Miscellaneous

Editor: Way back in 1979, when I was a staff producer for Columbia Records, I was asked to produce Jerry Goldsmith's seminal music score for Star Trek: The Motion Picture.

I started looking around for something futuristic that would be compatible with the movie's ethos, and while I was at the Audio Engineering Society (AES) convention in downtown Los Angeles, at the Biltmore Hotel, I happened to stumble on a small exhibit in a Sony demo room. They were showing a PCM-1600 digital recording system that processed sound at 16-bit/44.1kHz, as well as a hand-wired prototype digital editor. Don Ellis, the VP of A&R at Columbia Records, okayed the purchase of a PCM-1600 and two Sony ¾" BVU-200 video recorders to record the live stereo mix for the album, alongside Ampex 16- and 2-track analog tape recorders.

On playback on the scoring stage, I immediately noticed that the PCM-1600, with its limitations of 16 bits and only 44.1kHz sampling, did a reasonably good job of reproducing what it had recorded—that is, without any perceived loss of high frequencies or analog print-through. When it came time to edit and master the score for the album, Sony graciously loaned me their hand-built prototype digital editor, and Star Trek: The Motion Picture became the first digitally recorded and edited soundtrack album of a motion-picture music score, four years before the advent of the CD.

Fast-forward 34 years. To celebrate [the film's 35th] anniversary, it was decided to go back to the original 30ips, 16-track analog masters, archive them at 24/192, and do new mixes in high resolution. The resulting mixes brought forth all the excellent room tone and natural reverberation of the 20th Century Fox Scoring Stage that the 16/44.1 recording lacked. It was a revelation.

Around the same time, I attended a reunion concert of the Buffalo Springfield at the Santa Barbara Bowl. I had originally recorded their second album, Buffalo Springfield Again, which was when I first made music with Neil Young and Stephen Stills. After the concert, Neil asked me to come backstage, as he had something that he wanted me to hear.

Neil had this dream, that someday there would be a system that reproduced the music exactly as we heard it in the studio before it became a CD with 22% of our soundfield or, worse, the lovely 3% of MP3, and that was the beginning of Pono.

When it came time to bring Pono to reality, Neil asked me to join him, and I jumped at the opportunity to help bring the sound that we work so very hard to get in the studio into the average Joe's or Jane's home, car, or earphones. I've made extensive listening tests in my studio, comparing the output of an analog 30ips stereo master against the output of the Pono Player and I have to say that it is stunning. The analog circuitry that Charles Hansen and his crew at Ayre Acoustics devised sounds beautiful, with the ability to capture and reproduce the sound accurately, especially in the balanced mode. After a long 35 years, we've finally got a proper audio playback instrument that truly is representative of the music.

One last question to those who say that you don't need more than 16/44.1 or can't hear above 20kHz: Why would any of the artists, producers, and recording engineers be happy with less than they've heard in the studio? High-resolution audio is here to bring back the emotion and joy of listening to music. That's what Pono is all about.—Bruce Botnick, Pono Music

Editor: Thank you very much for the insightful review of the PonoPlayer. I truly believe that you have captured its essence. Specifically, it is the easiest entry into the world of high-performance audio of which I am aware. The entire goal of high-performance audio is to tear down the walls between the original music performance and the listener.

The barriers of entry to high-performance audio are normally twofold:

1) Price: A high-performance audio system will range in price from several thousand to several hundreds of thousands of dollars. The PonoPlayer delivers the musical satisfaction of systems costing hundred of times more.

2) Knowledge, skill, and experience: On the Ayre website, we recommend that people purchase Jim Smith's book, Get Better Sound. The reason is that, in my experience, equipment is at most responsible for only half of the final sound quality of a music-playback system. The other half requires knowledge, skill, and experience in myriad areas—room acoustics, vibration control, EMF fields, RFI, mechanical properties of materials—and, perhaps above all, a commitment of time and a passion for experimentation.

In contrast, with a portable player, simply put it in your pocket, put on your headphones, and you're all set. The only tweaking even possible is to replace the stock headphone cables with aftermarket upgrades. And as John Atkinson will no doubt write about in a Follow-Up, the PonoPlayer has a unique balanced mode that raises its performance to an entirely new level. Number one in a field of one.

One point touched on in JA's "Measurements" section highlights the limitations of working with a portable audio player. Specifically, all of the Pono's power comes from a single rechargeable 3.7V lithium-ion battery. This leads to two different difficulties during the design phase:

1) With nonportable equipment, current draw is rarely a consideration. Sometimes, a large power amplifier must have attention paid to its heatsinking, to ensure reliability as well as nonhazardous temperatures on exposed surfaces.

With portable equipment, every single milliamp of current drain shortens the battery life. This puts extremely tight constraints on what can be achieved while still maintaining an acceptable playing time between charges.

2) The de facto standard output level for portable audio players is 1V RMS. Not only is this 6dB lower than specified for home equipment, it is 10–16dB below what is often found in real-world products. Boosting the output level is an easy way to achieve improved signal/noise measurements, and living in the real world of 1V output makes it impossible to match the specifications of stationary equipment.

As JA found, at some point the numbers become meaningless. The ambient noise of our listening situation makes the noise floor of the PonoPlayer a moot point. It still delivers the musical goods: the ability to feel the intent of the performer.

Also, I would like to delve into the topic of output impedance. I would kindly ask Stereophile's readers to please ignore any "rules of thumb" or other "conventional wisdom" that says that a certain number assigned to the output impedance is "good" or "bad." Instead, simply let your ears be your guide. The following explains why.

Remember that the audio circuitry of the PonoPlayer is a completely zero-feedback design. Without the artifice of feedback to force the output impedance to a fixed point, it is worth noting the formula for the output impedance of an emitter follower. Very simply, it is equal to 26 divided by the bias current (expressed in milliamps).

The output stage in the PonoPlayer is a Diamond buffer, essentially taken straight out of Ayre's KX-R Twenty preamplifier. This circuit in the PonoPlayer idles at about 4mA and runs in class A-A/B. As there are two complementary output devices per phase, at low levels (class A) the output impedance is roughly 26 ÷ 4mA ÷ 2 emitter followers = 3.25 ohms.

At higher playback levels, the output stage leaves class-A and enters class-A/B. Then, only one of the transistors is on during part of the audio cycle, so the factor of 2 goes away. But here is the beauty of an open-loop design: the more current that is drawn (eg, from a low-impedance load), the more current passes through the emitter follower, which in turn reduces its output impedance.

The bottom line is that a set of high-impedance cans will be driven by a relatively low output impedance in the range of 3 ohms or so, which is far more than adequate. And if the user connects lower-impedance headphones and/or drives them at higher and higher levels, the output impedance drops further. It becomes a self-correcting situation so that the PonoPlayer can drive even the lowest-impedance loads without difficulty.

What's more, connecting to the PonoPlayer with balanced cables will connect two separate amplifiers to each transducer, each driven 180° out of phase with the other. This will double the available voltage swing, thus quadrupling the output power (as well as canceling all of the even harmonics and rejecting imperfections in the power supply).

The end result is that the PonoPlayer is the only portable player to date that will drive virtually any headphone to satisfying levels, regardless of impedance or sensitivity, without the need for an external headphone amplifier, especially when used in balanced mode.

Again, thank you for the efforts expended both in the review as well as in the comprehensive measurement suite that Stereophile has developed (and continues to) over many decades of fine audio reporting.—Charles Hansen, Ayre Acoustics