car stero

[larry]

I put a pioneer car stero in my longez for music and I want to listen thru my aviation headset.  I also have a  King KMA 24H.  My volume is very low and I suspect an impedence mismatch is causing the low volume.  The volume is ok when running thru 8 ohm speakers.   Any ideas???   thanks   larry

[Joe Dubner]

Larry,

Your suspicion is correct -- the voltage at the 8-ohm output of the stereo is too low for the higher input impedance of the intercomm.  When I did my (mono) setup a couple of years ago I used a tiny 8-ohm to 1000-ohm matching transformer with good results.  With a stereo intercomm you would need two transformers: one on each side.

I dislike putting Radio Shack parts in my aircraft or recommending them to others but in this case I made an exception and bought their 273-1380 transformer for about three dollars.

BTW, it would probably be a good idea to put a dummy load (i.e. 10-ohm, 10W resistor) on the output of each channel of the stereo.

--
Joe