D1000 to GMA 340 volume deafening.

madb1rd

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I have chosen to install my Skyview into the GMA 340 music port 1 because it is muted during all other communication. Frankly in SoCal airspace radio communications are far more important than most of the reasons the Skyview wants to blather at me about.

However, the D1000 output is deafening. I have it set to 001 and it is still very loud. I'm presuming a resistor would help, any advice on what Ohms would be a good place to start?
 

madb1rd

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OK, I was hoping to just pop a fixed resistor in there if anybody knew what it should be. I'll start with a POT to experiment and post what resistance I come up with. thx Jake
 

madb1rd

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Well, I had some 5k POT so tried them, and they made no difference. I tried a fixed 10K resistor and it didn't seem to do much either... all of which seems surprising. Guess I'll try a 100K 10 turn POT and see what that does.
 

madb1rd

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Well, I had some 5k POT so tried them, and they made no difference. I tried a fixed 10K resistor and it didn't seem to do much either... all of which seems surprising. Guess I'll try a 100K 10 turn POT and see what that does.
In thinking about this I used the POTs as a two lead rheostat in series versus connecting the third lead to ground. Is the latter configuration the better strategy?
 

madb1rd

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Well, Alas, I'm not finding it in the install manual. It actually gives the contrary statement "When interfaced with such devices, they can generally be used with any input designated as an auxiliary input without any external resistors or other components needed between the SkyView and the intercom."

The D10EMS had a POT volume control arrangement. But I'm not seeing that here?
 

vlittle

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Use 50 ohm resistors on the audio lines to ground. And yes, it's written somewhere.
This will also reduce any noise from the SV. Turn up the volume on the SV after you make this mod.

VV
 

madb1rd

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Use 50 ohm resistors on the audio lines to ground. And yes, it's written somewhere.
This will also reduce any noise from the SV. Turn up the volume on the SV after you make this mod.

VV
Hmmm, just did a search on the current install manual for "Ohm" and it only says there is 50 Ohms impedance on the source for the audio outputs. I will try my test POTs tying the audio leads to ground, thx.

And to update, I went to test it again and it changed such that the volume is now substantially lower. So it appears the electrons are having their own little party outside the normal laws of physics... dare I mention the "I" word... "INTERMITTENT"
 

madb1rd

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Following up on this thread....
I have to fib on myself. I was in the middle of testing how to fix this problem when it suddenly went from way too loud to "can barely hear it." Spent a couple of hours measuring and flying and stuff until at 2am my brain figured out the copilot squelch had been turned off so the audio panel was muting the Dynon input even though there were no headsets attached. The Dynon was so loud it was still making it partly through the mute function.

However, with that straightened out I found that creating a voltage divider by using an 8.2K Ohm resistor in series for each audio line with a 1.8K Ohm resistor to ground on the Skyview side of the 8.2K resistors brought the volume down to less than eardrum popping levels.
 

Rhino

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Ummmm 8.2 + 1.8 = ? ;)
Wait. Wait. That question was on final Jeopardy just last night.....

However, two resistors in series aren't a voltage divider unless he tapped off an audio connection between them. So yes, he may have the total recommended 10k in series on each output. But if he tapped between the resistors to get the audio output, he isn't using the full 10k. Probably would have been easier just to use a simple 10k resistor inline, but if it works, it works. I'd probably go with a pot on the panel so I could adjust volume on the fly, but I was in electronics, so I have a hard time resisting little customization projects like that.
 

madb1rd

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Actually, 10K in series did nothing partly because impedance on both ends is so much higher. But per my narrative above you can't add the resistors together to get anything meaningful. For each side, left and right, there is an 8.2K in series. And on the SkyView side of that 8.2k resistor is another 1.2K that goes to ground. This is a voltage divider circuit. I didn't go with two POTs because who needs more holes in the panel when it can be adjusted internally in the SkyView and really does not need to be changed with any regularity.
 

jakej

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FWIW, I never put the potentiometers for that purpose on the panel - I remotely mount them behind the panel as once I have them ‘set’ they don’t need to be changed ;)
ps - you can still ‘tweak’ them later if need be.
 

vlittle

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You really don't need the series resistor.... the output impedance of the SkyView allows you to put a terminating resistor to ground to knock the level down. I used 50 ohms, but YMMV.

Nothing wrong with the voltage divider technique... it just costs $0.02 more.

And here is a sneak preview.... The ever popular AMX mixer family is coming back to production after a couple of year hiatus. MakerPlane will be offering these... on their storefront by 'kosh. This particular image mixes two mono fixed level inputs and four pairs of stereo inputs (two pairs fixed, two pairs adjustable). It's called the AMX-10A and it was developed for the OnSpeed team to enable the retrofit of stereo audio to any aircraft audio system. Variants include the AMX-2A (10 channel mono), and AMX-4A (5 stereo channels, with two adjustable channels).

For those unfamiliar, the finished product is contained in a D-subminiature backshell, which makes it very easy to retrofit. It can also directly drive headsets, and does not require an intercom to function. Many intercoms support stereo inputs, but they are muting (blocked by comms traffic). This solves the problem. [note: Dynon's intercom does not mute the stereo input on the back, which simplifies things].

Vern

Screenshot 2022-06-14 111541.jpg
 

Rhino

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swatson999

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I have chosen to install my Skyview into the GMA 340 music port 1 because it is muted during all other communication. Frankly in SoCal airspace radio communications are far more important than most of the reasons the Skyview wants to blather at me about.

However, the D1000 output is deafening. I have it set to 001 and it is still very loud. I'm presuming a resistor would help, any advice on what Ohms would be a good place to start?
I have my SV1000T audio output going in to Alt Warn on my 340, no resistors or POTs or anything needed, and it's working fine. Perhaps it's because you're using the Music input and not Alt Warn? Yes, the muting when receiving from ATC is nice, but really, how much does your SV send out an audio alert?

Plus, there's the "times ten gain" thing described in section 2.6.6 of the Installation Manual.

Might that be part of the problem?
 
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