Dr. AIX's POSTS — 02 October 2014


Yesterday, my post was a mini test. It consisted of 10 questions…a few True and False questions and a bunch of multiple choice questions. The students at the university would love to see me prepare a test full of multiple choice questions…but I required them to write out their answer. Consider yourselves lucky.

Here’s the answers:

Question 1: The correct answer is letter “B” or 60 dB. Analog tape machines are not very good at capturing dynamics.

Question 2: None of the formats listed in this question qualify as high-resolution. DSD 64 comes the closest but because of the excessive noise that exists in the ultrasonic frequency range, I leave it out. The correct answer is letter “E”.

Question 3: False. Analog recordings don’t gain dynamic range just because they’ve been transferred to a large digital bit bucket.

Questions 4: The correct answer is 4-bits or letter “D”. The mastering process used on commercial release reduces the overall dynamic range of virtually all CDs to less than 10-12 bits or less than 4-bits.

Question 5: The answer is letter “A”. The Dolby Digital or AC-3 encoding scheme is a lossy algorithm and therefore doesn’t reproduce all of the fidelity that was contained in the original source recording.

Question 6: The correct answer is “D”. If the substance that you use on your optical discs cleans the surface and is completely removed from the surface after use, then it might result in better transmission of data from the “pits” of the disc to the optical pickup. The rest of the items on the list were actually taken from published statements about these products, from magazine reviews, or from customer testimonials.

Question 7: False. This notion is very widely believed by analogophiles. It’s patently false. Both statements are false. We don’t measure analog system with terms like resolution AND there are no stair steps in a PCM digital recording when it’s converted back to analog (in fact the data isn’t stair steps either).

Question 8: False: Moving from 16-bits to 24-bits lowers the noise floor and provides a safer margin from overages and distortion for recording engineers during sessions.

Question 9: The correct answer is “E” or all of the above. Dither is a very useful technique for removing or masking quantization noise and spreading it across the entire frequency spectrum.

Question 10: False. Although this statement has been widely used on website and promotional brochures that advocate for DSD, the fact is that DSD 64 recordings or SACD have about the same specifications and fidelity as a standard CD.

So how did you do? I’m expecting to receive some push back from some of you on several of these questions. So go ahead and let’s discuss.

As for grading…here’s how I would score things:

9-10 correct deserves and A
8 correct earns a B
7 gets a C
6 out of 10 lets you squeak through with a D
and anything less means you fail.

I hope you enjoyed the Audiophile Midterm. Keep studying and we’ll have the final exam in a few months.

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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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