As a follow-up to my earlier post on how music companies should be selling (and we should be listening to) higher resolution, uncompressed recordings, CDM recently mentioned Korg's brand-new one-bit recorders. It sounds silly, but basically instead of running a set of filters to get a full multi-byte description of the waveform's state, these sample the waveform millions of times a second, checking only to see if it has gone up or down. The advantage is that they don't require filtering for noise that results from the Nyquist theory, which states that sampling may produce sine-wave artifacts at frequencies higher than 1/2 the sampling rate (thus the reason that CDs are set at 44.1KHz rates, which is slightly more than twice the 22KHz boundary of most human hearing). Instead, a one-bit digital-analog conversion is turned straight into voltage changes, for a theoretically cleaner sound--although they are vulnerable to extremely high frequency noise, well past the limits of perception but enough to mess with some older equipment.
Korg has a nice intro paper online to explain this in a little more detail, and to give context: they're basically selling these recorders as ways to hold onto mastered content in a completely lossless format. Sound on Sound reviewed the units in this month's issue, and they were impressed with them, although the mic preamps are apparently weak. I'm also unclear on why they're selling one of these in an iPod-style form factor, but I'm strangely tempted by them. Apparently you can get a whole 22 minutes of incredibly faithful audio per gigabyte of storage with one of these. I feel more exclusive just thinking about it.