These things are little high-quality digital audio recorders. They're smaller than most portable compact-cassette recorders - actually, they're approaching the size of an old microcassette dictation recorder - but they have sound quality that the old concert bootleggers could only dream of. These sorts of recorders come with built-in microphones, of far higher quality than the mics in any small portable recorder before low-power portable audio-processing hardware and low-cost Flash RAM made this sort of device possible. You could have put super-high-quality mics on an old cassette recorder if you wanted to, but it was pointless; nothing you could stick in even a large pocket could record good enough audio to justify expensive mics.
(Yes, I know there were some relatively small analogue-tape field recorders that gave very good results - usually because they recorded on something better than a cassette - if you plugged a quality mic into them. There was probably also some integrated-microphone doodad that recorded on small reel-to-reel tape or Type IV cassettes with Dolby S or something, about which I just haven't happened to hear. But modern digital field recorders are still amazing, all right?)
Anyway, Linder set up all three recorders next to each other, and talked and then played guitar into the built-in microphones. Then he posted the audio from the three recorders, for his readers to audition.
Overall, the commenters opined that the H4 was OK, the H4n was better, and the PCM-D50 was best. They were pretty much unanimous that the difference between the H4 and the Sony was as plain as day - compared with the Sony, the H4 was "muddy" or "muddled", "disjointed", "scrambled", or slightly noisier; one commenter called it "not even worth talking about". One guy even said he heard wow and flutter. There was general agreement that the Sony was clearly superior.
The only problem with all this - which another commenter soon discovered - was that Brad actually screwed up. Instead of pasting in the embed code for all three recorders, he pasted in the H4 code, then the H4n code... and then the H4 code again. He just labelled it as the Sony PCM-D50.
So the first, and the third, sound clips were precisely identical. On account of being the same sound clip twice. But the one that was labelled Samson Zoom H4 sounded lousy, and the one that was labelled Sony PCM-D50 sounded great.
Psychoacoustics: It ain't just a river in Egypt.
Wait. That didn't come out right.
This happy accident reminds me of the techniques James Randi has so often used on people with alleged supernatural abilities. I'm re-reading his classic Flim-Flam!, which contains a number of examples. When, for instance, a woman said she could use dowsing to find ancient ruins just by examining a map, without even a scale or North-pointer, Randi tested her on three maps in sequence, all of which were actually of the same well-explored part of Peru, but rotated and scaled differently.
Needless to say, her exceedingly vague results put "ruins" in different places every time, and not a one of 'em even managed to hit Machu Picchu, which was exactly the sort of thing she said she could find.
(Audiophiles usually seem to address psychoacoustic problems by adding as many more uncontrolled variables to their sound comparisons as they can. I presume this is some sort of demonstration that their perception of sound is not merely superhuman, but super-mega-ultra-hyper-human.)