Thanks alot for the positive response to my posting! I agree with you Wilkes, the DN appears stronger when the reverb is on. I believe this has to to with the fact that the reverb makes the total signal decay slower, so that it spends a longer time below the "critical level". If the level drops fast, it will spend shorter time in the critical area, and the noise gets less audible. The fact that the DN appears also when only reverb is present, rules out the possibility of the DN coming from the synthesis-engine itself.
I think the most important part of our discovery, is that the DN will not be present when the level on the output is above the "critical level". And it is not just that it is difficult to hear it; it is not there AT ALL, not even teoretically. This means that my sequenced songs have NONE of this noise until the end of the song. I can live with that!
Nice work Wilkes!
Stig