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

Nyquist

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.

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 morning, I learned that my favorite Hi-Fi writer ever, from Stereophile Magazine, Art Dudley, passed away on April 14th of this year.

I had no clue Art was sick and this came as a shock to me, as well as just plain sad. He wasn’t that old, in his early to mid 60’s,  and always looked healthy and robust in the pictures and videos of him, I was able to see. Truly, life is fragile and this has hit home for me.

Art loved Single Ended Triode amps and tube preamplifiers, which I’ve owned many of in the past and one of his favorite pair of loudspeakers is an old high efficiency Altec design from 1966, called the Flamenco, similar to one of the speakers I own and use now. I say “similar to”, because the driver I use, the Altec 604, has been brought back to life by Great Plains Audio, so while mine is a copy and my cabinet is a one of a kind thing I designed and had someone build, the driver does use original Altec tooling, so an Altec driver. Art would probably disagree and I wish I could have had that conversation with him.

He used old vintage Garrard and Thorens turntables that he re-conditioned himself and digital audio was pretty much an afterthought for him. I don’t think he thought digital was listenable enough for him to enjoy. He also didn’t sweat room acoustics and audio tweaks. Probably better off that way. He was also an accomplished guitar player.

I was hoping to go to the 2020 Axpona show, where he would have been and meet and talk to him for a couple of minutes. Maybe have a discussion about that Altec driver. I’m truly sorry I won’t ever be able to now.

Anyway,  Art was an opinionated writer, but could put sound into words, like no other writer I’ve ever read.  I can tell from things he wrote about and things I read about him that he was a good husband, father, animal owner and human being. I just watched a video of him from 2017 describing his system in great detail, his thoughts on stereo equipment and at the end, he is driving somewhere and sees a turtle in the road. He pulled his car over, took out his floor mat and pushed the turtle to the other side of the road. Only a good person would do this and I will miss him.

Our thoughts go out to his wife and daughter and all his friends and co-workers  that were able to interact with him often. I regret never meeting him in person, although I felt I knew much about him from his writings. He will be missed by many.

 

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.

Becoming a statistic

We’re all a statistic somewhere: a number, one of many that someone, somewhere, keeps track of. Maybe you’re one of X thousand digital audio subscribers, or perhaps you’re among the few that only purchase vinyl, but somewhere you’re showing up as a statistic.

Most of us wish to belong to a group, family, or collection of like minded people. There’s strength in numbers and our decisions to move in one direction or another are validated by the others.

What’s interesting to me is the conflict between how I feel inside vs. my needs to be part of a group. Inside, I am an individual—a separate entity unto myself. No one knows what’s inside my head nor how I am thinking. I believe I am unique in the universe. Yet, on more than a few levels, I qualify as a measurable statistic. A predictable entity. Regardless of the clutter of seemingly unique motivations in my head, someone, somewhere can pretty accurately guess what my next moves are going to be.

Even if I decide I don’t want to identify as part of a group I remain a predictable statistic: I am part of a group that doesn’t want to be part of a group.

I know. All this keeping track of people seems kind of creepy, right?

If belonging to a family or group of likeminded people—our tribe—is what makes us stronger and more resourceful than what we alone can achieve, then what’s creepy about keeping track of the members? It’s how we know there is more than just one in the tribe.

I for one am fine with being counted amongst my fellow audiophiles and music lovers, even if it means someone else can predict what the future might look like.

 

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.

Even guys like Paul can be audio flakes. How many times do we get gobsmacked by something in our audio system, like a tweak, to forgetting about it the next day, or figure out that it’s even not as good as before? Has happened to us all, plus he has a phono stage to sell and I don’t begrudge him for that.

The problem with exuberance

As I waxed enthusiastically about my vinyl LP experience shared in yesterday’s post, it never occurred to me I might have been divisive. That readers not included in the event might feel slighted or worried I was now suggesting a major shift in my long held views on DSD and digital audio, that vinyl’s superior to digital (I am not).

And that’s the problem with exuberance. The energy and excitement of the moment are at the exclusion of the bigger picture.

I suppose there will always be a downside to emotional reporting, which is likely why people like the Chairman of the Federal Reserve Board speak in such muted tones using carefully groomed words. One hint of excitement or disappointment in any one direction could send financial markets soaring or plunging.

Ours is an emotion-packed field. We work hard at coaxing out buried nuance and exposing our souls to the joys of home reproduction in the hopes of eliciting excitement—even exuberance.

Putting a damper on the excitement meter is not in the cards for me.

Now, where’s that grain of salt?

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.

In search of miracles

I am constantly on the hunt for miracles. I don’t want just improvements or brighter polish when it comes to my audio system. No, in fact, it’s miracles I am after though they do seem rather far and few between.

The most recent miracle to cross my path is the new Stellar Phono preamp. After nearly 30 years of focusing on digital audio, this miracle piece of gear has transformed the way I think of vinyl. Now, I have to reevaluate every decision I have made over the past three decades.

The beauty of this particular miracle is that it is additive to the main music system. Instead of transforming the way I think of digital audio, it has added an entirely new dimension of music’s enjoyment that I had long ago abandoned as dead.

Now, that’s a miracle.

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.

Setting levels

Where we set our audio system-level can make a tremendous amount of difference.

One of the problems I often see in digital audio is people hell-bent on setting the volume level in the app they are streaming from. In almost every case, this is exactly the wrong thing to do. Changing the playback level at the source is a really bad way to reproduce high-performance audio. For example, if you’re using Audirvana, iTunes, or Bit Perfect, the last place you want to adjust the playback level is in those programs. The moment you do that any chance of bit-perfect performance flies right out the window.

The exceptions to this are when you’re using a program like Roon, or our upcoming program Octave. There, the levels can be adjusted right in the music management program because the source remains bit perfect. What you’re actually doing, in that case, is controlling the DAC itself through the interface. Thus, it looks like it’s happening right in the app when actually you’re doing it just right.

It’s a common mistake to make and one we see all the time. Your preamp or DAC is where you should be adjusting the level.

Keeping digital audio at its bit-perfect best is always going to sound best.

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.

Biting bits

Yesterday we talked of the difficulty understanding how digital audio bits could be higher or lower quality. Would we hear differences in sound quality between digital bits streamed over the internet vs. those found on our local hard drives or CD players?

The simple answer is no. Given identical source files, bits are bits when transferred between data sources and their end clients. There are no clocks associated with streamed, stored, or transferred data. So, for example, one cannot accurately suggest that the “timing is off” on CD or hard drive stored data since the data itself are unrelated to timing devices. Once that data gets delivered to our DAC the server or CD player has added a clock to the bits. That is a horse of a different color. If the timing of streamed bits is off, it’s the server or CD player we can point a finger at.

The quality of the switch handling our network data is meaningless. It either faithfully passes the bits or it does not.

So, why do people hear differences with various switch types and connecting cables managing our internet traffic? My guess is other reasons than data corruption. Fact is, we know the data is uncorrupted so finger-pointing probably needs to change direction: shielding, power supply noise entering the DAC, ground noise or contamination.

When investigating a commonly held belief it’s always beneficial to assume the many observations are correct. That attitude leads one to quickly dismiss the obvious and dig deep for underlying possibilities.

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.

Filling a vacuum

When we think up new products sometimes it’s because we have a novel idea like the Digital Lens. That’s a product/technology that solved a problem most people didn’t even know they had.

Then there are the obvious ones like stereo amps and audio preamps to fill out a system.

But sometimes products come into being to fill a vacuum. And surprising that’s why we’re committed to building a new category of loudspeaker.

To fill a vacuum.

When our customers ask for loudspeaker recommendations to match their musical tastes we’re at a loss of where to send them, which is weird because there are more speaker manufacturers than any other category in our industry. You’d imagine with all that choice there’d be a slam dunk for people who want true full range, high resolution, easy setup, adjustable depth, extended dynamic range, musically breathtaking, visually appealing, small footprint, affordable loudspeakers.

But there’s nothing we know of that fits that bill (though admittedly that’s quite a laundry list of requirements).

So, as we’ve done in the past with AC power and digital audio—and even as far back as our early standalone phono stage—we need to step up to the plate and do it ourselves.

To some, this post will sound like over the top marketing fluff or just plain boastful. Probably is. But to those who have genuinely sought out the aforementioned laundry list in earnest and found themselves settling on the next best choice, this is all too real and a problem worth solving by someone.

Anyone.

I wish we could do it sooner.

 

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.

Air gaps

The long-awaited PS Audio music server, Octave, is inching closer to making its debut in late 2019. Since I’ve not written much about it recently, I thought you’d enjoy an update about one of its innovations, a new invention called the Air Gap Audio Interface or AGAI.

The AGAI solves a big problem in digital audio servers, contamination by noise and electrical detritus.

Inside a server, you have a noisy computer. As it chugs away at its tasks it jitters and pollutes the output signal feeding the DAC. This is why, we believe, FLAC sounds differently than WAV even though the bits are identical. A FLAC file (for example) requires far more bit crunching to extract the original bits than does a WAV file. Those crunched bits contaminate the final output signal through mutually shared power, ground and physical signal traces.

How can we fix that?

Imagine that the noisy computer inside the server was not in the server box and was instead far away (as we are doing in the upcoming Ted Smith Signature DAC). Its noise and ground contamination would not be a problem as long as we took its distant output and regenerated it in a Digital Lens.

Since our goal is to build a one-box server, the next best thing is to physically isolate the two systems within a single chassis. To do that we need separate power supplies, ground planes, physical boards, and at the end of the proverbial day, a physically isolated connection between the internal computer and the output Digital Lens. That’s where the AGAI comes into play. By bridging the gap between the internal noisy computer and Digital Lens by nothing more than light traveling through air, we get excellent isolation.

(In the upcoming TSS DAC the problem is solved with two chassis: a digital and analog separated too by light using a fiber optic cable between the two.)

We’re all familiar with digital data transmitted through lightwaves using a TOSLINK cable but that won’t work for either of our applications because of TOSLINK’s bandwidth limitations. But that isn’t a show stopper. It just means we have to step up our use of technology. Some of the highest speed data in the world travel on beams of light.

Whichever method is used, AGAI or high-speed fiber, transmission of digital data over lightwaves offers the possibility of getting noise and jitter out of the signal and gets us that much closer to musical perfection.