Dr. AIX's POSTS — 26 June 2013


There have been lots of attempts by audiophile hardware and software companies to try and market improvements to the 44.1 kHz/16-bit restrictions of the Redbook specification. The folks at JVC created something called XRCD. Did it possess better fidelity than a standard CD? No. The mastering process and specifications of the replicated discs might have been done with greater care but the CD themselves were still 44.1/16.

Mobile Fidelity came out with a line of CD that used gold instead of aluminum to reflect back the laser light coming from the pickup in CD players. Did that improve the sound or fidelity of their releases? No. Will the gold CDs last longer than a standard aluminum sputtered CD…perhaps. It might add another 25 years to the 50-75 years that CDs are expected to last.

I read about a Japanese company that was selling limited edition glass CDs (these are individually cut by a laser beam recorder in the same fashion as the masters used to make stampers through a plating process). The company was charging $800 each for these “ultimate quality” CDs. Did they produce any better sound then a standard CD. No.

There have been K2 Mastered CDs, High-Resolution CDs and other fancy marketing names attached to the same Redbook specification compact discs for years. The HDTT (High Definition Tape Transfers) website would have you believe that recordable CDs made by Taiyo Yuden produce better sound than replicated ones. Not true. In fact, the error rates produced by recordable CDs are more than carefully replicated CDs because the reflectivity of CD-Rs is less than the aluminum sputtered discs. Why push that agenda…so they don’t have to go to expense of replication. CD-Rs can be made to order.

Here’s my favorite from a site I visited today, “DXD is digital PCM format using 24-bit signal sampled at 352.8kHz. No, it can’t be at present released on any medium, but that is how the material from master tapes is saved on a hard drive during mastering and in this form it is processed. Than (sic) the signal is downsampled to 16-bit, 44.1 kHz. By shaping noise and using adequate dithering (an intentionally applied form of noise, used to randomize quantization error) they manage to achieve 20-bit resolution on CD!” [NOTE: I don’t really get the “from master tapes” part of the statement…that would make DXD completely meaningless…oh well!]

So what am I supposed to believe? An uniformed person reading this statement might believe that someone has magically added 4 bits of resolution to a Redbook CD. If they did it wouldn’t be a Redbook CD anymore! The reason we have standards is to ensure that everyone that signs on to that standard produces hardware or content that will reliably play according to that standard. In my experience producing DVDs and Blu-ray titles is tough enough even if you do follow the specifications…it seems like there are always problems with a few machines.

There is an immutable fact about compact discs that cannot be changed by wishing, marketing or techno babble. CDs use PCM encoded audio at 44.1 kHz sampling rate with 16-bit linear words. This is a box that defines the maximum “potential” fidelity of a compact disc, which can be absolutely wonderful. But it’s not possible to exceed that specification.

Be wary of anyone promoting 20-bit CDs or anything else that supposedly improves the quality of compact discs. If you feel you must do something, just get you green magic marker out…that all the “magic” you’ll ever get.

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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.

(6) Readers Comments

  1. Dear Dr Aix, I take some issue with the statement you make, “An uniformed person reading this statement might believe that someone has magically added 4 bits of resolution to a Redbook CD. ”

    I personally have seen non-uniformed personnel make this same mistake.

    • Barry…you’re absolutely right. I was trying give people an escape hatch.

  2. Hi Barry

    I am one of those uninformed people, however I have a copy of one of these 20bit claimed CD’s with Super bit mapping technology,l from Sony classical, artist Bruno Walter, Beethoven Symphony No.4.

    I cannot help but to notice a huge difference in clarity, better stereo image and excellent frequency response compared to other CD’s. Not to refute what you is explained here-in as per article and your attest to it. My question then is, how do you explain the improved musical experience i have with this recording?

    I also have another CD that seem to be gold coated and music play back from those source is much better that standard alluminium coated CD’s. I usualy play these recordings on a non-high end car stereo however I can readily notice a difference. Your input will be appreciated.

    • The HDCD process is a valid technique for getting higher fidelity out of a 16-bit media. But there is no difference at all between a gold CD and one replicated using aluminum…in terms of sound quality.

  3. Just to say that I’ve encountered significative differences in sound with 20 bit super bit mapping cd’s, compared with exactly the same album in the standard cd edition. Better sound in general, more space and detail, everything is more clear and closer.
    Albums: Pink Floyd – Wish You Were Here, Billy Joel – 52nd Street
    Gear: Marantz CD52 MKII, Yamaha CX-1 preamp, MX-2 power amp, Van Den Hul The Source ‘hybrid’ RCA (single ended) interconnects, Yamaha NS-1000M speaker system and/or Fostex T20 headphones.

    • I believe you. But the differences are not the result of the additional bits…it’s because they went through different processes to get to your ears.

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