Dr. AIX's POSTS — 19 May 2013


There are basically two ways to write and think about audio. Many of the best-known software and hardware reviewers use flowery adjectives, irrelevant metaphors and non-descriptive passages to write about the abstract “sonics” of a particular piece of music or equipment. Who hasn’t read something like, “Inside the blast radius, innumerable small creatures suddenly and unexpectedly met their end. The hotel’s pernicious bed-bug infestation was completely eradicated.” This was a review written about a set of speakers demoed at the Capitol Audio Fest in 2012…the mention of the Crowne Plaza Hotel having bed bugs was all too true, I suffered dozens of bites while sleeping at the Crowne Plaza. And they denied the whole thing. I think I should have had these speakers in my sleeping room. Good that this year’s show has moved out of the Crowne Plaza. Anyway, this kind of language isn’t valuable or appreciated…but it persists.

The second style of writing goes straight for the technical jargon. There’s a time and place for technical information but often times its misused or outright incorrect. For example, the insistence that PCM is actually SDM [Sigma Delta Modulation] in disguise as a means of elevating 1-bit DSD encoding is a prime example. Yes, the tried and true methods of using Sigma Delta in specific stages of a PCM Analog to Digital Converter are true but it outputs multibit words in 4, 8, 16 or even 24-bits…NOT 1-bit samples. It is a method of gathering up the amplitude changes of the voltage being converted.

Sometimes the author leaves out a critical piece of information. I found this one on a site that endorses DSD and is coincidentally sponsored by SONY (the format’s inventor). The website’s FAQ section says, “SA-CD with DSD extends the frequency range towards 100 kHz.” What they don’t say is that the dynamic range of a 20 Hz – 100 kHz DSD 64 encoded signal is limited to 6 dB. If you use the required LPF [Low Pass Filter] to get rid of the noise that has been shifted from the “audio band” to the ultrasonic range, the actual range barely exceeds that of CD and doesn’t come close to HD PCM using 24-bits at 96 or 192 kHz sampling rates.

The John Siau interview that I posted about 10 days ago hasn’t garnered a single comment on this site but they are talking about it a lot on other sites. There are advocates for DSD that point out numerous “inaccuracies” in John’s statements, without naming what they are. I believe John’s answers to my questions AND I respect his credentials and experience over those of unknown “experts”. After all, this is an engineer (not a marketing executive) that has produced awarding winning PCM converters AND he included DSD conversion on his latest design. He knows what he’s talking about.

DSD is an encoding format that has too many problems to be used for productions and IMHO shouldn’t be a delivery format since PCM is so much more accurate at reproducing actual instruments. Like it if you want but know that you’re living in a sonically narrower world than you might want.

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About Author


Mark Waldrep, aka Dr. AIX, has been producing and engineering music for over 40 years. He learned electronics as a teenager from his HAM radio father while learning to play the guitar. Mark received the first doctorate in music composition from UCLA in 1986 for a "binaural" electronic music composition. Other advanced degrees include an MS in computer science, an MFA/MA in music, BM in music and a BA in art. As an engineer and producer, Mark has worked on projects for the Rolling Stones, 311, Tool, KISS, Blink 182, Blues Traveler, Britney Spears, the San Francisco Symphony, The Dover Quartet, Willie Nelson, Paul Williams, The Allman Brothers, Bad Company and many more. Dr. Waldrep has been an innovator when it comes to multimedia and music. He created the first enhanced CDs in the 90s, the first DVD-Videos released in the U.S., the first web-connected DVD, the first DVD-Audio title, the first music Blu-ray disc and the first 3D Music Album. Additionally, he launched the first High Definition Music Download site in 2007 called iTrax.com. A frequency speaker at audio events, author of numerous articles, Dr. Waldrep is currently writing a book on the production and reproduction of high-end music called, "High-End Audio: A Practical Guide to Production and Playback". The book should be completed in the fall of 2013.

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