Walter wrote:
Hi Don,
Honestly this is the first time in all these years I've been asked this question. The doc is specifying the Ohms of the speaker, so this is not necessarially the output impedance. I've submitted your question to our hardware team, will let you know what I learn.
-Walter
Thanks, Walter. I would like to know--but because my situation is unusual, there's no sense in you guys spending much time trying to figure it out.
In case you're curious about my setup: The intercom is built into the radio, an XCOM 760. Its external audio input impedance is intended for devices such as handheld radios and iPods, which have about a 5 Ohm output impedance (Z). Anyway, I know it works nicely with outputs from Dynon's D10A and the AP74 autopilot module; and a landing gear position alert; and a Sporty's SP-400 handheld transceiver that I use as comm 2. They all work just fine together.
Unfortunately, the external audio input to the XCOM does not have a dedicated volume control. It expects that the input volume will be adjusted by the audio source, instead. So that complicates the problem somewhat.
My mixer box has a pot for each input and a 500 ohm resistor in series with each jack. The combined audio signal plugs into the intercom.