I am Pretty sure..
THF6a does not have Stereo Ability
Find one you think you would like to use. If it doesn't have the proper connector on it, put one on it. Kenwood has them 'ready-made' and so do several other companies.
- 'Doc
Heil Pro Elite with boom mike has stereo head set feeds and phase reversing switch..
Most Ham radios only have mono audio except some high end radios with two recievers.
To use the stereo head sets for mono you need to get conversion plugs from stereo to mono and or use the correct patch cords.
Look in Radio Shack for these plug adapters and mono cords.
Good luck.