Tag Archives: digital audio

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

I smell a new DAC coming from PS Audio!

Keeping time

We’re all aware that jitter in the digital audio stream is to be avoided.

Jitter is all about timing deviations where the audio data isn’t exactly where it is supposed to be in time. You can think of it like someone being early or late for their scheduled arrival time.

For jitter to be audible it has to be unpredictably late or early. (If we know the data is always late or early by the same measure then it’s easy to compensate).

The reference for our digital audio data is called a clock. With every clock cycle, the digital audio system looks to see if there is any incoming data that arrived on time. If there is, life’s good. If that data is slightly late or early, we get a “jerky” output of digits fed into our DACs.

To make certain this doesn’t happen we often add queues (buffers) where we collect all the on time, late, and early data together before passing them on to their final destination.

This digital queue describes perfectly PS Audio’s Digital Lens technology.

Here’s the thing. Data stored on a hard drive, streaming over the internet, or your home network don’t have too much of a schedule to worry about. Think of them as travelers told to show up at a certain time and place where they are then expected to join a queue before being assigned to a time schedule.

In other words, stored and streamed data don’t have clocks that are important to their final arrival time. Thus, they cannot have jitter to worry about.

Only when we enter the world of master clocks as dictated by (for example) CD/SACD transports do we need to worry about jitter. (In these cases the transport supplies the master clock to the DAC)

Data entering a DAC must at some point fall in line to be properly queued up and marched in time so as to avoid jitter.

Where that happens is all important.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Missing information

I am always fascinated to watch those slow-speed nature videos where you watch flowers open and plants grow. Or, the opposite. A high-speed camera that slows down the wing motions of a hummingbird so we might see what in real life we cannot.

Those cameras (both film and video) are essentially digital: frame by frame they capture a single moment in time. When played back they look continuous.

Each form of slow and fast digital capture offers a glimpse into that which our analog senses cannot perceive. In other words, we get more information than what we are able to consume in our analog world.

The same is true today in digital audio. Whether high-sample rate PCM or DSD, modern A/D D/A converters can capture and playback far more details and frequency extremes than we can perceive.

All of which to point out that somewhere along the technology timeline we moved from being able to seamlessly capture nearly all the information in a live performance (the end of the analog era) to today capturing more than our human auditory systems can use.

Now that it is no longer a question about missing data, the challenge becomes converting that data back into the analog world.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Another piece of the puzzle

I often tackle the same question multiple times. With each new answer to the same question, the different angle of attack seems to illuminate the lightbulb of understanding for at least one person.

An aha! moment. For me, that’s reason enough to keep trying.

We’re all perhaps a bit weary of me beating the DSD horse. I get it. But, I am also convinced that most of my readers don’t quite understand the difference between the two main digital audio formats: PCM and PDM. And I think it’s important to shine a light on it.

One of our HiFi Family members, Tony Plachy is a retired physicist with a gift for explaining hard-to-follow concepts.

Here’s from one of his comments:

“There is something very special about DSD256. I will try to explain what it does and how it does it. First, lets call DSD256 what it is. PDM ( Pulse Density Modulation ) which is a special case of PWM ( Pulse Width Modulation). I have been to seminars and lectures where notable mastering and recording engineers have said that the remarkable thing about PDM is that when the sampling rate is high enough ( and DSD256 is certainly high enough ) and you make a digital copy of analog music and the convert the copy back to analog what you get back sounds like the original. To say it another way is DSD256 makes exact copies.

I have a DSD recorder that i use to make copies of my best vinyl. It copies at DSD128 and the plays it back at DSD64. During the recording I can toggle between the copy and the original listening to the headphone feed from the recorder. To these old ears the mastering and recording engineers are correct.

How can this be? What does this happen with PDM and why does PCM ( Pulse Code Modulation ) seem to leave a digital footprint on the results? The answer is two things, one of witch I have all ready mentioned. First, the sampling rate must be high enough ( DSD256 or at least DSD128 ). Second, with PDM the amplitude of the analog signal is NOT ( yes, is NOT ) digitized. You can see this for yourself if you go online and find an article that shows the DSD output of digitizing a sine wave. Even if you are not an EE ( Electrical Engineer ) it should be obvious that all you need to do is use an analog low pass filter to get the sine wave back. Do not ever try this if you have the PCM output from digitizing a wave, all you will hear is horrible noise.

So does PDM do this for all music? The answer is yes, it does. To understand this you need to go online again and first look up a guy named Fourier and then look up how a square wave is made from a Fourier series. If you understand this it will be obvious that PDM can make exact copies of all music.

End of lecture, do your homework, this will be on the final exam! 😉

Thanks, Tony!

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Great one from Paul.

Engine timing!! I set the timing on my car too, but like Paul, 40 years ago. Now, other than doing routine maintenance on our cars, I’d have no idea how to fix anything under their hoods.

Crossing the chasm

My father’s father, Claude, would probably find our modern technological wonders magic. Or unbelievable.

Imagine getting in a time machine and over coffee explaining to him that we can talk with anyone anywhere in the world. That within a matter of hours we can be transported in luxury anywhere in the world. That the entire knowledge base of humanity is available at the touch of a button. And let’s not forget our ability to watch any movie or listen to any music by just asking a robot.

He would likely just smile and think me a nutjob.

But, here’s the thing. I could probably manage to help him understand many of the basics including a turntable-based stereo  system. It’s not that far-fetched to show the principles behind the technology. A string and two cans would be a great help.

Now imagine explaining how digital audio works. Try to make sense of an optical disc and a pulsating laser to a person who just saw their first automobile.

Between the electro-mechanical era where inventors like Edison and Tesla could convert physical objects like horns, wires, wax, and needles into miracles, and the age of digital electronics spans a chasm so deep and wide as to be either magic or witchcraft.

In fact, do you think you could explain to someone with zero knowledge of electronics or science how music is stored and retrieved from an optical disc or a solid-state memory?

I would wager to say that when we crossed the deep divide between the electro-mechanical age and were thrust headfirst into manipulating electrons that we lost our grip on the ability to manipulate our own world. It wasn’t that many years ago I could set the timing on my car. Now my car has no timing to set.

It feels a bit humbling to have crossed the greatest chasm of humankind.

I am happy to be here. What a ride!

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl

Putting the crutches away

If you’ve ever had the misfortune of requiring crutches you’ll know they can be addictive. Once you rely upon a crutch it’s a bit of an ordeal to put them away and trust again your freestanding abilities.

I remember the first time I read about musician Mark Knopfler’s first foray into digital audio. So “digital” sounding was Brothers in Arms that he ran and reran the output of the recording studio DAC through analog processors until the digititis was expunged.

That was a pretty big crutch.

Today, recording engineers have settled into the use of crutches never contemplated back in the days of analog recording. Practices like ultra-warm microphones, digital sweeteners, warming compressors, and spot EQ (to remove harshness), are used as a standard operating procedure to make up for digital’s “sound”.

Which means, of course, that an entire generation or two of recording engineers and musicians have gotten used to the idea that this is just the way you do it. They don’t know why or the history of how this developed.

It’s just the way you do it.

One of the challenges we at Octave Records face is the unwinding of all these built-in biases. With the rare technology of 4X DSD as our recording medium, we don’t have limitations imposed upon us. The recording process is finally free of a “sound”.

It’s not analog. It’s certainly not digital.

Now we can focus on choosing microphones, preamps, cables, and monitors based solely on their sonic merits.

We can now put the crutches away and learn how to walk again.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl

I have stories, but in the world of high end audio, there are lots of them and probably more interesting than mine.

Magnetic symmetry

There was a time before digital audio came onto the field where we had magnetic symmetry.

Our sources—both vinyl and tape—were magnetically coupled, while our playback too was driven by the power of magnetic motors in our speakers.

Magnets in and magnets out.

No physical connections between ins and outs.

All coupled through magnetism.

Today, of course, we’ve managed to eliminate the magnetic isolation (many would call distortion) of our sources.

All that is left is our magnetically coupled motors that move the air so we can hear sound (and even electrostats eliminated that).

On the source side, one could have argued that bits are magnetically stored first on floppy discs and later on hard drives but, alas, it’s almost all solid-state now.

I am pretty certain none of this actually matters. Not at the level of technical excellence most of us have arrived at.

I did find the idea of how everything we listened to was magnetically coupled intriguing (if not totally nerdy).

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Paul’s confused.

One way street

If you freeze bread and then toast it, the results are marvelous. Crunchy on the outside and soft and pliable on the inside. Try reversing the process and the results are more than disappointing.

I wish I understood more about one-way streets. Why some things work best in one direction but not in another.

Make a side-by-side recording using a digital recorder and a vinyl LP cutting lathe.  It doesn’t take a pair of golden ears to hear the digital audio capture sounds nothing like the vinyl.

Yet, we can make near-perfect digital captures of vinyl records.

I have long suspected that this one-way effect is due to digital audio’s greater resolution and dynamic range capabilities than those of vinyl. It’s easy enough to put a pint of water into a gallon bucket, but the opposite doesn’t work.

What’s troubling to me is that as we move Octave Record releases into the realm of vinyl, we find that the one-way street argument falls a bit short. Direct vinyl masters from the DSD masters seem to sound more dynamic and musical than the original DSD files.

This has me scratching my head.

The sound of vinyl may remain an unsolved mystery that in my lifetime never gets resolved.

It’s a one way street to confusion.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Grails, holy and hopeful

One of the more famous literary motifs is the idea of the Holy Grail, a metaphorical vessel with miraculous powers providing happiness, eternal youth or sustenance in infinite abundance.

Grails, both holy and hopeful, can apply to any number of aspirational audio goals. For me, that grail is to be found in digital audio.

We’ve long known that digits are digits and thus can be endlessly replicated without loss. That said, we’ve also known that digital delivery and processing are prone to differences that are most audible.

The Grail would, for me, be to design a series of digital audio devices that are agnostic to the storage, transmission, and processing of bits. That no matter how one gets those bits delivered and processed, the audible results would be the same.

We are a long way away from drinking from that grail vessel, though with PS Audio’s recent innovations of galvanically isolating inputs and CPUs from the digital outputs we’re more than one step closer.

Grails, both holy and hopeful are what keep most of us in research and development going.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl


Swedish electronic engineer Harry Nyquist figured something interesting out. If you want to capture sound using digital audio conversion, you need to sample at twice the frequency you hope to preserve.

Thus, if your goal is to capture without loss frequencies as high as 20kHz, you need to build a stereo system that gathers twice that frequency—40kHz. Add to that requirement the fact such a system gets wigged out if you feed it frequencies higher than the maximum sample rate, one is required to make sure a steep filter is applied before conversion from analog to digital.

Which is how we wound up with CD’s sampling rate of 44.1kHz. We need the 40kHz part to keep Harry Nyquist happy, and the extra 4kHz bit to keep engineers tasked with building a brick wall filter from jumping out of windows.

But here’s the thing. If Nyquist was correct (and he was) that we can capture with perfection half the frequency of our sample rate, why do we need higher sample rates?

After all, we can’t hear anything above 20kHz (and most of us can’t hear that high).

The answer lies not with Mr. Nyquist, but instead with the challenge of steep low pass filters. As my friend Robb Hendrickson puts it: “Whether you’re recording at 44.1 or 48kHz, you are LITERALLY applying a low-pass filter to NATURE!!!”

Indeed, it’s not the lack of 20kHz (because there is no lack of it), but the effects of filtering we hear.

If we need to apply a low pass filter to nature, it had best be really, really, high. Like 100kHz to 200kHz.

Harry gave us only half an answer. The other half is figured out by our ears.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

This is technical, but I can tell you that if you pay proper attention to galvanic isolation in D/A digital to analog circuits, you will have less noise, better resolution and a better sounding stereo.

PS Audio is seemingly just discoverint this, but my T+A DAC 8 DSD is galvanically isolated and sounds incredible!!

Galvanic isolation

As we talk more of the virtues of galvanic isolation in digital audio, perhaps it’s of value to take a moment out of our busy day to understand just what that means.

The term galvanic refers to a galvanic cell, named after its inventor, Luigi Galvani. The Galvanic Cell is technically described with a mumbo jumbo of words: “an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell.”

More simply stated, it’s a battery.

This can be confusing because when we refer to galvanic isolation we’re not talking of batteries, but rather we’re referring to electrical isolation. A battery operated flashlight can be said to be electrically isolated, but so too could we suggest a battery operated DAC is electrically isolated, yet we’d be incorrect unless that DAC’s inputs and outputs are connected via optical cables.

And it is to this last point that we get to the heart of the matter.

To be galvanically isolated there can be neither physical connection nor direct electrical current involved. Even our old friend ground must not touch. In this way, whatever happens on one side theoretically shouldn’t be mirrored on the other side of the circuit.

The methods of achieving such isolation are to connect via non-physical means such as magnetic fields or light—hence the use of isolation transformers and optocouplers.

None of this is easy to digest, but at least we can try and gain a little understanding.