This may be a bit off topic for this group, and if so I apologize... it
does concern "digital" signal processing rather than "digital" modes like
Pactor and PSK.

I'm looking for an audio DSP program that runs on a (fast) PC and provides
some of the audio DSP features that something like the MFJ 784B provides.

One would take the audio output from a receiver and feed it in the "line
in" port and get DSP'd and filtered audio output from the computer
speakers.

Anything like that available?

Thanks...