Comment by eatmyshorts

OK, if you say so. I think you're misunderstanding a fundamental concept of digital to analog converters. But if you think it's just to prevent blowing your speakers, that's OK.

The reason that square wave sucks is because it introduces tons of high frequency content (your amp probably won't reproduce the high frequency content anyway, so I don't think most Japanese consumer amps will damage your speakers--that is, the amp will act like a filter anyway). That high frequency content then creates alias effects (think of moire patterns when looking at super high-res photos that are scaled down without anti-aliasing). Those alias effects sound like shit to the human ear.

The point of filtering is to anti-alias the resulting analog signal after conversion from digital to analog. The point of upsampling is to move that filter well beyond the audible range, so you can use a 1st-order filter (gentle slope, but it introduces no phase effects). The fact that a square wave hurts your speakers is inconsequential--the amp will effectively filter the signal anyway. Unfortunately, it will filter the signal without anti-aliasing, which introduces those nasty interference patterns within the audible spectrum (that is, if you feed a straight 44.1KHz sampled square wave to your speakers without upsampling/filtering).