Dr. AIX, aka Mark Waldrep Ph.D., has launched a companion website called RealHD-Audio.com. You can visit the site and read his daily blog posts (even sign up for daily delivery to your email), explore the topic of HD-Audio and get free samples of 96 kHz/24-bit music. The new site talks about all HD formats including DSD 64/128, HD PCM and DXD.

The site contains lots of useful information and if there's anything you want me to discuss, please feel free to let me know.

You can leave comments on the site and review the post archives to read about production techniques, music, equipment and people in the business.

There has been a resurgence of interest in vinyl LPs during the past several years. Many audiophiles assert that vinyl LPs sound “warmer” or “more analog” than digital recordings...especially standard resolution compact discs. Even makers of high end digital audio equipment such as digital to analog converters and disc transports make the claim that vinyl is the reference to which all else is measured.

I was dismayed to read the “Back Page” interview in the most recent issue of The Absolute Sound. Neil Gader asked 10 questions of Paul McGowan, the CEO of PS Audio. Near the end of the interview Neil asked if vinyl was still the reference for audio fidelity. To which Paul answered, “Absolutely, I think digital struggles to come up to the standards that are easily attained by vinyl.” His opinion is widespread among audiophiles.

I do not agree with Paul or any of the other advocates of this position. If we were only talking about the sound of early CDs in comparison to LPs, then I might waffle on the point. It’s true that early compact discs were made from equalized tapes that were intended for vinyl and the emphasis and dynamic modifications made to the audio were ill-conceived and produced poor results. But in this age of high definition audio recording and playback, it is absolutely untrue that vinyl provides the reference against which all audio reproduction should be compared!

It is true that vinyl has a particular sound associated with it just as film looks different than video. Audiophiles have come to appreciate the sound of vinyl. The distortions of this very highly developed reproduction method have come to be known as “warmth” and “depth”. But they are distortions to the actual sound received by the microphones. I have no argument with the sound of vinyl among the various flavors that are currently available to music fans. Where I draw the line is when someone elevates vinyl to the reference standard. If by “reference standard” we mean sound reproduction that meets or exceeds the capabilities of our human auditory system. Vinyl doesn’t even come close...but HD Audio has the potential to.

Let’s first take a look at what I call the “provenance” of a particular recording. By that I mean, the specific production steps that a track goes through prior to arriving at your speakers. Music starts with musicians/singers performing in front of microphones and recording equipment (it’s true that a lot of electronic music is captured directly to the recorder without mikes but that’s a story we’ll address later). The original recording pretty much establishes the fidelity of the recording. These days there are some very sophisticated tools that can remove clicks, pops and hiss from older analog recordings. There even some state-of-the-art tools that can selectively remove the frequencies of say a cell phone from a piece of recorded music...but they are expensive and require a very skilled operator. That’s why I say the fidelity is “pretty much” established at the time the musicians played the tune.

In the past, ensembles would assemble in a studio or in a performance space and play. The audio engineers would strategically place as many microphones as they deemed necessary (minimalists prefer fewer mikes and others like the sound of many) around the space. The feeds were mixed together in a mixing console and the output (either mono or stereo) recorded by a disc cutter or on an analog tape machine. The resultant recording is referred to as the master. And if you wanted to hear that recording at its absolute best, you had to be present during a playback of the master in the control room. Otherwise, the next stage in the production process degraded the sound by about 6 dB (which is a lot). Analog tape copies lose 6 dB of dynamic range and signal to noise ratio when they are copied. There is even a term for this degradation. It’s called generation loss. The “safety” copy is used during the mastering and disc cutting process on the way to the vinyl master. Record labels and engineers simply can’t risk damaging the original master.

In the world of audio fidelity things like dynamic range and signal to noise ratio are measure in decibels, a logarithmic measuring system. Human hearing is the most sensitive of our 5 senses. Our ability to hear extremely quiet sounds AND tolerate very loud sounds is astounding (the amount of energy received by your ears from the quietest to the loudest is billions of times greater). Using decibels, humans experience pain and can suffer severe hearing loss if exposed to 145 dB. A full symphony orchestra cranking out the final variation in Mussorgsky’s Pictures at an Exhibition - The Great Gates of Kiev might hit 125-135 dB for brief moments (many woodwind players where ear protection if they sit front of the brass section). Standing in the front row of a Metallica concert produces sound levels that exceed 135 -140 dB for prolonged stretches.

So how good are the various recording technologies at capturing the dynamic range of the real world? Analog tape, the recording technology most often used in the production chain of a vinyl release, tops out at about 72 dB. If you use a noise reduction system such as Dolby SR (Spectral Recording) you can push that number up to 90 dB, but risk distortions to the harmonic accuracy of the recording. So the vinyl records that audiophiles claim as a reference are very limited in dynamic fidelity...never more than around 60-75 dB of signal to noise ratio can be delivered by an LP. Still they can sound pretty great...in spite of the limited dynamic capability.

HD Audio according to my definition is audio that is recorded and reproduced (both ends of the production chain must be included) with specifications that meet or exceed those of our human hearing sense. With regards to dynamic range, a PCM (Pulse Code Modulation) encoded audio track using 24-bit linear digital words has the potential to reach 144 dB of signal to noise ratio. In reality, the equipment we use falls somewhat short of this theoretical upper limit. Current state-of-the-art converters and recording machines spec out around 125-130 dB...still a whole lot higher than the best analog machines and vinyl reproduction. Each PCM digital bit equates to about 6 dB of signal to noise ratio according to the theory.

So a vinyl record (made from the safety copy) has a dynamic range of 60 -75 dB, which can be fully encoded with only 12-13 bits (less even than the 16-bits available on a standard definition compact disc). While an HD Audio project that is carefully done can accommodate 120-135 dB of signal to noise ratio within its 24-bits. From the dynamics side of the fidelity question, vinyl isn’t even in the ballpark.

We’ll talk about frequency response, linearity, timbral accuracy and timings issues in the next installment. But the next time you read that vinyl is “still the reference”, you’ll know better. Take the initiative to listen to a great HD Audio track...something with a lot of dynamic range...and you’ll know why I’m so passionate about this. The timbale on the Ernest Ranglin recording we did is a prime example. On vinyl it would have to be compressed to fit...on the HD Audio file or DVD, all of the dynamic range is delivered. It just sounds more real and contributes to the musicality of the track in a way that has previously been impossible.

A few months ago, I received a phone call from Dr. John Q. Walker, the Chairman and founder of Zenph Sound Innovations, based in Raleigh, North Carolina, a company that has developed important, new music technologies and a line of award-winning recordings of classic performances. I had heard of the work that Zenph was doing in the area of "re-performances" of famous pianists and their recordings. I had even heard the Gould recordings and was thrilled at the sonic quality and interpretations of his 1955 Goldberg Variations. Zenph Sound Innovations has received rave reviews of their Glenn Gould and Art Tatum releases on Sony Masterworks and I was well aware of their work.

It was a welcome surprise to find that John was aware of my audiophile label AIX Records and iTrax.com. He wanted to know if I would be interested in releasing the latest project from Zenph, the re-performance of "Rachmaninoff plays Rachmaninoff" in any format other than standard definition compact disc. Sony Masterworks has limited their release to the CD version, which had received rave reviews from Stereophile and The Absolute Sound, but were not going to issue a high definition disc. They had agreed to let Zenph partner with iTrax.com for the HD Surround tracks. Very good news for those of us that are addicted to high definition sound and surround mixes.

Of course, I was thrilled at the chance to partner with Sony Masterworks and Zenph, and become the home of this important recording…in HD Surround!

So what exactly is a re-performance? This is the explanation provided on the Zenph website:

"Author Kevin Bazzana refers to our process as a “live realization of the original interpretation.” Zenph(R) Studios takes audio recordings and turns them back into live performances, precisely replicating what was originally recorded. Our software-based process extracts every musical nuance of a recorded performance, and stores the data in a high-resolution digital file. These re-performance files contain the details of how every note in the composition was played, including pedal actions, volume, and articulations – all with millisecond timings.

 

These re-performance files can then be played back on real acoustic pianos fitted with sophisticated computers and hardware, letting the listener “sit in the room” as if he or she were there when the original recording was made. Most importantly, the re-performance can be recorded afresh, using the latest microphones and recording techniques, to modernize monophonic or poor-quality recordings of beloved performances.

 

Important to this process is the use of high-resolution data. Those familiar with the MIDI specification (now more than 25 years old) may know that regular MIDI isn’t really sufficient for capturing and replicating fine nuance. It’s like the difference between regular TV and high-definition TV. The high-resolution specs we’re using vary among instruments, but all offer 10 bits of data to preserve the velocity of each key (compared to 7 bits in regular MIDI), as well as detailed information about the key and pedal positioning.

 

We feel the word “re-performance” summarizes this technique perfectly."

 

The ability to convert older recordings with limited fidelity into high-resolution re-performance data, and then to newly record them with state-of-the-art audio equipment AND to deliver them in full HD surround to music consumers is a transformative event in the history of recordings.

 

I've been fortunate to be able to compare the Rachmaninoff tracks played from the standard-resolution CD and from the HD surround files here in my studio. While the sonic quality of the CD is absolutely first class and up to the full capabilities of that format, the clarity and sense of spaciousness offered by HD surround offers a completely different perspective.

 

The addition of Zenph Sound Innovations' "Rachmaninoff Plays Rachmaninoff" to iTrax.com is a huge step forward for those seeking REAL HD recordings and for the future of our site. I'm extremely happy to be able to feature this album in our iTrax.com catalog and I look forward to adding new items as they become available. Thanks John for believing in iTrax.com!