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POSITIVE FEEDBACK ONLINE - ISSUE 41
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Ten Questions about Computer Audio with Daniel Weiss of Weiss Digital 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.?

In terms of resolution, all can go up to 24 bits (which is plenty for audio), some can potentially go even higher.

In terms of jitter, well jitter matters in the DAC, i.e. where the conversion of digital to analog takes place. If the local clock in the DAC can be the master clock for the player, life is simple. E.g. with a Firewire link that can be easily achieved—the computer can be slaved to the master clock in the DAC. On the other hand, if the DAC is slaved to the player, a well designed jitter suppression circuitry has to be employed, independent of the interfacing format used. I properly designed jitter suppression circuit can take huge amounts of jitter down to very low jitter frequencies and feed the DAC a nice, clean clock.

I don't have a particular preference in terms of interface formats.

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 player application is capable of playing back the files as "bit transparent", i.e. no bits are changed between file and DAC, then it does not matter which player is used. With some care regarding drivers, DSP plug-ins, volume controls, and sampling rate settings, a bit transparent playback can be achieved with most players. There is unfortunately, still some know-how involved. But that will change as players for highend Hi-Fi purposes emerge. If a bit transparent player seems to sound different to another bit transparent player, then it is time to check that with a blind test and/or check the DAC for jitter sensitivity. I.e. if a DAC is sensitive to jitter and/or EMI (Electro Magnetic Interference) from the computer, then it may well be that different players sound different. But if that is the case then any other applications running concurrently on the computer can make a difference. Moving target.

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?

Using e.g. EAC (Exact Audio Copy) or iTunes with a specific ripping setting is a good idea in any case. It makes sure the CD is ripped as well as possible. But once the data is on the hard disc in the computer and it is a bit for bit perfect copy, then claiming that one can hear whether that bit for bit perfect copy has been made via one or another hardware/software is insane.

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?

All formats mentioned are capable of playing back the exact original music, bit for bit identical. So no difference. Again, if the DAC used reacts to the computer activity (via jitter or EMI) then there is  potentially a difference between decoders. That is not a fault of the format, but rather of the DAC.

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?

No reason that one should be better than the other per se. This movement is because of the price point. Pro DACs usually are cheaper.

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?

Basically the source should not matter at all for the DAC. The DAC gets data plus timing information from the player. The data it conveys to the DAC chip; the timing information it uses to generate a highly stable "jitter free" sampling clock. Whether the player is a computer, CD transport, or whatever does not matter for a properly designed DAC.

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?

Number one is the DAC. See above. Number two is the proper set-up of the player software, such that the signal is not altered in the player or by the operating system. Unwanted signal processing, sampling rate conversion, etc. should be avoided.

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?

A mediocre DAC, a player which changes the data, and lossy compressed music files.

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?

Not important. Today's computers are fast enough to handle 192/24 playback and at the same time do some spreadsheets, etc.. The DAC must be insensitive to jitter and EMI as mentioned above, or else all that computer activity can be detrimental to the sonics.

10. Where do you see the greatest impact to come in computer-based audio for the future?

Computer based playback opens the possibility to play back high resolution files. It has yet to be seen whether Blue Ray or DVD-R with .wav files will take off as media for hi-rez audio, but downloads will be a successful business. More and more "high-end" labels are offering hi-rez downloads.


After studying electrical engineering Daniel Weiss joined the Willi Studer (Studer - Revox) company in Switzerland. At Studer he worked in the digital audio lab for five years. His work included the design of a sampling frequency converter and the digital signal processing electronics for digital audio recorders.

In 1985 Mr. Weiss founded the company Weiss Engineering. From the very beginning the company concentrated on the design and manufacture of digital audio equipment for mastering studios. The modular "102 Series" system was the first product. Even today this system is still up to date (24/96) and is still sold. Hundreds of Mastering Studios around the world use it every day.

http://www.weiss.ch


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

Tony Lauck

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

Kent Poon of Design w Sound

Charles Hansen of Ayre Acoustics

Pete Davey of Positive Feedback Online

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