Headset Compatibly

[Potter1]

Could some one please offer some advice?

I have three DC 13.4 headsets, two are several years old and one I purchases last week. The two older ones work without a problem. When I use the new headset by itself that works fine, but when I plug one of the older 13.4’s into the intercom with my new one the microphone on the new headset hardly works.
I can hear the person with the older 13.4 and also anyone on the radio, but they cannot hear me.

I can’t believe that it’s a compatibility problem as they are all the same model.


P....:confused:

[aztec25]

I have the same headset (bought in 1996) and I flew with someone last week also with the same model although his was only bought in the past 8 months or so. It wouldn't communicate until I used an HMU (headset matching unit) on mine. They must have changed the spec.

I rarely get mine to work with any other headset unless I use the HMU though I too expected it to work with the same model. They must have changed the spec of the microphone.

The HMU costs about £50 + vat

Az

[PA38]

From memeory I think it has something to do with impedance, between an electret and a dynamic microphone the two ain't compatable...

[bluskis]

DC headsets have had compatibility problems for years, and when I mentioned my problems to an airline friend, he confirmed they also had had problems, so were careful to stick to known pairs which are compatible.

I failed to solve my problems with an HMU, so from memory I returned both headsets to the distributer, who made the necessary adjustments/repairs/replacements of mike? and they have worked fine ever since.

However when another pilot/ examiner tries out his own headset in my aircraft, it inevitably is incompatible, so they have to use one of my matched pair.

Hope this info helps.

[Keef]

Been there ... done that. I wonder why the various headset manufacturers can't agree on the spec for the microphones!

Don't lash out lots of money on a "matching unit". All it takes, from the experience of the "ANR conversion team", is the right value resistor in series with the microphone: it can be fitted in the plug.

The resistor goes in the lead of the one that CAN be heard when they are both plugged in. Typically, 220 ohms will do the job. A bit of experimentation can find the right value - you may need to go higher.

If the one with the resistor gets too faint by the time the "good" headset can be heard, then stick a 22 uF capacitor across the resistor.

You should find that the "good" headset can be heard fine when you're pressing the PTT the side it's plugged in, because the PTT should disable all the other microphones on the system.

No, I don't fit the resistors "on commission".