I've listened to most software players with Wav files and Foobar sounds about the best.

Why do different players sound differently, and what does Foobar do to sound so good?

Some of the worst sounding players are Windows Media Player and iTunes.

The only other software I've heard that sounds better is Samplitude, which is a professional editing package.

...placebo effect

there's so much more to FB2K than this..

well yes and no...a well written decoder that outputs 24 bit or 32bit-float and a good card..will sound better than something that decodes to 16 bit. you ever played mp3s in mediaplayerclassic? its pretty sad. and yeah, samplitude (&fb2k) rule the world..

I suggest you have download all those players and have somebody play the same file with every one (no dsp's) in a blind random "test" before you make that statement.

even if youre simply playing back .wav files, which should remove the more obvious differences between mp3 decoders, theres still a lot that can go wrong to reduce the playback quality. a simple volume control, when not internally calculated at a higher resolution...will cause rounding errors and loss of quality - if youve reduced the volume 12db, your bit depth is down to 14 bits, assuming the material was even peaking at 0db to begin with...then it may be sent to a driver level mixer and further degraded, etc. so youre welcome and encouraged to abx other players if you want..but at the end of the day, i wouldnt chalk it entirely up to a placebo effect...better math means better sound..