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You are reading the older HTML site Positive Feedback ISSUE 41january/february 2009
Ten Questions about Computer Audio with Gordon Rankin of Wavelength Audio
Computer Audio has become the new rage in audio and for good reason: one has an easy and instant access to all their music as well the ability to search out countless other titles via the internet. The issue is simply where to start, though the answer is quite obvious: get a computer, rip and store the files, and then play them back to some DAC. Of course being audiophiles …err the nuts we are… the questions start to pile up rather quickly. Mac or PC, and then once you got that settled, there is all the minutiae related to just setting-up that computer’s OS and configuration. Then comes how best to rip and how best to save the files, and then to where? Okay, so now that I have my files, how best to play them back and how best to get the files out of the computer and to what DAC? Yadda, yadda, yadda… each question leads to further questions to clarify the previous that then lead to other questions that suggests another question and …a downward spiral down into the rabbit hole we go. So I went to the 2009 CES and found not only a wealth of information, but a wealth of confusion or at the very least, a wealth of disagreement among those that are either in the recording/software side, the hardware-side, and/or the "expert" sides of computer audio. Now CES is not the best place to get all the answers… time is an issue as is finding all the people to ask, so I came up with 10 ‘key" questions (these are my 10, you may have others or perhaps might not find these of any benefit to you, but I chose them because they are of interest to me and besides they reflect the most common or important areas that seem to pop-up whenever one talks about computer-based audio, so go pound silicon if they don’t work for you.) and emailed them to 12 people in the industry to answer. Their responses are here...
1. Let’s start with interfaces; the obvious choices are USB, Firewire, Optical, and S/PDIF. What is your opinion on any of these interfaces? What if any, are the advantages or disadvantages of one over the others in terms of resolution, jitter, etc.? If we are talking about serial interfaces for audio then there is basically only four: 1) S/PDIF which would include optical (never used anymore), BNC/RCA (single-ended, BNC best), Toslink and AES/EBU. 2) USB which comes in Sync (no one uses this for DACs only ADCs), Adaptive (most people use) and Async ISO 3) Firewire which only comes in Adaptive suffers the same fate as Adaptive USB. 4) Driver specific protocols most of which are Firewire and USB oriented. I guess board level also but given the fact that there is not a computer out there with a decent enough power supply for any High End card then let's leave it at USB and Firewire. The least of the diminishing returns is Async USB as it does not require custom drivers and has the best jitter. That being said the same results (jitter wise) can be had with Driver (meaning it requires a device driver to work) specific interfaces. Adaptive USB has jitter that is much more than well done S/PDIF as follows in a recent test I did with the Wavecrest Jitter Analyzer that I have @ 44.1kHz from the output of the receiver (i.e. USB or S/PDIF receiver). TAS1020 USB Adaptive Mode 2838ps TI/BB PCM2706/7 I2S output 3433ps S/PDIF streamed from Prism dScope III analyzer (really low output jitter!) 629ps S/PDIF streamed output from Mac Book Toslink 1607ps S/PDIF streamed output from Apple Airport express Toslink 2418ps Streamlength Async USB Cosecant Numerator module TAS1020 78.2ps S/PDIF is a gamut of problems and as such it really depends on so many variables that I would not even want to start on that. Most computer S/PDIF ports are Toslink and most that I have measured are pretty high in jitter. Of course jitter can be reduced by upsamplers and reclockers. BUT all of these methods are like low pass filters. The more jitter there is the less it remove. 2. With regards to software there are also strong opinions as to some being vastly superior (or for that matter, inferior) to others; people clearly hear differences in how files are being played back and therefore prefer one over the others. There is also a growing opinion that Pro software is the only way to go and that using iTunes, WMP, MAX, or other free software playback programs (FooBar, JRiver, MAX, etc.) is not the way to go. That is, these are sonically and musically inferior to the Pro software because the Pro software (say for example Amarra, Izotpe, etc.) is simply "better" at playing back music files. What is your opinion on what is going on here? That is, why would any of these programs be superior—or for that matter, inferior—to another with respect to say a .wav file in any resolution: 16/44.1, 24/96, or 24/192? Is it a matter of timing and jitter? Issues with the operating software and processing? The fact that some software runs "cleaner" than others—that there is nothing running in the background to muck things up? Or as some suggest that the "math" is simply better in some software than in others? I would say that the PRO/HE Software would be better. The main reason is that more time can be spent on the outgoing stream. Whereas commercial software simply was written for a wider audience and therefore lacks some of the things we would want as high end playback. I know of several PRO companies who are writing real full featured programs because they see a niche in today’s High End Audio marketplace. Remember jitter is a function of an audio clock wrapped around audio data. In the computer there is no jitter. There is no jitter in any of the serial interfaces above except S/PDIF. There is intrinsic jitter in all audio receivers including USB, Firewire and even S/PDIF. 3. Let´s move on to ripping. As with the above, there are proponents that claim only certain software, and optical drives for that matter, can "accurately" rip a CD. That they can clearly hear differences between rips via different means; even though the rips are bit for bit perfect. Any thoughts on what is going on here? Is there an advantage to using specific ripping software or drives over another? Say iTunes, WMP, Max or whatever when compared to say EAC? Five years ago EAC was it. Now everyone can do this. It's been documented in several PRO magazines. 4. File formats. Any reason why a .wav, AIFF, or FLAC file is better than say Apple Lossless? Again people suggest a strong preference for one over the others, so something must be going on here? Files that are compressed like FLAC and Apple Lossless never sound as good as .wav or AIFF. But it's best to use AIFF as the Meta data is stored in the file and therefore if you lose the hard drive the backup files will be easy to recover. If you have .wav files and loose the drive... good luck you might as well start over. We have seen the compressed file syndrome on slower computers. The faster they are the harder it is to tell the difference between say an AIFF and Apple Lossless. 5. There is also a movement towards Pro DACs. Naturally there are DACs of varying quality and performance, but is there any reason why a PRO DAC would be better than a DAC made by a manufacturer from the audio community? Say ones of comparable quality and build? Different Climate... PRO developers do huge volume and therefore don't get as crazy as designers in High End. When I talk to PRO designers about High End audio they think we are all nuts. Ask Ashley about different USB cables and why they can't sound different. In HE Audio everything makes a difference. 6. Along those same lines, what makes one DAC a better choice for computer-based audio than another? Jitter reduction, chip sets, power supply, etc? YES as above, everything makes a difference. 7. What do you see as being the most important factor in getting the best sound in computer-based audio? That is what should the consumer address with the greatest concern when setting up a computer-based audio system? Everything should be considered important, why should I look at the clocks or jitter any differently than looking at the output or the power supply. Everything is of the highest concern. 8. Along with that, what do you see as being the most important factor in NOT getting the best sound in computer-based audio? That is, what can have the greatest potential to adversely affect the sound in computer-based audio? User's who don't read the simple instructions and rip their entire library with Error Correction off. 9. Some suggest that they computer must be audio dedicated. That is it must be "built" or configured for the specific purpose of only playing music and that any and all non-audio related programs and such must be eliminated. Your feelings on this? Is it important or not, and why so? In PC land yes, in Apple land no. 10. Where do you see the greatest impact to come in computer-based audio for the future? USB Class 2.0 were we can do 24/192 and above natively without drivers. This is available now on MAC OSX 10.5.x but not in Windows or Linux yet. Also new front end software... The greatest thing about computer audio (other than the fact that you listen to more music) is that you get updates and upgrades in software which allow you to reach a higher state without ditching the entire investment. Gordon Rankin is the designer and founder of Wavelength Audio. Gordon heard his first real high end system comprised of mainly tube based Marantz gear, AR-1 speakers and a Thorens table as a college freshman. After six years of working through several majors, he ended up with a BSEE along with 4 minors (one being music). Audio seemed like the natural choice and in 1981 Wavelength Audio was born. During the early years his time was also shared by work in the Computer Industry (Hardware and Software development for the Computer Communications sector of PC, MAC, UNIX and Mainframes) until the Cardinal 300B SET amplifier got a review in 1994 (Component of the Year) and broke things wide open. Gordon primarily designs and builds USB DACS, SET Amplifiers and for fun, Tube Based Guitar and Bass Amplifiers. Use the links below to read other responses to these questions Larry Moore and Eric Hider of Ultra Fi Audio Designs Andreas Koch of Playback Designs Steve Nugent of Empirical Audio Gordon Rankin of Wavelength Audio Jon Reichbach of Sonic Studio/Amarra Vinnie Rossi of Red Wine Audio John Stronczer of Bel Canto Designs Daniel Weiss of Weiss Digital Audio Vincent Sanders and John Hughes of VRS Audio Solutions Charles Hansen of Ayre Acoustics Pete Davey of Positive Feedback Online
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