Dr. AIX's POSTS — 01 August 2014


The Redbook specification rules everything to do with compact discs. It established the physical attributes, the electrical requirements and the data protocols. It defines the audio as PCM at 44.1 kHz sample rate and 16-bit linear words…giving 22.050 kHz as the Nyquist or maximum allowable frequency and 96 (the theoretical limits for dynamic range…the actual is 93 dB due to dither). However, it doesn’t say anything about how the digital data is prepared prior to mastering OR that you must use polycarbonate as the material in the disc.

So if there is greater value associated with a CD release mastered by Steve Hoffman or one that is burned or replicated on a Gold sputtered disc then perhaps the higher prices charged for these discs might be reasonable. But to think that the fidelity will be inherently better on one of these specialized “flavors” is ridiculous. All you can get out of 44.1 kHz/16-bits is established by the final encoding format.

A K2 CD is prepared using a process that raises the sample rate and word length during the pre-mastering process. Let’s say you wanted a Chet Baker K2 CD made from the best analog tape you could find. During the transfer to PCM digital, the K2 HD pre-mastering system comes into play. The engineers use a more rigorous process, some juiced up equipment with higher sample rates and longer words and then master a really good CD…but it’s still a CD. So the advertising/marketing claims of “100 kHz bandwidth and 24-bit high-resolution” information on a CD are completely false. If a K2 HD CD did actually deliver those kinds of specs it wouldn’t be a compact disc anymore because it didn’t follow the specification.

Here’s the graphic that describes the K2 HD process:


Figure 1 – A promotional piece about the K2 HD Mastering Process.

I certainly endorse and even applaud doing the very best mastering job with the very best equipment available but have to drawn the line when the marketing and promotions people get into the act. Someone would have to show me how you can get 100 kHz of bandwidth and 24-bit high-resolution information on a CD…it’s impossible. But consumers read a bunch of positive testimonials or audiophile magazines give the process a thumbs up and consumers begin to believe that FIM has figured out how to squeeze more fidelity out of CD than Sony or Phillips, the people that invented the format. Save your money.

The same thinking applies to the rest of the “premium CD” flavors that are advertised around the web. I’ve written about XRCDs previously (click here to read my post) so I won’t spend more time and more words repeating myself here. These are very good CDs but any improvement in their sound comes from the mastering or better sources…not some special treatment during the replication. Again, save your money.

The last item on the list did catch my attention. This was a new one to me…the DXD CD, which makes about as much sense as designing and selling a new DAC with 768 kHz and 48-bit fidelity…and then playing CDs through it…or building it at all. Here’s the promotional line from the Australian website:

“Digital eXtreme Definition (DXD) is an audio encoding scheme that was developed for editing high-resolution recordings because DSD, the audio standard used on Super Audio CD is not ideally suited for editing. DXD is a PCM-like signal with 24-bit resolution sampled at 352.8 kHz – eight times 44.1 kHz, the sampling frequency of Red Book CD. The data rate is 11.2896 Mbit/s – four times that of DSD!

FIM/LIM DXD CDs have taken this a step further to bring you closer to the source. Instead of making two or more sample rate conversions as with SACD, FIM/LIM recorded the source in DXD! The data rate for a DXD mono signal is 8467.2MHz, or more than 3X the data rate of a typical SACD! Experience the closest you can get to the original performance in the comfort of your home!”

“Super High Definition format: Digital eXtreme Definition 24-bit 352.8kHz CD! Playable on all CD players!”

If it’s playable on “all CD Players”, then it doesn’t have 352.8 kHz or 24-bits!

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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.

(23) Readers Comments

  1. When is a CD not a CD?

    In the mid 90s, the Eagles released a CD with a DTS track. I never heard it. I assume that it took advantage of specifications for the data CD.

    • DTS did have an entertainment wing once upon a time called appropriately enough DTS Entertainment. And they produced and released a bunch of CDs that contained data (DTS encoded 5.1 surround mixes). They were not CD-Audio or Redbook discs and they posted warnings on them to alert consumers not to try and play the data through a stereo system. You had to connect the digital out to your A/V receiver and then the DTS decoding would kick in.

  2. Mark, I really enjoy taking in your information. As for the non-negotiable limits of CD, nothing to say that hasn’t been said. But again, some CD’s have characteristics that come closer to master tape sound than others, most notably K2 and XRCD. As for somehow exceeding the Nyquist limits, I hear you. However, this brings up the question of why no HDCD anymore. That process spoke of hiding extra information in redundant and parity bits which would be outputted when the HDCD chip recognized the”flag” that identified these discs. As with all formats, quality varies, but the best HDCD’s I’ve heard easily rival the K2 and XRCD efforts w/ noticeably increased bandwidth, clarity and dynamics. Yes, I know the associated digital filter is a negative on regular CDs, which is why the players that still have it (my Cambridge BD-752, better analog sound than Oppo), allow you to turn the HDCD decoding on and off. Regular CD does indeed sound better when HDCD decoding is turned off, but if all CDs had been good HDCDs’ there might have been absolutely no need for any higher fidelity for all practical purposes. Note; Any disc that Steve Hoffman has mastered is worth every penny charged IMHO. Best, Craig

    • Craig…it’s not that “some CD’s have characteristics that come closer to master tape sound than others”, it’s that they were prepared from better sources and mastered more carefully than others. If I took the same analog master tape and prepared a CD without K2 or XRCD, I would get the exact same fidelity as they do…because I’m good at it. Their technology was/is all smoke and mirrors. Now HDCD did actually enhance the actual specs…not a lot but some.

      Steve Hoffman does a really great job…however, when he endorsed a rebuilt Technics reel to reel as the best thing since sliced bread…he lost points with me.

      • I too greatly admire Steve Hoffman’s work. He does seem to have a preference for vintage gear. It’s like the worn wrench that the mechanic has been using forever; he has the ‘feel’ of it, and that’s why he prefers it to a new tool. I don’t care if he uses an am radio if he cranks out such fine work.

        • The studio here is full of vintage gear (Pultec, Echoplex, EMT plate reverb, Tektronics, UREI and much more). I would even count my Ampex 44C as a vintage deck…but a Technics RS-1500 is a consumer piece at best and can’t match a pro machine like ATR-100s or my Nagra IV-S.

  3. Is Blu-ray Audio the next big thing? I do like have a physical disc of my music but I grew up with LPs.
    They have a few of these discs on Amazon.


    • There are certainly people trying to make this happen…I have my doubts. Of course, I produced Blu-rays but they have full HD-Video on them as well. A straight “pure audio” blu-ray is a waste of time if the material isn’t real HD-Audio.

    • So far, Pure Audio Blu-ray gets my seal of approval. But…it cannot sound better than the original recording quality, of course. You will also need either a Cambridge BD-752(my preference,) or an OPPO 103 0r 105 to play back the hi-res through clean analog outputs. Otherwise you must use HDMI which takes you backwards sonically. HDMI audio has improved, but still not as smooth and natural as a analog. I too like a physical disc. One thing for sure, you don’t have to ‘back them up’ by purchasing two copies!

      • If you want to spend $30 for a Blu-ray of multiple encodes of the same standard resolution transfers that are available elsewhere for far less money, then more power to you. Pure Audio Blu-rays are for people that want physical discs and the benefits of simple operation. I sure don’t get the “HDMI taking you backwards” comment…it’s all about bits and converters and getting back to analog.

        • I have been designing systems and selling high-end audio gear for 32 years. At the dawn of “the cable wars,” I was there, and have unavoidably been involved with HDMI since it first came out.Do you know the real definition of HDMI? Try “H.ardly D.eveloped, M.ostly .Intermittent.” I have compared music through HDMI vs. good analog cables repeatedly over the years, and while HDMI has gotten much better, it is still edgy and artifact-y compared with the smoother, more natural sound that emerges from good analog audio cables. For most folks, auditioning HDMI comes attached to video, and the Craig’s 5th law comes into effect: ” When the eyes turn on, the ears turn off.” If you have never covered your eyes while watching/hearing a good concert video and heard what happens aurally, you should. Arcam has made HDMI sound better than any other outfit, and they will tell you about the 4250 picoseconds of audio jitter they have measured on average with an A/V stream through HDMI. If HDMI is the only way to hear a native DSD recording, then that’s just another reason to cock a suspicious eye at DSD, despite the popularity among the tweaky set of listeners. IMO, whomever cooked up HDMI should be shot; what an infernal connector, to say the very least!

          • A digital connection is a digital connection and unless there are reasons for problems (like distance or messed up sources), HDMI passes signal just as well as S/P DIF or AES-EBU. Any jitter in the signal is not a problem because a good DAC will reclock the samples.

  4. “it’s not that “some CD’s have characteristics that come closer to master tape sound than others”, it’s that they were prepared from better sources and mastered more carefully than others.”

    Isn’t that what K2 , XRCD, FIM et al are doing – getting better original source material and/or doing a better job of mastering? It may not be the technology that is resulting in the improvement but if the whole process does result in an improvement I am willing to pay extra for it and so are many of my clients. Sure – doubling the price is extortion but those who want the best are willing to pay for it.
    If you were to record, on your ” Ultra HD Audio” system, using crappy mics – the result would be crappy – right? Even so, CDs made from poor master tapes sound bad – not the fault of the master tape format be it analog or digital “Ultra HD”, but rather the poor quality of recording or mixing or mastering.
    Having heard analog multi track masters being mixed on location, I would be perfectly happy to have that level of quality reproduced in my listening room, even though it does not meet the criteria for Ultra HD Audio. Most consumers can’t handle even 60 dB of dynamic range in their listening environment.
    Question – is it ever the case that a “re-mastered” recording actually goes back to the original multi-track source?
    Or is it always the two track mix that is re-mastered?

    • My problem with the whole thing is calling it some special new technology, lying about the resolution and pretending that they’re doing something that everyone else can’t do. The sources that are available to one provider are the same as everyone else…and they’re usually not the correct master sources but some EQ’d master. Only very rarely do the multichannel tapes get revisited.

    • Dennis, we think pretty much alike. The very best two-track analog tape recorders were and still are fully capable of making recordings that I personally have no trouble calling hi-res. Sometimes I think Mark’s point of view is slightly biased by his business and techniques. As you say, poor mics or a bad-sounding acoustic environment will render the hi-res equipment issue a moot point. At any rate, no one, repeat, no one, can reasonably ask for anything better than a clone of the original master tape, or vanishingly close, no matter how or when it was made. Imagine hearing the first generation Robert Johnson blues recordings; I guarantee the hair would go up on anyone’s back!
      What would labels mean at that point? ZERO.

      • Craig, we’ve been through this before. I believe you would call the master of Robert Johnson a “high-resolution” audio experience. As far as asking for a clone of the original master tape, I can ask for more. How about an original master recording that doesn’t suffer from any degradation based on the format or the procedures used to make it?

  5. If jitter were not a problem, then high-end re-clocking devices would not serve their purpose. I don’t know if you have compared music delivery through high-grade analog cables and HDMI. I can guarantee it won’t sound the same .I am surprised that some one quite familiar with the fragility of the digital audio signal would reduce a complex situation to a simplistic analysis. Digital cables produce reflections of the digital signal which when re-introduced cause jitter, most digital cables are not true 75 ohm, Toslink sounds noticeably worse than coax in general, and on and on. The very fact that jitter as an audio problem is measured in picoseconds should cause one to sit up and take notice of the fact that it doesn’t take much to audibly degrade a digital signal…and on and on and on. Yes, DACS have gotten better, asynchronous, etc, but jitter is still the enemy in digital audio and HDMI has lots of it; think of the huge amount of two-way data in an HDMI stream; to think that jitter would not be a factor is patently hilarious. Thanks as always, Craig.

    • I didn’t say that jitter isn’t one of the prime issues that must be dealt with when passing around PCM digital audio. But I’m not sure I understand what you mean when you say that delivery through high-grade analog cables is much better than an HDMI signal to a converter to analog and so on. There has to be a conversion of digital to analog at some point. If you’re using high-grade analog cables, then you already converted. But the HDMI has yet to be converted at the DAC…then it’s back to high-grade analog cables. The actual transmission using good HDMI cables over a short distance to a re-clocking DAC does nothing to the digital signal. I go HDMI out to a Byrston SP-3 multichannel preamp and DAC routinely at trade shows and it’s spectacular. I prefer it over the analog outputs of the OPPO using the ESS Sabre DACs. I’m not with you on the fragility of digital audio. It’s actually more robust than analog signals and you really have to try to degrade it. Remember all we’re doing is successfully getting a bunch of data from one place to the other.

  6. Take a high-quality AVR such as Arcam. Run an HDMI feed from OPPO or Cambridge BD-752 to the AVR, and take whatever analog cables you like and simultaneously connect them from the player to the AVR, different input.. Put on a good-sounding disc, and switch back and forth. One, they won’t sound the same, and the difference is not all caused by the DAC differences. HDMI audio w/or w/out video sounds consistently edgier than the already converted analog feed, especially noticeable on voice .If you are defending HDMI as an audio carrier, I think you might be in the minority. And…after recent controlled testing here, anyone who says all HDMi cables are the same is either blind, deaf, or both. I wish this were not true, but the difference you can see and hear is not subtle. Thanks.

    • I can do exactly the test you claim results in “egdier” over HDMI. If I then take an capture both outputs through the same converter and swap the polarity and there is residual data leftover, you might have a point. I’m not one who subscribes to “analog” thinking when it comes to digital signals and connections. I’ve already done the testing with discs treated with “special sauce” and without…they were identical. Any differences come from the DACs and not the connection. We’re going to disagree on this one.

      • I really look at our discourse as a knowledge resource, definitely do not wish to pose as argumentative. Our experiences run parallel on some audio topics, and diverge on some others. This reminds me of one of the best sayings I’ve heard in years,” There are many paths to the same place.,” and I look at it that way, zero axe to grind. I am not an analog fetishist by any means. I’ve recorded using purist methods, produced both audiophile-grade LP’s and CD’s. If hamsters running the wheel made the best sound, I’d be a hamster guy!. Thanks Mark.

        • Craig…you’re among friends here. I appreciate a healthy challenge and don’t expect everyone to have the same perspectives on things. I want it to stay that way…I have no time for the endless rants over at AVS Forum.

          • Thanks Mark. Now, you were doing music before AV and know well that it has always stood on it’s own. No MTV needed for Beethoven’s music to be acclaimed. I fully understand the enjoyment factor of a really well done A+V experience. But I asked you this question before and did not get an answer. Have you ever taken in such a presentation for 10-15 minutes and then covered your eyes? The aural report changes dramatically; all the sound no longer seems to be coming from the screen, and a genuine soundstage emerges with more depth, dimension and flat out reality factor than the 5.1 or 7.1 AV architecture. To put it somewhat stupidly, it sounds like you are listening to music instead of concentration being lost due to the flickering video images. This is not a belief held solely by myself; many of my industry colleagues who love music have had the same experience. Your thoughts?

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