Dr. AIX's POSTS — 18 September 2013

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Here’s a quote from Paul McGowan, the owner and senior desiger at PS Audio, that he posted the other day on his daily blog. “PCM is on its way out. The very language that started the digital audio resolution is going the way of Esperanto.” As you might expect, I was surprised to learn this and actually wrote a quick response to his comment during my office hour yesterday at the university. My comment was about the realities of the professional production facilities and the standard practice of audio engineers making the audio played back through digital to analog converters. We’re ALL working in PCM.

Paul responded, “Boy, then you’ll love tomorrow’s post. I agree with you in part – as I will mention in tomorrow’s post, PCM is the majority carrier of music and storage of that music, editing and manipulation and will be for some time to come – having said that, most of us are converting from PCM to DSD in our DACS (and not knowing that).

That notwithstanding, I believe the future of all digital REPRODUCTION will be via DSD based Delta Sigma DACS. Storage will be via PCM as you suggest.”

Okay, so Paul acknowledges that the audio world is going to stay with PCM for the production of new recordings. He’s right. That’s where the tools are and that’s what the production world knows. But we’re going to be converting the PCM digital audio back to analog using DACs that have a Delta Sigma processing stage in them. He calls this “DSD based”. Most engineers wouldn’t…they’re still PCM DACs.

I have to wonder about whom the “most of us” that Paul is talking about in the second paragraph. Is he referring to the equipment designers that are including DSD in their “new and improved” DACs? These are guys like John Siau of Benchmark and Mike Moffat, formerly of Theta Digital. Both of these very experienced designers know the shortcomings of DSD and have publicly expressed their opinions on the topic. But there companies have actually included DSD conversion in their latest designs. However, if you ask them why they did it, they will tell you because there is money to be made from consumers that perceive DSD as being superior to PCM. Give the customers what they want…and they did. That statement may be true for those consumers that like SACDs but it is not universally true. I’ve gotten lots of email from consumers that have heard SACDs for years and still prefer PCM.

Then again, Paul might be saying that because modern DACs now include advanced integrated circuits that have some sort of multi-bit, very high sampling rate, Delta Sigma stage (not officially DSD, which remember is limited to 1-bit) prior to the decimation back to usable output of PCM audio 24-bits long…that DSD is taking over the world of high-end audio. That’s like saying that because there is a battery in all automobiles that electricity is overtaking gasoline-operated cars. Come on.

I’m not an equipment designer. I know enough about electronics and digital theory to be dangerous but I don’t pretend to be able to speak with authority on the intricacies of the latest converter chips. However, I can read a schematic, repair most analog electronics and I do understand when someone is speaking out of the corner of his or her mouth.

PCM is most definitely not on the way out…as Paul acknowledges in his response. He said it because he knew it would generate controversy and comments on the PS Audio blog page. He’s a smart marketer.

He is an advocate of the PDM model for encoding of audio. I’m not. The facts as I have studied them simply don’t add up…but we’ve already talked about that. I won’t be using DSD to record any of my pristine recordings. I am considering doing what Benchmark and Schiit Audio have done and “give the customers what they want”. I might make DSD versions of my own stereo HD-Audio PCM masters available on iTrax.com.

What Paul is saying is that the use of a Delta Sigma component in modern DACs somehow transforms ALL audio that goes through that component (which is DSD like but definitely not DSD) into DSD. This is marketing speak and deliberately vague. And not true.

Fans of DSD get encouraged by statements like that and those of us that prefer the science and sound of PCM can accept it as marginally true as long as we know that modern DACs are still going to take PCM encoded audio in one end and put high-quality analog audio out at the other end. What goes on in the box could be a flux capacitor for all I care.

Future productions, mastering, encoding and distribution will be dominated by PCM audio for a very, very long time. Count on it.

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About Author

Dr. AIX

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.

(5) Readers Comments

  1. But, if we are “converting from PCM to DSD in our DACs”, are we also encountering the noise shifting issues that you have described with DSD?

    • Any conversion to the 1-bit world of DSD will result in the ultrasonics being full of HF noise. There’s no getting around it. The DSD folks are moving to 5.6 and even 11.2 MHz to get move noise free room in the 20-40 kHz range, but the noise is still there just shifter every higher.

  2. Pingback: DSD - (Don't Stream Digital) - Page 3

  3. Hi Mark,
    Interestingly, the latest Sony High Resolution Audio (HRA) products – http://discover.store.sony.com/High-Resolution-Audio/ – does exactly that : convert all PCM flux into DSD 5.6 MHz before converting to analog by means of an analog low pass filter. One can read the following lines in the Sony web pages :

    This ideal D/A conversion system combines a high-performance DSP and FPGA (field programmable gate array) to convert all signals to 128 FS DSD signals. It was designed based on know-how garnered from Sony’s direct 8-times oversampling and Extended SBM (Super Bit Mapping) technology for professional recorders.

    It’s time to surrender, DSD is creeping everywhere by now… 😉

  4. I would think of the processing being promoted by SONY on their new hardware as similar to any “timbral” modification process available on various pieces of equipment. It’s certainly possible and even likely that advocates of the “sound” or DSD are responding positively to the distortions and HF noise that is inherent in the format. It would just like me sending my pristine masters through an “analog tape” processor that would make them sound like analog tape.

    I can’t imagine that everyone would want to downgrade the accuracy of a great recordings to “analog tape” or DSD 128 just for the “enhancement” that they like but stranger things are happening in our hobby. So more power to Sony for offering equipment that converts everything to DSD.

    There is no need to surrender anything. If DSD turns you on, then keep purchasing DSD. But realize that only 16% of all SACD (and thus the DSD files they contain) are actually natively DSD…the rest came from analog tape or PCM masters.

    DSD is a niche format and will remain a niche as far as I can see.

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