Not So Bit Perfect About DSD vs. PCM?
Richard at BitPerfect wrote a rather long piece on his blog and FB page called “On DSD vs. PCM…Again”, You can read it by clicking here. The catalyst for his 8000-word post was a couple of posts that I wrote about the DSD 64 vs. 96 kHz/24-bit PCM debate. You might recall that a reader over at Computer Audiophile ripped my entire post and posted it over at Chris Connaker’s site. Over the next few days, the CA community contributed 530 (it’s probably more now…I’ve dared to venture back there) comments trying to refute my contention that 96 kHz 24-bit PCM audio produces more fidelity than DSD 64.
He called me out in his article…challenging my knowledge of the “facts” and referring to my stance as “almost a point of theology”. I read his piece a few times and much of it just didn’t pass the smell test. In the first few paragraphs, he acknowledges, “technically, what he says is correct.” And then he goes on in paragraph after paragraph explaining the technical reasons why DSD tops 96 kHz/24-bit PCM.
So I sent the link along to the smartest guy I know in this regard and asked him whether my hackles were justifiably raised. Enter my good friend John Siau, a fellow PCM advocate, analog and digital expert, and principal of Benchmark Digital. I think his expertise and thoughtful responses are worthy of posting…with his permission so I’m going to spend a few posts talking about Richard’s piece, my thoughts, and John’s comments.
BitPerfect: “Another ‘fact’ is, though, that much to Waldrep’s chagrin, there is a substantial body of opinion out there that would prefer to listen to DSD over 24/96. Why should this be, given that the above technical arguments (and others that you could also add into the mix with which I might also tend to agree) evidently set forth ‘the facts’? Yes, why indeed…and the answer is simple to state, but complex in scope. The main reason is that the pro-PCM arguments conveniently ignore the most critical aspect that differentiates the sound quality, which is the business of getting the audio signal into the PCM format in the first place. Let’s take a look at that.”
John Siau This anecdotal evidence is meaningless. Very few people (if any) have ever had the opportunity to compare identical recordings delivered on PCM and DSD. There are many wonderful sounding DSD recordings that are being produced by highly skilled recording engineers who are putting a high emphasis on quality. The wonderful recordings that they are producing are a reflection of the care and skill that they put into the recording and production process. The quality is not due to the DSD delivery format. Based upon the mathematics, a 96/24 PCM dub of the DSD should be indistinguishable from the DSD original. This comparison would yield meaningful data. Anecdotal accounts of DSD sounding better than PCM are meaningless unless the same exact recording is available in both formats.
I’m not sure I understand why Richard uses quotes around the word “facts”…everything I stated in my post is true. I have no problem acknowledging that certain forces within the high-end audiophile community have succeeded in hyping DSD to the point where many make the claim that DSD is “warmer” or “more like analog”. They are certainly entitled to their opinion…just as one of the most prominent DSD supporters claimed on a panel at the Newport Show that with DSD “their is sort of an ease, a naturalness, roundness that I associate more with analog than I do with digital.” His opinions can’t be supported with facts.
I wrote a post about a German research project that compared DSD vs. PCM. The team recorded selections of music with exactly the same signal path and at the same level. You can read the post by clicking here. Here’s what they stated:
“The results showed that hardly any of the subjects could make a reproducible distinction between the two encoding systems. Hence it may be concluded that no significant differences are audible.”
But still audiophiles, writers, engineers, producers, and editors continue to insist that DSD rules.
BitPerfect: “If we are to encode an audio signal in PCM format, the most obvious way to approach the problem is using a sample-and hold circuit. This circuit looks at the incoming waveform, grabs hold of it at one specific instant, and ‘holds’ that value for the remainder of the sampling period. By ‘holding’ the signal, what we are doing is zeroing in on the value that we actually want to measure long enough to actually measure it.”
John Siau This entire discussion is irrelevant. It is a giant detour. Why take a tour of all of the A/D techniques that are rarely used for audio?
No one is using “sample and hold” methods any more! Anyone who has watched Monty’s video over at the xiph.com site knows, the values output by a current high-end ADC aren’t “held” between samples. There are no stair steps in analog to digital conversion.
Let’s stop here for today. And thanks to John for taking the time to read this article and response when Richard veers from the “facts”.
I’ve said it before and I’ll say it again: What the DSD advocates are referring to as “warmth” is the sound of the low-pass filter DSD needs to have set at a lower frequency than PCM’s Nyquist frequency, in order to block the high-frequency square waves that DSD creates.
It’s all those pesky high frequency overtones that they hate, which makes the music sound bright, instead of “warm.”
The story is that baby ducks “imprint” on the first creature they see and follow it around as their mother.
This bunch of quacks have imprinted on overtone-starved recordings – and consider anything else as sounding “cold.”
They don’t openly say that they think MP3s sound better than CDs, but that’s only to avoid blowing their elitist credibility. After all, MP3s also have reduced high frequency details – which is how they can squeeze files so small.
I will keep it short today. We all understand the value of specifications, but hopefully we also know that we don’t hear specs, numbers, etc. We can’t taste the wine by the label either. Much of what you write is ‘factually’ true.
I would simply say that there is a very thin line between the mathematical ‘facts’ and the perceptions of many qualified listeners, studio folks, musicians, etc. . I’m not into the Emperor’s clothes by any means, but when enough people w/ excellent work records, ethics and significant accomplishment all say the same thing, this certainly begins to look as ‘factually’ valid as a bunch of specs. I do have to agree with the statement that you do sometimes sound theologian. I went to a top 10 college, yet I was amazed when a tenured professor said to me,” I’m paid to teach, not to learn. ” Sometimes it kind of sounds like that in this column.
You can’t make great sounding recordings if the basic specifications aren’t met.
“Much of what I write is ‘factually’ true?” I report Craig…I don’t make stuff up and if there’s something that I don’t know I ask experts. I’m thrilled that John was able to shed some light on the piece by Richard at BitPefect. He challenged my assertions very hard…and over the next few posts, you’ll see why his claims are not on the mark. The marketing spin that has accompanied DSD has been masterfully done. It’s been shown that the same audio in DSD vs. PCM is indistinguishable…live with it. The talent of the engineers and producers eclipses the format anyway.
I’m here to report, share my knowledge…and to learn. I learned a lot today thanks to any expert like John. Hopefully, you’re learning a few things too.
You bet, and I always appreciate it mark. Have a great 4th. The local fireworks here occur right over my driveway, Considering the infinite air mass, those puppies sure couple up well enough to really POP our ears!
We enjoy the fireworks at the HS down the street and up along the coast towards Malibu from our living room. Charlie will be fine. Happy Holiday!
I must say I find it hysterical that he would accuse you of being almost theological about PCM. In fact, it is the DSD advocates that are the ones that show the most religious fervor. Personally, I want to format of the original recording. tf it is all DSD, that is what I want. If it was a DSD recording that was mixed and/or edited in PCM, I’ll take the PCM.
Thanks Joe…there are very few native DSD recordings. However, it the content you want is only available on SACD or as a DSD file then you have no choice.
In all comparisons I’m aware of the average Joe hasn’t been able to reliably distinguish between high rate MP3s, CDs, and something like 24/96 PCM so I’m highly doubtful of people really being able to distinguish between PCM and DSD
But if the DSD side is right and it’s sounds warmer, more analog like. What they’re hearing and liking is the same distortions and inadequacies of analog/vinyl. As Phil mentioned above, those are the measurable inadequacies and distortions of the frequency extremes.
It is very challenging to perceive differences between formats…even lossy ones.
Goodbye Yellow Brick Road by Elton John was one source mastered in both DSD and PCM (SACD and DVD-A).
I went to a seminar a while ago and met the engineered and remixed this in surround, Greg Penny. I know this was originally an analogue multi-track recording, but it sounds amazing and should be a good test for both formats. I don’t remember which Penny preferred (I think he said he liked the SACD better, but I am not sure.) but I think the differences people might be perceiving might be the result of the DACs being used, especially if people are comparing by playing one in a SACD player and the other in a DVD-A player. But I am curious what you think playing these discs, and comparing it also to the newly released Bluray Audio disc of this album. It would make an interesting comparison.
I met Greg Penny years ago and love the Elton John project. The surround mix is really good. I prefer not to get into the format debate between DSD and PCM on an album by album basis. DSD is never going to be a major format in the record industry because of its numerous shortcomings. It does keep a lot of people busy talking about it though.
Hi Mark – Monty’s video is at xiph.org not xiph.com.
You’re absolutely right…sorry.
Geez Mark, I’ve learned a lot reading your daily posts. Enough to frazzle my tired old brain. I supported DSD somewhat, when I got my Oppo, because I could put it in and play it. The few DVD-As I have or borrowed involved turning on the TV to set them up. I just read somewhere that with Blu-ray, and maybe [I don’t know] DVD-A, I can bypass the monitor using those colored buttons on my remote. The ones I never bothered to learn about.
I was looking in to streaming to a new dac, and found out my PC doesn’t have, or will accept enough memory for USB 2. I’m a dinosaur.
Anyway, what today’s post got me to thinking. We all seem to debate, or worship one format over the other, while never considering how the data got to that file, or in my case disc. What type and quality of analog to digital converter is being used? My friend has a little home studio business. Not a very successful one, and these days for good reason. His PC is running Windows 98. His ADC is just as old, and no nice old reel to reel, to at least get a good master. All outdated digital gear.
So I have to hope that when old analog tapes are being digitized for sale and/or archived, they are using the best equipment available. If CD transports, digital cables, and dacs can all sound different, then ADCs must all have some sound of their own. I do understand that in a perfect world, and just based on the digital science bits would be bits. Our ears tell us different, we know that power supplies, discrete or op amps, or tubes all effect what we hear. The above goes for modern digital recordings too.
Have you in the past written about the analog to digital process. Every recording, unless it is some weird electronic music starts with analog mics and instruments. Is that what is causing much of the current debates?
Very good points Jeff…although I still have a functioning Windows 98 machine myself. Who’s the dinosaur? Unfortunately, not very many mastering houses are using the absolute best analog to digital methods or machines. Fred Thal, a master of analog tape decks, made that point in a recent post…he redoes Studer decks but doesn’t get many sales from the people that should be using his stuff. The ADC process is a critical stage just as the DAC stage is. I don’t recall addressing the exact AD conversion process…good idea.
I would appreciate some thoughts (and facts) from you, Mark about this too.
It is a very important theme.
I was going to chime in on John’s corrections…but his expertise is far beyond my own on the technical merits of DSD.