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Does anybody know if I can parallel the copilot headphone wire from the Comm to a cabin speaker?

I would like to not use a headset with the engine off while soaring. The variometer has its own external speaker so that is covered. I just would like to get the output from the Comm to a speaker without the trouble of an audio panel.

I do have a small 12V audio amplifier that the headphone wire could connect to which would power the cabin speaker. The on/off switch to the amplifier would enable or disable the cabin speaker is my thinking. I do not have any experience in design in this area so I have no idea if this is doable.

The paralleled headphone wire would see a different impedance on each branch but only one branch would be used at any given time.

Anybody have experience with this?

Rick Caldwell
Xenos 0057

Microair M760 transceivers have a direct output for a speaker so would assume other radios also have a suitable output.

Peter

Rick

Which radio do you have?

Gordon

Gordon,

I have the GTR 200. I see that there is a audio output for a recording device that I can use. It has 40mW (4.9 Vrms) with 600 ohm load. I see cabin speakers are listed as 3.2 ohms. I am guessing my audio amp will adjust as required but if it doesn't, perhaps a resistor in line will get it up to 600 ohms.

Rick Caldwell
Xenos 0057

You'll definitely need an amplifier since an intercom will require 3-5ish watts and the radio alone can't deliver that much power to a speaker.

You could probably connect the amplifier to the headphone wire. The input of an audio amplifier is normally relatively high impedance (like >10,000 ohm) so won't appreciably affect the signal to the headphone. Since it's available, though, I'd probably use the output intended for the recording device.

Any audio amplifier intended for that approximate power level is going to be able to drive 4, 8, etc., ohm speakers. Adding a 600 ohm resistor would be counterproductive--you'd end up with an intercom quieter than your headphones.

Thanks for useful the info, Chris.

Rick Caldwell
Xenos 0057

Why don't you use the speaker, or speakers, from an old set of headphones? Mounted behind your head in soaring conditions it might be a simple solution. I can hear radio traffic and ATIS while on the ground without the engine running when my headphones are sitting on the seat beside me.

Lou,

Thanks for the darn good idea. I don't have a cabin speaker yet but do have some junk headsets in the hangar. I'll try that out with the little amp I have. That should make them loud enough. I want to be able to listen to music that will be connected to the Comm on the Music port in addition to Comm chatter.

Rick Caldwell
Xenos 0057