[Elecraft] Ground isolation w/K2 serial rig control

[Ben Hofmann K1NT]

Most sound card interface designs include isolation
between computer and radio signals using transformers
for audio and optoisolators or solid state relays for
PTT.  If one wanted to have a sound card interface
connected at the same time as the KIO2 or KPA100
serial control cable, the signal ground on the serial
control cable is not isolated, and so would provides
an unwanted ground path between the radio and the
computer.  Is there a way to isolate the receive data,
transmit data and signal ground lines of the serial
control cable such that this ground path is
eliminated?  I am looking for a homebrew solution as
opposed to a pre-packaged approach, but I can't seem
to find any info on the net besides pre-packaged.

-Ben  K1NT