[CQ-Contest] SO2R audio click

[Paul Young]

I have tried a several circuits for audio switching in my SO2R
box - some using relays and some using active parts, and in all
cases there is sometimes a noticeable click when switching
between radios.

The click is only present when there is a strong signal and does
not happen all the time.  I believe it is due to quickly switching
from a non-zero instantaneous voltage to zero.

Does anyone have a circuit which suppresses the click?  I'd prefer
not to have to use dual voltages (+/- 15) or surface mount parts.

                                 Paul, K1XM