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You are reading the older HTML site Positive Feedback ISSUE 41january/february 2009
Ten Questions about Computer Audio with John Stronczer of Bel Canto Designs
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.? USB, Firewire, AES/EBU or S/PDIF from a PCI card, Ethernet, Toslink or wireless. All are viable up to 24-bit/96kHz with USB 2.0, with Firewire, AES/EBU and Ethernet viable at up to 24/192 or higher. Jitter is the biggest problem for achieving quality digital audio playback. Each format has advantages and disadvantages—in the best case a professional AES/EBU setup using a PCI card plus a word clock input slaved to the DAC. The downside is the obvious complexity and expense. In any case robust jitter filtration must be designed into the DAC so that jitter can be rejected upstream—otherwise you chase your tail because you are never being sure that you're hearing everything that the original file can give. 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? If the playback software doesn't allow bit-perfect playback then all bets are off. Assuming most of the software mentioned does pass bit-perfect information—my testing shows this to be the case unless changing volume or EQ—then what's left is jitter. And that has to be dealt with at the DAC to achieve the potential performance that digital audio promises. In fact there's a new S/PDIF receiver technology that looks quite promising… 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? I've had good luck using iTunes in Correction mode on a Mac. The optical drive should be good quality and set up correctly, although some PCs seem to use inferior-quality drives that lead to excessive rip-times. Whatever the software it has to be bit-perfect. 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? Assuming you're dealing with a bit-perfect recording then like I say, all that's left is jitter! Unless you knock it down EVERYTHING upstream of the DAC clock is suspect. 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? In actual fact no, except that Pro DACs meet their specs and are of relatively uniform high quality. But as we all know sound quality depends on more than just specs. Pro DACs may deal with jitter more effectively—slaved word clocks, etc.—and to mimic that performance you need a desktop PC and Lynx PCI card, but that seems rather clumsy. For general home audio a superior jitter-rejection scheme is needed to those found in DACs today. 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? All of the above plus, I'd say, the type of digital/analog filters, the IV stage, and the quality of the passive and active devices in the analog output stage. 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? In a word... JITTER! 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? Some of the worst sound I've heard was Toslink from a Mac or Airport Express. Of course, we've had excellent results with our USB Link 24/96 with its high jitter rejection! Perhaps the best sound to be had is using a Lynx AES/EBU PCI card. Another tip is never allowing your software to do sample rate conversion—it's a real problem with iTunes as it only plays back at a single rate unless you select the native rate in the Midi application. Now that's a real pain when you have high resolution and Redbook CD data on the computer. Someone needs to come up with a killer app that ensures iTunes plays back the native sample rate of the file. 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 the PC world it's probably best to use a dedicated machine as there are so many glitches with XP—it's rather crude. At Bel Canto we use an iMac for all sorts of things and it still functions very well as an audio source. But I still get the best sound from our CD-2 into the DAC3, though the margin is getting smaller with our new USB Link 24/96. Still 24-bit/88.2kHz and 24/96 files on the iMac will slay me! 10. Where do you see the greatest impact to come in computer-based audio for the future? When we hammer the jitter out and download and play all sorts of high resolution audio at 24/88.2 and up we'll really start enjoying its potential. This is gonna be sweet and I can hear it coming! Just remember that it's still early days for computer playback and we're all breaking new ground. John Stronczer is the Founder, CEO and designer of Bel Canto Design, LLC, a state-of-the-art manufacturer of award-winning analog and digital source components and amplifiers for home and professional applications since 2000. From 1998 to 2002 John was a Principle Engineer at the AMCC Minneapolis Design Center (MDC). MDC developed ultra-high-speed (2.5, 10 and 40 gigabits per second) SiGe and CMOS integrated circuits for fiber optic internet infrastructure communications. In addition to founding the design center, John was the lead designer for a 40Gbit/s parallel fiber transmitter and AMCC’s family of 10Gbit/s serial transimpedance amplifiers for OC-192 SONET systems. Before that he co-founded and was a managing partner of Ten Mountains Design LLP in Minneapolis, MN, a mixed-signal integrated circuit consulting firm. Ten Mountains developed CMOS, Bipolar, BiCMOS and GaAs integrated circuits for communications, sensor instrumentation, memory and medical applications. Ten Mountains developed one of the first BiCMOS RF cable modem ICs jointly with ADC Telecommunications. Ten Mountains also developed one of the first fully-integrated RF CMOS transceivers for low data rate communications jointly with Honeywell. Ten Mountains was also a pioneer in analog integrated circuits for high-speed short wavelength VCSEL-based fiber optic communications. In 1998, Ten Mountains was acquired by San Diego-based, Applied Microcircuits Corporation (AMCC). John began his career as a Research Scientist at Honeywell Physical Sciences Center in Bloomington, Minnesota in 1986. At Honeywell he specialized in GaAs integrated circuit development for communications systems in support of defense and aerospace product development. Projects included a next generation high data rate secure communications chip set for the government, ultra-low-noise analog sensor electronics for IR sensor applications and the world’s first complementary GaAs operational amplifier for radiation hardened environments. John Stronczer has a Bachelor of Science in Electrical Engineering from the University of Minnesota Institute of Technology and has been awarded seven U.S. patents in integrated circuit design. 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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