Actually, the best explanation of the settings is at the PS Audio website. You can bypass the multiwave settings and continue to use the Sin mode, or you can choose a multiwave setting, which as I recall mixes sine waves of different frequencies. The PS2 setting uses 60 hz or multiples thereof, I think, and is the only one they recommend for turntables, tape decks, and (probably) air pumps. The others use sine waves which won't work with those types of motors, so they're different frequencies, I guess. I found a similar effect before I used the multiwave at the 90 hz setting, but the hum from the transformer in my upsampler was too much, so I had to stick with the 60 hz setting. I find that the multiwave upgrade gave me the benefits of additional transparency and air that I got at the 90 hz setting without the drawbacks, but in addition the thinness you refer to, which was more noticable to me above the 90 hz setting but was there to some extent even at 90 hz, was gone--much better as far as harmonic richness, for lack of a better description. Ultimately, to my ears the upgrade was just about as big an improvement as the original unit, particularly since I had to use the original unit only at the 60 hz setting. I also think it's a significant improvement over the 90hz setting that I liked but ultimately couldn't use. Hope this helps.