[Elecraft] PSK audio problems with K2

[Stephen Prior]

Can anyone shed any light on this please?

I have connected tx and rx audio from/to the computer via isolation
transformers on both audio in and out.  Rx works fine.

However, I have hit a problem trying to get acceptable transmit audio
quality.  I have the K2 stripped back to 10W at the moment so am not using
my external KPA100 in order to remove that from the equation.  I am feeding
the audio from the computer via the isolating transformer straight to the
microphone header with the microphone removed.  I have turned the compressor
off in all modes.  I have no ALC showing and have tried the power control in
various positions.  The audio is extremely rough with various artifacts
spreading widely above and below the tx frequency.

I have the K2 feeding into a 100W Bird dummy load.  I have listened both
with my K1 with a few inches of wire as an antenna and my TS-480HX in the
car parked outside.  Same grotty received audio.

I have checked the carrier balance on the ssb board.  Although still audible
in the K1¹s receiver I have minimised it for usb and lsb.  I note that I can
eliminate it almost altogether for lsb, but then the level at usb is high.
So it¹s a compromise as I have read it would be.

I have tried both my desktop pc (a mac) and my Dell laptop (XP) - no
difference.  I have listened directly to the audio output from the computers
­ it sounds right.

I must have used psk31 on a dozen or more radios in the last ten years or
so, but never hit this severe a problem before.  Listening to my ssb speech
via the HM12 microphone, it doesn¹t sound great, but yet I am using the K1
to listen to it with so that¹s not too surprising.  I don¹t use ssb at all
except mobile, so have had no operating experience of the K2 in this mode.

I am wondering if the problem lies deeper somewhere.  I have googled, but
hit nothing useful.

Any thoughts would be much appreciated

Thanks and 73,

Stephen G4SJP