96kHz or bust

September 7, 2013
 by

While the hornets swarm around the last subject we brought up for a little bit, I thought perhaps we'd turn back to A/D Converters, the topic we started before all this got somewhat sidetracked. When we left off our discussion on the Analog to Digital Converter, I had just finished explaining the function of the Sample And Hold Circuit of older, more traditional A/D Converters. That circuitry used to take a "slice" or "snapshot" of the incoming analog signal, hold its value intact while the A/D Converter converts the sample to a digital number.

Early A/D converters needed the sample held because the method they used to figure out the correct digital number for the sample was time consuming. Many of the original Pro A/D Converters, used to record music, ran at 48kHz and were bandwidth limited to half that sample frequency, or 24kHz, just slightly above the extremes for human hearing. As you may remember, the system had to employ a steep and (mostly) intrusive filter on the input to make sure no higher frequency artifacts were sent to the A/D Converter, or a form of distortion known as Aliasing might occur.

Today's A/D's are much more sophisticated and fast, not suffering these types of distortions or limitations at all. For example, the A/D used in our upcoming NPC product has an incoming sample rate of 352.8kHz. To put that in perspective, it means we can have a very gentle low pass filter on the A/D Converter's input that starts at 80kHz, far outside the band of any usable audio information from any format other than perhaps a live performance (and then "useful" information might be questioned). In fact, we are recommending that NPC users do not exceed 96kHz for playback or recording of bandwidth limited analog source such as vinyl LP's, tape recorders, FM tuners, etc..

This recommendation no doubt flies in the face of many of us who would immediately go right to the highest available sample rate of 192kHz. I know I did before doing a little research and listening tests. But truth is, 96kHz not only sounds better when playing vinyl LP's, it makes no sense to go higher. There are several reasons for this: first, 96kHz/24 bits captures any and all info possible on a vinyl LP, tape recorder or just about any analog source you might connect to the A/D. Because the output sample rate on the A/D Converter is unrelated to the input sample rate and rolloff (352.8kHz and 80kHz respectively), there really isn't any downside to using 96kHz to feed your DAC or computer. One last reason (and this applies to many modern A/D Converters) the decimation digital filters (output digital filter) have guaranteed zero group delay only up to 96kHz. Beyond that most modern A/D Converters have some form of small group delay above a higher frequency. Group delay simply means that some groups of frequencies are slightly out of time with others and in the case of an A/D, it is a consistent gentle change at the upper frequencies. Audibly you might hear a slight emphasis in the upper frequencies, relative to a zero group delay. Recording engineers can (and do) make slight EQ adjustments to compensate when employing higher sample rates with PCM - but for mere mortals like us, we don't generally have such luxuries available.

I know this is going to raise the hair on some folks necks who are convinced that PCM running at 192kHz is essential for best sound, but I would have to argue that if you handle the incoming musical signals properly (i.e. do not roll them off anywhere near the usable bands) there really isn't much advantage to it UNLESS you are converting DSD to PCM. Standard rate DSD runs at 176.4kHz and double DSD runs at 352.8kHz. But if you are playing or recording vinyl LP's, tape recordings, FM tuners etc. there's no advantage to higher sample rates than good old 96kHz/24 bits. if you're recording live performance events using the A/D there may be some wisdom to capture using the highest sample rate and bit depth when properly executed, but if I were making live recordings I'd be using DSD and not PCM anyway (and none of these issues apply to DSD).

Perhaps a lot to absorb here, but it would seem to me a very common sense approach to making high resolution copies of your analog sources, saving hard drive space, reducing demands on playback processors, etc. It's what I am doing and happily so.

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One comment on “96kHz or bust”

  1. Paul writes: "Perhaps a lot to absorb here." Actually no. It is perhaps the most concise and easy-to-understand explanation yet. And the most pertinent sentence is:

    "96kHz/24 bits captures any and all info possible on a vinyl LP, tape recorder or just about any analog source..."

    It is pertinent for one chief reason: It explains reality, which is, analog signals not only have significant dynamic limitations and significant dynamic distortions as a result, but are significantly bandwidth limited IN THE REAL WORLD. Every dog I have met objected to this rule and one dog was overheard to say WOOF! A speaker manufacturer a long time ago, having had the very same experience, took notes.

    What I would add to this all is that high frequency hash, sidebands and other artifacts might exists above 96K, but they are not part of the music signal. They are distortion and you don't want these intermodulating with the signal. You don't want them in analog or digital playback. Analog would cut them off naturally, as I am not aware of any amp or preamp circuit that is active above 100K (I mean, realistically, not theoretically.) By naturally of course, stability issues come into play and feedback is used, as are filters, so "naturally" it remains.

    I'm still trying to pin down all the various explanations people describe for what they hear in analog or digital, why they might think one is better than the other. Yin and yang for some is liquid and dry for another, hard and soft for others - I think music played in different rooms can accrue any of these characteristics and descriptions. Preferences play a part, but reality cares not what I or you think.

    Most importantly, remember 96K/24bit as all you probably need. In any event DSD resolves a lot of these issues and will - maybe has already - settled the issue.

  2. A new resolution/bit rate de jour?

    But truth is, 96kHz not only sounds better when playing vinyl LPÒ€ℒs, it makes no sense to go higher. There are several reasons for this: first, 96kHz/24 bits captures any and all info possible on a vinyl LP, tape recorder or just about any analog source you might connect to the A/D.

    So what happened 44.1/16??? Is 96/24 more better exact than 44.1/16?

      1. If your recording at >350k with the new product,why bother with a low pass at all on the A/D? There's not a mic out there that will capture any thing near 175k!

        1. Because if you include frequencies higher than half the sample rate you will get aliasing errors as you are breaking the mathematical rules by which digital audio works.

          1. Of course. That's my point. No microphone can capture any sound greater than one half of the sampling frequency if its that high( if such sounds even existed)

            Your just adding parts or extra digital processing.

            1. The possibility that spurious electrical noise could ruin an otherwise perfectly good recording for want of a simple low pass filter should be taken into consideration in the design. At high frequencies this filter will not audibly degrade the recording and is easy and inexpensive to build.

  3. I hear differences, more smoothness, more air, a bit more open on the hi rez formats...a touch more dimensionality; not huge once you go beyond 96K and it is arguable if it's all worth the arguments. Hi rez is better, and then we ask, better than what? The fact is, there are many - I mean many - CDs that are far better sounding and more enjoyable (as in, music matters) than many hi rez downloads which are no better than their CD or LP counterparts. There are LPs that sound better than early CDs which, excuse my French: %*$&%! We still want the better, no matter how it is delivered to us.

    Neil Gader's editorial in the current The Abso!ute Sound P12, THE ONLY THING CONSTANT IN LIFE IS CHANGE sums it up as well and is accepting of the new realities. Gader and folks like he are not the problem in the industry - those who would maintain the status quo in a seaworld of change are. Nostalgia won't ever replace progress, not in audio, not in autos, not in video, not in the way we furnish our homes and not in running shoes. It is true that you can get good, often top notch sound with analog and the LP or tape at very high cost. It is also true that digital will, or already has, using the best rips or downloads, surpassed the capability of analog at lower cost (by far) and it is audible. That fact upsets a lot of people and I am one of the last to have admitted what I just wrote. However, I also admit to have divorced myself from much of reproduced sound for a decade while having had frequent access to live music played by the best virtuoso musicians (I mean world class) in some of the best venues. That's where I come from. And my LP collection is lying fallow - I have only so much time, and convenience also matters.

    1. "It is also true that digital will, or already has, using the best rips or downloads, surpassed the capability of analog at lower cost (by far) and it is audible. That fact upsets a lot of people and I am one of the last to have admitted what I just wrote."

      Well there's hope for you after all. Eventually you might also admit an electronic watch will keep just as accurate time or better and look a whole lot more attractive than that little box of spring, gears, and cogs you carry around on your wrist and "at lower cost (by far)" too.

      "ThatÒ€ℒs where I come from. And my LP collection is lying fallow Γ’β‚¬β€œ I have only so much time, and convenience also matters."

      That's the reason you should buy Paul's new product. It will allow you to transfer all your phonograph records perfectly to your i-pod and you can sell your watch to use the money to buy the world's best earbuds. Only don't forget to take Michael Fremer's advice and demagnetize your records before you record them. You wouldn't want any compromises to their sound quality considering how highly you prize that. John Atkinson agrees....sorta. πŸ™‚

      1. OK Soundminded, it is possible, after all, that we can communicate on the same frequency? I'd be the very first to buy Paul's LP converter if converting LPs would make sense for my lifestyle...as I said I have little time left - on this planet. Relatively speaking, the space ship isn't lifting off as of yet.

        As for the watch (I don't own and will not own that particular model or anything approaching its expense). However, you really need to recognized that there are people who eat at LaCirque several times a week and pay $49 for an appetizer (that I personally find second rate.) I was a guest, not an idiot.

        As for hahax's comments about tape, the rules still stay in place. 13 bits and that's it.

        The limits that apply to digital technology applies to analog as well - even more so. Analog tape has real FR and dynamic range limitations. It is very good, but it is not perfect sound forever. Take that back, it is not perfect sound for the next five years. It's better than any LP made from tape. It is not as good as direct to disc LP, which is dramatically better than tape.

        1. I don't normally make comments about people's spelling or grammatical errors since they're usually irrelevant, the meaning or intent is clear, and I make them myself but yours are so frequent and make your postings so confusing, I'm not sure we can communicate. For example, your first sentence here is a declarative sentence but you put a question mark at the end of it. Are you making a statement or asking a question? Reversing 2 words would turn it into a question. I'm not sure if we can communicate if you can't be more precise. I'm not a nitpicker but I think this is more than that. For example, on August 20 at 3:49 PM you wrote: " I have not met anyone who has met my match." Who is your match? Your wife? Your "significant other?" Your twin brother? No I have not met any of those and evidently from what you've said no one else has either. πŸ™‚ I know you don't like being quoted but the internet is like an elephant. It never forgets. That's why you need to be careful what you say on it. You never know when your own words can come back to bite you.

          "I was a guest, not an idiot."
          That's why I'm selling all that wine. I enjoyed it but not nearly enough to equal what I can get for it. If I were you and I was really wealthy and wanted to splurge, I'd go for the best in the cellar, a case of 1990 Beausejour Duffau Lagarosse. Parker raved about it over and over again and you can't get it. Another small production wine he raved about in the auction is Dominus. He says it tastes exactly like Petrus and it's made by the same winemaker Christian Moueix...on a property 6000 miles from Pomerol. There's 3 lots that include 90, 91 and 94, all excellent vintages. But IMO the real sleeper to go for will be the 1990 Domaine Leroy Pomard Les Vignots. Wine Spectator Magazine said they'd kill for a bottle of that. Well there's a lot of 5 in there tucked in with all those clarets and some port. If people are willing to spend $600 to $1000 or more for a bottle of wine, all I can say is enjoy it. Do you enjoy auctions? I don't. I just told them that the next time I hear from them will be when they tell me what they got for it all and how much the check will be for. I wonder if I could learn to like Two Buck Chuck πŸ™‚ Maybe if I hold my nose, close my eyes, and pretend the way audiophiles do when they listen to recordings. πŸ™‚

            1. You are correct, it has gone way out of hand. It requires professional treatment and therefore, as I have done before, I filed for divorce. I also hired an armed guard. Hopefully I will survive long enough for the papers to come back stamped.

            2. Buffalo Bob seems to have no sense of humor after all. How disappointing. Is he surrendering? Too bad if he is. In the words of John Paul Jones "I have not yet begun to fight." πŸ™‚

  4. This doesn't change the digital versus analog discussion much in a practical way. But when we say analog we normally assume LPs. But what if we were speaking of high speed reel to reel tapes. There the advantages of digital are way less. And while tape decks are hard to find now and high end tapes are too they do exist albeit in small numbers.

  5. […] PS Audio team captain Paul McGowan believes that 24bit/96kHz PCM is plenty sufficient to digitally capture all the musical information found on a vinyl LP. Essentially, 1) 24 bits are more than anyone would need to preserve the dynamic and frequency ranges of vinyl in digital aspic and 2) the use of decimation digital filters means zero group delay is only guaranteed up to 96kHz, after which it starts to creep in and higher frequencies can become more pronounced. McGowan lays it all in more detail in ’96kHz or Bust’. […]

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