Hi dro,
Winamp has, and early beta versions of WACUP had, a preferences option to enable or disable dithering in the playback group of options. This option in WACUP was removed several beta versions ago. I see that the recent out_neo.dll plug-in lists a dither filter in it's list of processing filters. If WACUP does support dithering via this plug-in, do you plan on providing a way to disable it?
I've read that dithering is the process of adding a small amount of random noise to a digital audio signal in order to reduce the distortion caused by quantization error. This technique is crucial for maintaining audio quality during the conversion process from analog to digital, and it can greatly improve the overall sound of a digital recording.
I don't know what kind of dithering (if any) was used by the encoders used to make my mp3s. I also don't know what the dither filter in out_neo.dll does. I don't think there is any significant distortion in my mp3s, but being able to disable the dither filter in out_neo.dll will let me tell if I can hear any difference with it enabled or disabled (and which sounds better).