(cont.) Furthermore, when I panned the sine waveform/tone 4 fully to the right, I still hear the DN from the piano sound (which is heard equally L and R) in the left headphone while the sine waveform is sounding/being played.

Then, there's the effect reverb has on the DN - reverb ("Hall 1") lengthens the duration (time) of the DN considerably (3 times or so longer), like the DN is reverberating as well as the waveform sound. (N.B. I know nothing of the physics of sound; I'm only reporting what I have observed!) Try this, stigf: Assign a sine waveform to a tone of a patch and mute all other tones of that patch (in your original experimental patch, mute tones 1-3). Set tone 4 volume level to 127 and pan to 0, then set the TVA ADSR envelope so that there is no S or R (attack: time - 0, level - 127; decay: time - 127, level - 127). Play the sound with the reverb (Hall 1) on, then off. With sustain and release set to 0 on the TVA envelope, I can easily hear the DN with reverb ON, but cannot hear it at all with reverb OFF. The same thing happens with other waveforms/tones with TVA envelopes set for AD only.

I don't know what all of this means, but thought stigf and others might be interested. Thanks for the original research, stigf! Best post on this BBS in a while!

As stigf mentioned and as I mentioned in a previous post on the "...ends in distorted fuzz" thread, it is really hard to notice the fuzz in the course of "normal" playing, sequencing, and recording. I had my XP80 for two years before noticing the DN and only noticed it because I went looking for it. I just bought an XP50 to take on the road (so my XP80 can stay in the studio) and it does not have the DN; however, I may have to sell it and get an XP60 with the DN for other reasons (read: the DN does not bother me!).