[TenTec] Audio Problem - off topic

[ron]

If ur friend wears an hearing aid, have him purchase a "loop-set" that hangs
around his neck. The connector is a stereo mini-plug. Switch the hearing-aid
to telephone pick-up and it'll sound like ssb is "inside" the his ears. 

Ron
Wb1hga

Rick writes:

Is there any add-on device that can be used to take the
rig audio and shift it up or down a few hundred hertz in an attempt to
optimize my friend's limited hearing range?