[Elecraft] Question on K3 Xmit and 8 MHz IF

[Dave C]

I have a Softrock receiver connected to my K3's KXV3 IF output and have
been using PowerSDR to provide a second receiver/panadapter.  I also played
around with recording QSOs using PowerSDR but I have noticed that the
transmit audio recorded in this manner is slightly off frequency.  So, the
receive sounds exactly on frequency but my transmit consistently sounds
high by about 75-100 Hz.  Can anybody explain why this is so?  If I listen
on a second radio, the K3 transmit sounds fine so I think it's on frequency
and that this little issue is some artifact of the Softrock/IF setup.

Other relevant notes:  The Softrock is calibrated against WWV in the cal
menu so it is good.  To record to a 20m USB QSO, I have the Softrock set to
LSB with a frequency of 8.2156 MHz.  The receive is okay there but the
transmit is off or high in pitch as noted.  I'd just like to understand why
that is so.

Thanks and 73,

Dave
K8JDC