CHUCK@umiami.miami.edu (Charles J. Urwiler) (02/21/90)
Hello folx. I was thumbing through all of the old postings here and I noticed some discussion about 1-bit machines. Well, we just happened to finish discussing them in my Digital Audio class here and I thought I'd share a little of what I learned. First of all, these 1-bit doohickeys are only for the output stages at the present time. As another person noted, CD's are recorded in 16-bit, and there is obviously no way to change that. All that these 1-bit's do is take those 16-bits and crunch them down to 1 bit toggling on and off at very high rates - on the order of 11 MHz to 45 MHz. I have a chart (it was complied by JVC) on some of the different 1-bit architechures out there. There's Philips, Matsushita, JVC, and Sony systems on this chart. The Philips system uses Pulse Density Modulation at the output, while the Matsushita uses Pulse Width Modulation. The JVC and the Sony use proprietary Pulse Modulation systems, but they are basically PDM. They each have their own noise-shaping algorithms, but are of at least 2nd order. Linearity of these 1-bit systems is amazing, in my opinion. A 16-bit system gets into non-linearities at -80db or so, while 1-bit systems are good till -100db or more. Big difference! We're finally achieving the point where differences in the new systems are gonna be inaudible. Another advantage: cost. The 1-bit systems are cheaper to make. Therefore, you should see these babys around for years to come. One thing someone stated is storing this data. I'm sure it's possible but right now I think the R&D went into the A/D conversion step, basically for CD purposes. Again, look for the advancement of this conversion process! It's really hot and actually, very complex. For some reading, check out _Mix_ magazine, February 1990 issue. Ken Pohlmann's column "Insider Audio" talks about 1-bit systems. -- =========================================================================== Chuck Urwiler University of Miami Music Engineering Voice & Keys chuck@umiami <<BITNET ADDRESS chuck@umiami.miami.edu <<INTERNET ADDRESS =========================================================================== Disclaimer: I only work and learn at this University. I don't speak for it!