If you’re having trouble hearing your CD player/MP 3 player etc. through the audio panel, you may be contemplating having your avionics shop do the procedure outlined in http://www.cirruspilots.org/members/adsb/cd/SA-01-12.pdf>Garmin*. Don’t.
I was considering this, because the volume from my wonderful, all-singing, all-dancing, expensive Archos Jukebox was too low to hear in flight. I was even prepared to pay the two-to-??? hundred dollars for the mod. But I know what’s involved, and I wan’t convinced that a typical avionics shop would be able to deal with the tiny surface-mounted components; they don’t usually do repairs at this level. Plus, Garmin warns that “Removing these four resistors may increase unwanted noise levels”.
After a little digging, I found that what the mod did was to match the input impedance of the Garmin 340 to the output impedance of most consumer electronics audio devices. That made it easy to fix, without increasing any noise levels, without paying for any up(down?)grade of my audio panel, and completely external (so no regulatory concerns). (It also explains why some devices work OK - they have non-standard output impedances).
I used two audio matching transformers (Radio Shack catalog number 273-1380), and a couple of stereo mini-plugs. I housed the parts in a 35mm film canister. Parts cost ~$5. It took less than an hour to build. Not something to try if you’ve never played with electronics, but easy if you have. Now I have to take care not to turn the volume up too high – and I have no “unwanted noise levels”.
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