Thanks Bill, I missed your post about this but a dutchie informed me about the audiotrack links... I hope you forgive me?

As I wrote the original tracks contain a huge amount of noise. Your bitrate however was set to 320kbps and this is way 'overdone'.
I removed most of the noise usings Sony Soundforge noise reduction plugin.
The edited files are 192kbps bitrate and IMO sound much better.

It looks like your audio-mixer and/or soundcard generate the background noise. To solve this you probably need to upgrade to a better card.