm reading Aeroelectric Connection again and watching Stein's "how to" youtube videos, At this rate I'll be able to wire your panel! (probably not)

Jon: Things escalated very quickly. I will be bringing everyone out for drinks when I pay off the discover, all on my cash back rewards. Honestly, if I had brought the correct oil filter back from my spruce visit…I would have been re-cowled and flying! Very excited to learn however.
 
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Mike H said:
just be ready to shoot rivets soon.
Click to expand...

Always ready:D. Picked up some paint tonight. If it ever stops raining in the evenings maybe I'll get some interior sprayed and be ready to shoot here again as well.

Icarus said:
Things escalated very quickly...Very excited to learn however.
Click to expand...

Sure did;). For the second year in I row, I drooled all over the team X tent at OSH. What an awesome system!
 
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