More about the PonoPlayer Design
Many of the more technically inclined have asked for more details about what is so special about the PonoPlayer design. Charlie Hansen, founder of Ayre Acoustics, and one of the major contributors to the technical audio circuit design of the PonoPlayer that will ship in October, provided the information in this memo to share with you.
But first, let’s be clear that we have no publishable measured “specifications” for the PonoPlayer as of our Kickstarter campaign. While we have a basic design that is a working prototype, and it sounds great today, we have been evolving the design of the Player throughout the last year, and will continue to make changes through the next month or so, as we approach our handoff to manufacturing for October shipments.
When we have stabilized the design of the Player and built a sufficient number of test units, we will begin to measure the audio specifications of the Player, and will have those “specs” available at shipment.
One of the primary reasons we chose a crowdfunding platform was to raise the necessary funds to completely finish the design of the PonoPlayer. So, obviously, we cannot publish “specs” on an unfinished product. We belive our backers understand this idea. Now, on to the design of the Player.
For the best audio experience, we begin by getting the highest resolution audio recording available from the labels. Our goal is to deliver to the consumer the file that is the closest possible representation of what the artist heard in the studio when the album was being made.
Our singular aim during the development of the PonoPlayer was to build a device with one purpose: the playback of music at the highest possible level of performance given the boundaries of the design. This design called for a small, portable structure capable of storing high-resolution digital files and converting them to analog music, thereby providing a more-than-fulfilling experience for the listener. This product wouldn’t function as a phone, WiFi router, Bluetooth transceiver, portable gaming platform or GPS widget. Any additional features would only detract from the resolution of music in its fullest dimension, and thus, the enjoyment we know possible when music is reproduced with this level of fidelity.
The music is downloaded and stored in a format called FLAC (Free Lossless Audio Codec), a widely accepted, robust, industry standard. It allows for the compression and subsequent storage of large audio files without the loss of critical data. All information stored on the original file can be retrieved with zero loss once the FLAC algorithm decompresses the file. This provides the best of both worlds: compact storage and high potential fidelity. Founded by Charles (Charlie) Hansen (chief engineer and product designer), Ayre has been designing and building high-performance, award-winning home audio electronics for more than 20 years. With their feet firmly planted in both the digital and analog domains, we felt they were the perfect choice for a partner that could design an audio circuit capable of championing the difficult and delicate challenges of high-resolution audio playback.
Everything Ayre has ever made has had fully balanced, all-discrete, zero-feedback analog circuitry. Even Ayre’s digital products employ custom digital filters. The reasoning behind the use and implementation of every one of these technologies is to fortify the presence of the signal and defeat noise in the path of that same signal. Without this, the rendering of high-resolution music would be a futile task, as the listener wouldn’t be able to hear the actual benefits of high-resolution audio.
In the PonoPlayer, Ayre began their work by designing the circuitry after the main processor retrieves the audio data from the memory and presents it in "3-wire" form - audio data, bit clock, and word clock. They chose the just-released version of ESS's top-of-the-line ES9018. It has two channels, comes in a very small package (5 mm square), and is extremely customizable, able to tackle the rigors of sensitive, low-level signal path design.
The filter generally favored by Ayre is a minimum-phase digital filter (to eliminate pre-ringing), with a "slow" roll-off, to minimize the overall amount of ringing (ringing can be thought of as an oscillation in the digital signal, causing all sorts of errors if misconstrued as actual signal to be converted to analog, which is engineer-speak for music). For the Pono Player’s D/A (digital-to-analog) converter Charlie went a step further and used a moving average filter for both the double and quad sampling rates because it has no pre-ringing, no post-ringing, no overshoot, and no undershoot (these create inaccuracies in the rendering of digital signal and sacrifice fidelity). In other words, it has none of the digital artifacts (digital artifacts also add to distortion and occlude signal) at all.
The DAC chip’s output comes in the form of current, so Ayre designed a proprietary, fully discrete, fully- balanced, zero-feedback current-to-voltage stage. This then goes to a fully discrete, zero-feedback buffer stage to drive both the headphone output and the line stage output. The output impedance is roughly 5 ohms, allowing the PonoPlayer to drive any headphone on the market with minimal frequency response errors.