Thanks, everyone...I'm now using an audio interface. I've also tweaked the settings in Real Band (making sure the sample rate in RB matches Win 10, and forcing RB to record in mono even though it's receiving a stereo signal from the interface).

Jim Fogle, thanks for the tip about the piezo pickups at 1,500 Hz. I'm EQing out some around 2,000 Hz and that helped a lot. I also read (on a fiddle forum") that "bow rumble" comes in around 200 Hz.