Coming to a CD Player Near You?
February 9, 2007
Early in 2006 I received a CD-R from a fellow named Stefan Pudritzki. Doug Schneider had received this same CD-R and asked Stefan to send me a copy. The disc contained pieces of music burned directly from the CDs on which they appeared along with versions of the same music that Stefan resampled with a digital filter he developed. Called PentaDelta, Stefan's filter was designed to reduce the quantization noise of digital samples and interpolate between samples when increasing the sampling rate. "I developed it on a Milan 040 computer system, which is compatible to the Atari ST computer, with a Startrack soundcard using a Motorola DSP56002 and several programs which I developed on my own." The sonic effect of Stefan's PentaDelta filtering was obvious: Digital music sounded more like very good analog. It had warmth and smoothness along with all of the detail of the original pieces. The sound was more relaxed, much like that of a JVC XRCD.
A few weeks ago, Stefan wrote me to say that he had improved upon his PentaDelta filter, which produced "too much distortion on upsampling with a quotient of sampling rates that is a non-integer value." The new filter, called TriDelta, detects and reduces quantization noise, then interpolates, reducing output at 20kHz by approximately 1.2dB. "The result is an extraordinarily pure sound which will not stress your ears." Stefan sent me a DVD of cuts upsampled from 16 bits/44.1kHz to 24 bits/96kHz, and, once again, the results were easily audible.
Stefan is shooting for an OEM future for his TriDelta filter: "Because there are billions of CDs in the world, the best way to provide the new sound quality to the consumer is to implement my formula in new external D/A converters or in the D/A converters of new CD players." Of course, this is a big step, but given the performance-driven nature of high-end audio, I won't be at all surprised to come across a CD player or DAC that uses Stefan's TriDelta filter at a future CES....Marc Mickelson, firstname.lastname@example.org
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