Quote Originally Posted by IanLaw View Post
Many thanks again Ron - that sounds like good advice and I'll look into all that you suggest, before attempting to adapt my old helmet(s). I bought both helmets about 50(!) years ago, I guess, in an old "Army & Navy" store, probably for the equivalent of a few Dollars.

This will be an interesting project for me and I'm looking forward to having a go, if I decide to try to adapt just one helmet.

Ian
Ian: The plug you need for your mic is a 0.206" diameter PJ068 type - they are sold by many outlets including Aircraft Spruce: http://www.aircraftspruce.com/catalo...paneljacks.php

The headphone plug is a PJ-055 which is the standard 1/4 inch "phone" plug. Widely available.

I would not worry too much about driving a 300 Ohm headset with a low-impedance source; I use my 600 Ohm AKG K240 stereo phones on a computer sound card intended for 32 Ohm 'phones all the time and they work fine. If you are low in volume a 8 to 600 Ohm transformer available (used to be!) at Radio Shack will work fine. But I bet you won't need it. Driving a low impedance load with a high-impedance source is where you run into trouble.