I think I've seen other folks complain about using the USB connection to record. Mostly I've seen this in online groups on FaceBook. I'm not sure how many here actually use the Spark besides me. I'm sure there's probably a few.

So... to let us hear that wave... you have to upload it to a music hosting site such as DropBox, SoundCloud or something else similar. You then copy the active link to the song and post that in your thread post here.
Second thing.... tell us about the computer and sound card as well as the driver you are using to record this audio. Yes, this can be the source of the trouble and in many cases is.

Personally, I don't use the USB connection to record..... I prefer to use either a microphone on the amp, or use a connector that plugs into the headphone out and run that into the input of your interface. I use the direct headphone out into my Scarlett 99% of the time. That gives me a solid sounding copy of what the amp is doing.

The spark is one amazing little amp.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.