Intercom and Headset Compatiblity

istrumit · #1 02-24-2017, 10:07 AM

Hi everyone,

I have a G900x. I love it. Absolutely love it.

But what I don't love is that my intercom has failed twice (second time was under warranty).

I have had an avionics shop test out the wiring, etc...and everything seems solid.

This all seemed to start when I bought two extra headsets for my back seaters.

Prior to that, I only had the two headsets for the front.

I have two Telex, one David Clark, and one off-brand (which I actually like the best). None of them are ANR. The Telex are stereo. The other two are mono. One of the Telex also had to go out for warranty service (failed completely).

My question:

Could some sort of load mismatch be contributing to the intercom failures ? Maybe I should get all stereo or all mono ? Or perhaps all the same brand of headset ?

I am mystified by the two intercom failures happening less than 3 months apart and I don't have clue whether its just bad luck on the re-man unit or whether there is something else afoot.

BobTurner · #2 02-24-2017, 11:44 AM

You understand that if you plug a mono headset into a stereo jack, you are directly shorting one channel to ground. Modern intercoms can handle this abuse, but some older ones cannot. Cheap insurance is to go to Radio Shack and get a stereo plug to mono jack adaptors, and plug the mono headphones in thru these.

rvbuilder2002 · #3 02-24-2017, 12:46 PM

Quote:

Originally Posted by istrumit

Hi everyone,

I have a G900x. I love it. Absolutely love it.

But what I don't love is that my intercom has failed twice (second time was under warranty).

I have had an avionics shop test out the wiring, etc...and everything seems solid.

This all seemed to start when I bought two extra headsets for my back seaters.

Prior to that, I only had the two headsets for the front.

I have two Telex, one David Clark, and one off-brand (which I actually like the best). None of them are ANR. The Telex are stereo. The other two are mono. One of the Telex also had to go out for warranty service (failed completely).

My question:

Could some sort of load mismatch be contributing to the intercom failures ? Maybe I should get all stereo or all mono ? Or perhaps all the same brand of headset ?

I am mystified by the two intercom failures happening less than 3 months apart and I don't have clue whether its just bad luck on the re-man unit or whether there is something else afoot.

A little info regarding what brand / model intercom you have might be helpful......
The stereo Flightcom intercoms come with switches to mount beside the headphone jack to select between mono or stereo headsets.

rv7charlie · #4 02-24-2017, 01:05 PM

Quote:

Originally Posted by BobTurner

You understand that if you plug a mono headset into a stereo jack, you are directly shorting one channel to ground. Modern intercoms can handle this abuse, but some older ones cannot. Cheap insurance is to go to Radio Shack and get a stereo plug to mono jack adaptors, and plug the mono headphones in thru these.

Uh, that might not do it. Many of those adapters just tie L & R channels to each other, making each channel see the other's output, which is worse than a dead short. They're more useful as input combiners, where the source current (mic or preamp) isn't strong enough to do any damage, and you just suffer a loss of level.

A workaround that is effective is to put a resistor (anything between 300 & 600 ohms works fine) in series with each output channel of the intercom. It will drop overall level by a couple of dB's, and provide protection for the output stage in those older intercoms that don't have protection built in.

Charlie

istrumit · #5 02-24-2017, 01:21 PM

Quote:

Originally Posted by BobTurner

You understand that if you plug a mono headset into a stereo jack, you are directly shorting one channel to ground. Modern intercoms can handle this abuse, but some older ones cannot. Cheap insurance is to go to Radio Shack and get a stereo plug to mono jack adaptors, and plug the mono headphones in thru these.

Bob - no, I did not know that. Although this is a modern intercom, I will go and get the adapters..thank you for than information !

rvbuilder2002 · #6 02-24-2017, 01:26 PM

Charlie is correct.
A radio shack adapter wont solve it if the problem is a mono headset into a stereo jack.
You still haven't said what intercom you have so there is no way to help you with whether that is even a problem or not.

istrumit · #7 02-24-2017, 01:31 PM

OK...more research then.

The G900X intercom is a GMA 1347, which is stereo and stereo headsets are recommended per the manual.

I guess I could just purchase two more stereo headsets and ditch the old mono ones.

koupster · #8 02-24-2017, 02:20 PM

They can be converted to stereo if you like.

Cheers, David

BobTurner · #9 02-24-2017, 07:31 PM

Quote:

Originally Posted by rvbuilder2002

Charlie is correct.
A radio shack adapter wont solve it if the problem is a mono headset into a stereo jack.
t.

I mostly disagree. One channel may see the output impedance of the other, which may be low but it won't be zero (which is what you have with a direct short). But most of the time the channels are balanced (radio and mike inputs are mono) and no current will flow back into the amp, e.g., no extra current flow. It's only with true stereo inputs that you may have an issue.
But to be extra safe, yes, put a 330 ohm resistor in series with each channel. And use the adaptor so you hear all the music.