Andy,

I also have a SignaLink USB, and find it works well with my Yaesu.
However, compared with 3 other sound card or external units I have
used, it seems to have a much lower impedance. The result is that it
loads down both the input and output. Obviously, how much depends on
your rig, and where you are connecting it.

I have an external switching box which I built up to allow the use of
some other devices with the rig, which of course includes an OFF
position. In your case, probably something as simple as a double pole
toggle switch built into a small box would work. It wouldn't hurt to
switch both the RX and TX audio.


--
Alan
WA4SCA