Nightowl I accept the fact that my submissions will look pretty basic in comparison, but these tech issues on top just make matters worse.
Personally, I think the more advanced players benefit the greatest from attention to audio quality, since it increases my ability to discern nuance. The more simple the playing, the less it matters. At least to me.
If you are intent on spending time on it, it might be worth figuring out how to record the sound directly from your Donner. I don't imagine it's much harder than finding the right cord to go between the piano and the recording device. WieWaldi had a good plan for figuring out how to do it, though according to this video, you should try to connect through Port #2 and not through Port #5, which is strictly MIDI data. (Port #1 is stereo and Port #2 is mono, but the problem is that if you connect through Port #1, it disables the speakers, and you can't hear yourself play! There's a way around that, but it's probably not worth the trouble). That means you need a cord with a quarter-inch jack for the Donner end (I'm not sure if TS jack or TRS jack is what you need--contact Donner and ask if the OUT port on your DDP-80 accepts TS or TRS? Or give the TS a try first. Here's a guide--TS = 1 black band near the tip, TRS = two black bands), and whatever is proper for the recording device end (if it's a computer, it might be labeled MIC or AUDIO IN). If you go to any music store with a picture of your recording device ports, the staff should be able to get you the right cord.