Need Audio Help...

I have GTN 650, Sorcerer, MVP-50 Engine Monitor, GDL-88, and 8000B Audio Panel.
All audio messages/warnings (traffic, engine, autopilot, everything) are very weak (unintelligible) and full of static.
Radio, intercom are all good.
Any and all ideas much appreciated.

Does the static go away with the engine shut down? Alternator off? That might isolate the problem a little more.

Makes no difference--unfortunately. Thanks for your reply, Dave.

It kind of comes across as a gain issue. Much of the following are things I assume that you may have already checked.

Are all the inputs from these various devices on independent inputs on the PSE8000? unswitched audio #1-#3?

Are you using a PSE harness or one you built? Have you validated all the wiring and that shields are only connected to the back of the PSE8000?

What are the output gain of each device set to?

Bob, many thanks for your input;

rleffler said:

It kind of comes across as a gain issue. Much of the following are things I assume that you may have already checked.
I bought this airplane flying so I'm fishing my way thru it. I'm puzzled as to how both 8000B radio inputs can be good--all ALL of the others be bad? Perhaps they use different grounds--which I have not yet discovered.

Are all the inputs from these various devices on independent inputs on the PSE8000? unswitched audio #1-#3?
They appear to be--but have not verified all of them.

Are you using a PSE harness or one you built? I'm pretty positive it is not a PSE harness-unfortunately. Have you validated all the wiring and that shields are only connected to the back of the PSE8000?
Grounds/shields were the first thing that I thought of--but have not verified all of them yet.

What are the output gain of each device set to?

I must confess that when audio folks begin to talk about "gain, op-amps, impedance, etc.", it makes my head hurt and my flux capacitor discharges. It appears that the gain on all of the 8000B inputs is set to 1:1. Am I correct in assuming that the device outputs should also be 1:1? I do not know how to check that on the various devices--hopefully it's in the literature.

Click to expand...

BTW, before the purists berate me with "You're not allowed to work on that!"--just lemme say "I know that."

jarvis said:

Bob, many thanks for your input;


BTW, before the purists berate me with "You're not allowed to work on that!"--just lemme say "I know that."

Click to expand...

What do you mean, you're not allowed to work on it? If it's an EAB, you can work on anything. Now, PSE may not warranty the intercom, but that's another issue.

I have a PSE8000BT and a GTN650. I don't have the other devices you have. On the GTN650, in the setup menu, there are volume settings. I would validate that they are set to 75% or more of the given range for the setting. You can always change it later if it's too loud.

My suspicion is that either the output volume on your devices are turned down, or you have a wiring issue.

You may want to recruit a friend to take a look at the wiring. A problem many of us have, including me, is that you can't see the forest because all the trees are in the way. When we make a mistake, we tend to consistently over look it. Where a fresh set of eyes may see it in an instant.

Also, did you wire the whole harness? The reason I ask that in the GTN650 install manual, starting at rev 2 or 3, one of the connectors illustrations was a mirror image and printed backwards. It was corrected in rev 7. If you used the pin out tables, they were correct. If you are a visual guy and used the illustrations like I did, you wired things backwards on one of the connectors. I don't recall what pins were on the impacted connector.

Trouble-shooting electronics remotely is pretty much guessing, but here's my guess: Bob's guess is right, you will find the builder connected all of these devices to the same unswitched intercom input. When it didn't work he turned the volumes (in those devices that have that option) all the way up (which is why there's a lot of noise). As you surmise, one device may look like a short to the others, which is why the signals are so weak. If you can, power down all but one of the devices to the unswitched inputs, see if that one by itself works okay. Repeat for the others.

Unpleasant step one is to trace the wires, make sure only one device per unswitched input. Since the builder may have crimped multiple wires together anywhere, you'll need to trace them all the way back to the sources.