Monday, February 20, 2012

Another expert claims CD-ripping improves sound quality

Rev A (seen notes)

Additional searching to confirm Linn Hi Fi's statement that ripping CDs to computer memory improves the sound quality has so far turned up a lot of noise (i.e. ignoramuses babbling and Satanists practicing the art of deception in echo chambers knows as forums) and very little signal, the little bit of signal being a 2005 Postive Feedback article by Steve Nugent, a former electrical engineer and president of Empirical Audio (which has a page on computer audio).  The article goes into considerable detail about jitter, which is one of the sources of error involved in reading data from optical discs.

The article concludes by stating "Computer-driven audio is adding new life to the CD format, providing new methods to get even more performance from CD tracks. Those that have discovered the performance and ergonomics advantages of this new technology have found new joy in their music listening." In other words, on-the-fly error-correction of optical-disc players is not perfect, and the resulting errors are detrimental to sound quality.

Eliminating optical discs from the playback-chain is probably one of the major advances in digital audio since oversampling and the eventual transition to DVDs and SACDs, which made oversampling obsolete.  The main problem with oversampling, or interpolation, is trying to mathematically create high-res data using 16-bit data and formulas based on compromises. The result was a residue of artificiality which could not be eliminated because of the errors contained in the input data.

The idea behind interpolation is to increase the effective sampling rate at the output of the DAC, and make it possible to filter out undesirable high frequencies produced by sampling, without using steep filters which cause phase distortion. (Phase distortion causes the various harmonics of complex signals to become misaligned in time.) The earliest digital sounded "smeared" and lacked a sense of space because it used steep filters.  (When I saw the phase characteristics of the input filters of the earliest digital recorders, back in the late 70's, I remarked that they would cause problems, and was ridiculed by someone who had been assured by Sony that their product was perfect. We now know that Sony's "perfect sound forever" was half-baked, to put it mildly.)

The main problem is now piracy, and the recording industry has adopted various measures to combat it, including the use of certain secret "watermarking" techniques.

Notes
Rev A: Added comma in first sentence of next-to-last paragraph.  Was "...  to filter out undesirable high frequencies produced by sampling without using steep filters...."  Is " to filter out undesirable high frequencies produced by sampling, without using steep filters...."