Hello MarkV!
I have listen to the sound clip now. I can hear background noise and it sounds like when you do a recording without noise reduction, is this what you mean?
If this is the issue, try first to connect a noise suppressor between the guitar and the input of the amp, if it have no effect, try to connect the noise suppressor in the fx loop of the amp and see if it dissapears. This way you can determine if the preamp or the power amp that is causing this noise.
I also heard some fret buzz on some of the note you played.
The timbre in the amp sounds ok to me.
2B