Why is it advantageous to use a separate D to A converter?
The most obvious advantage is sound quality. This is really a question about separates vs. all-in-one solutions; a subject near and dear to my heart over the last 38 years. Separates are almost always superior to integrated units because the designers can focus all the hardware and software resources on executing one task perfectly. If we take the example of a receiver, integrated, or multi-use product, the internal D to A converter (DAC) in these units shares a common power supply, has rarely been optimized for high-end performance and lives in a very noisy environment not particularly conducive to high performance.
A separate and dedicated DAC, on the other hand, has all the attention of the design team lavished upon it with but one single goal in mind: performance. Properly designed, a separate DAC like the PerfectWave series from PS Audio has separate isolated power supplies, fully discrete class A analog circuitry, low noise well shielded environment and so on. Rarely are these types of features possible in a multi-task piece of kit like a receiver because there’s simply neither the physical space nor the budget to accommodate that.
What are the greatest hurdles when converting lower resolution digital audio files to the analog format?
There is a tremendous amount of sonic engineering that goes into building a quality digital to audio convertor (DAC) but frankly there’s not a lot we (or anyone) can do to make a low resolution file into a high resolution file. It’s like putting lipstick on a pig; sure it looks a little better, but it’s still a pig.
At our disposal are techniques like upsampling and apodizing filters that can help lower resolution files sound their best, but in reality, the only things you can legitimately do to help digital audio’s performance are dealing with jitter (on the digital side) and the design of the analog output stage (on the analog side).
Jitter has to do with timing of the digital audio signal and is very audible when out of whack. Jitter is inherent in both the digital audio delivery system (S/PDIF) as well as the decoding of the delivered data stream within the DAC. At PS Audio, we have invented a method of jitter reduction that we call the Digital Lens. This Digital Lens technology focuses the digital audio data down to one fine, perfect low jitter point and delivers that perfected data to the DAC for conversion to analog without any compromise; all without any digital data manipulation that most other schemes employ. So, in the PS system, we’re able to maintain bit-perfect low jitter performance without digital manipulation and the results are simply stunning.
Once we have perfected digital audio data, without jitter, we are then able to convert it to analog and here is where much of the magic in the PerfectWave system happens. All PS Audio analog stages are not based on off-the-shelf IC op amps as are many of our competitors, but rather employ fully discrete high voltage class A stages that sound as sweet as music itself. By using discrete components, such as individual transistors, FET’s, resistors and capacitors in a class A setting, PS engineering is able to build low feedback, high speed analog output stages unobtainable in an integrated circuit package. Our nearly 40 years of engineering practice comes into great advantage when analog is concerned and, let’s face it, a DAC is 50% digital and 50% analog. You can’t just throw a well regarded op amp on the output of the digital end of things and call it high-end. Sorry, that’s just marketing bullszrt.
What exactly happens inside a DAC to turn the digital files analog?
DACS are actually fairly simple devices to understand as long as we try not to discuss one bit DACS – but rather stick to multi-bit DACS such as the ones we use. In the PerfectWave series of DACS, we use 32 bit DACS with dynamic range capabilities that far exceed the threshold of human hearing. Dynamic range figures far greater than 125dB can be obtained with these DACS and this high level of performance, coupled with our state-of-the-art apodizing filters and Digital Lens technology used to lower jitter without digital manipulation results in near perfect audio that really has to be heard to be appreciated. Here’s an area where the numbers simply cannot tell the story.
But how does a DAC actually work? Well, as I mentioned it’s simple. So let’s start on the other end first: how do we go from analog to digital, then we can discuss how to undo what we’ve done to get back to analog.
Analog music that runs down a wire, say from the cartridge of a turntable, or the output of an FM radio or a microphone, is really nothing more than moving electrical energy. This electrical energy goes higher and lower in amount and frequency – in synch with whatever the music is. Think of this as battery voltage going higher and lower, quicker or slower – where the lowest is 0 volts and the highest is 12 volts (just like your car battery). If you take this moving electrical energy and connect it to a speaker or a set of headphones, the moving electrical energy makes the little speaker move back and forth – more less – quicker or slower – and this in turn moves the air and we hear sound.
Now, we want to convert this moving electrical energy into something a computer can read. Computers can only read numbers and they can do this with only 1’s and 0’s or – on and off voltage. Because they have only these two states (on/off), they are called binary (meaning two). Computers use a binary counting method that allows them to work with very large numbers – and the size of this number depends on how many bits they have. In the case of most recordings, 16 bits are used to count. In the case of the PS DAC, 32 bits are possible. So all that happens is the analog music signal goes into a digital counting device and the musical energy is converted to numbers – bigger numbers for higher levels and smaller numbers for lower levels of music.
The numbers are then stored on a hard drive or optical memory device (CD).
To get the DAC to convert these digital numbers back to analog, we use a group of switches. In our DAC there are 32 switches. Each switch turns on or off according to the number presented to it. The higher the number, the more switches get turned on. Each switch has a small voltage that turns on or off. Every switch that turns on has its voltage added to the whole – so more switches on equals higher voltage. Picture a light bulb in your home’s lamp with a 3-position switch. Each trun of the lamp’s switch and the light bulb gets brighter. In the same way, every switch that turns on adds a little more voltage to the whole and by moving these switches on and off in proper order quickly, a rising and falling voltage is generated that is the exact equivalent of the original rising and falling voltage we started with.
How is PS Audio’s approach different from other DAC manufacturers?
In the early 1990’s, while I was a partner (with Infinity founder Arnie Nudell) in Genesis, we invented a product called the Digital Lens. This was an idea of mine long ago that was actually the foundation of one of our current best selling products, the Power Plant AC regenerator line. The Lens was a digital in, digital out device whose sole purpose in life was to eliminate jitter. Not a filter or Band Aid approach to jitter reduction, which was popular at the time, but an actual digital regenerator. To work, the Digital Lens took the digital audio output from a CD player, stripped out all the clocking information and then accumulated all the digital audio bits into a very large buffer. That stored data was later reunited with a low jitter output clock at the Lens output, and presented extremely low jitter digital audio data to the user’s DAC. That same technology, upgraded to handle high resolution digital audio, has been developed and implemented in both the PerfectWave DAC’s network audio card and our PerfectWave Transport. The results are stunning. In fact, because of the built in Digital Lens, there’s no need for upsampling and data manipulation of any kind in the PerfectWave DAC, a fact we are very proud of.
While the Digital Lens is perhaps the biggest differentiator, PS Audio has other unique design elements including 100% discrete analog electronics and optional network connected. Beyond that, the presence of I2S inputs definitely set our digital audio products apart.
The HDMI inputs on the PerfectWave DAC are designed not for accepting HDMI data, but instead are utilized in a unique PS designed standard for I2S data. I2S data is the native data management system within every transport, CD player and DAC. It consists of three separate clocks and one digital audio data line. When a separate transport and D to A processor are used in a system, the I2S data inside the transport is typically mixed together to form one single data line so it can easily be transferred between the transport and the DAC through either optical, coax or balanced means. The format used to send this data is called SPDIF (Sony Phillips Digital Interface) and is found on every CD player and transport from the least expensive to the most expensive units. Once the S/PDIF signal is received by the DAC it must then be separated back into its I2S components and that is where the trouble lies. The process of encoding and then decoding the I2S data into SPDIF data compromises the audio quality on a high-end system. The PWD’s unique I2S over HDMI solves this problem in a simple elegant fashion and the audible results are openness and clarity like you’ve never experienced in your digital audio system.
Is a dedicated device required to convert audio or is the process built into other devices such as media servers and receivers?
Many manufacturers claim their products have internal DACs, but there’s physically not enough room for all the necessary processing hardware and storage to accurately convert digital files to analog. There’s a different between just converting digital files to analog and converting digital to analog while improving the quality.
What is your reaction to Apple’s announcement about releasing higher-quality digital files?
We’re extremely excited that Apple is recognizing the demand for better quality music, it would’ve been great years ago, when people started amassing their digital music collections, but it lends credibility to some of the things we’re doing at PS Audio to provide a better listening experience. When it comes to music, people are just as concerned with mobility and convenience as they are about sound quality. We recognized that early on and have strategically aligned our research and development to meet the demands of both which will be evident later on this year.
What other trends are you noticing on the music format front?
I don’t think anyone could’ve seen the huge vinyl resurgence coming. Whether it’s the warm richness of sound, better turntables or just a harkening back to more traditional times, vinyl record sales are growing almost as fast as CD sales are declining
On the other hand, the trend of streaming music sites is something we all should’ve seen coming, especially now as Spotify attempts to make its U.S debut, bringing another player to compete with Pandora, Last.Fm and Grooveshark. The sound quality of these services isn’t great, but the cost (or lack thereof) and ability to open people’s ears to new artists are a positive for the music and audio industry.
As mentioned earlier, better quality downloads are also becoming available, something I think we’ll see more of from other services, especially since Apple has given its stamp of approval.
What can we expect from manufacturers in reaction to these trends?
PS Audio has some cool things in store, but we’re already seeing more music servers and convergence type products that bring PC and AV entertainment content together. I think that progression will definitely continue right alongside a trend towards vinyl and better speakers.
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Paul McGowan
An insatiable tinkerer with no college degree, Paul McGowan began his relationship with audio when he was drafted in 1969 and served as a DJ for the Armed Forces Network (AFN) in Germany until 1973. That same year, Paul founded Infinitizer – a company that marketed the world’s first polyphonic music synthesizer, a product he invented and designed. The company only manufactured one unit and never actually delivered because the manufacturer unscrupulously stole the startup money instead of actually building products. During this time period McGowan also worked as a DJ and program director at KSEE, KZON and KXFM, in Santa Maria, California.
Undeterred by the loss of Inifinitizer, Mr. McGowan designed a phono preamplifier for the radio station. A local Audiophile, Stan Warren, heard and liked the preamp so much that he offered to buy half of a non-existent company for $500 with a goal of building and selling preamps to Audiophiles. McGowan agreed and PS Audio (Paul and Stan Audio) was born. Paul and Stan built hundreds of phono stages by hand in a makeshift garage before hiring real employees to do the same thing. Stan learned how to design and between the two, they cranked out a number of firsts in the high-end audio business including:
The first high-end integrated amplifier, the Elite, in 1975
The first high-end outboard DAC
The first high-end CD player, the CD-1 (a modified Magnavox unit with an aftermarket PS Audio designed analog stage)
The first AC power regenerator
The first external add-on outboard power supplies for preamplifiers and phono stages
Mr. Warren left the company in 1983 to form Superphon and in 1990, McGowan sold PS Audio and joined Infinity founder Arnie Nudell in forming Genesis Technologies, a world class high-end loudspeaker company. Genesis was sold to a Singapore investor in 1997. Later in 1997, McGowan reacquired PS Audio and has served as the company’s CEO ever since, guiding development of the PerfectWave line of products and other technology breakthroughs.
Paul McGowan was born in 1948 in Hawaii before moving to Orange County California where he stayed until 1969. He is married to his lovely wife Terri and has four sons, all successful entrepreneurs like their father. Paul’s hobbies include skiing, hiking, kick boxing, artisan bread baking and photography.