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Positive Feedback ISSUE41
Ten Questions about Computer Audio with Jon Reichbach of Sonic Studio/Amarra
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.?
FireWire is a high performance interface and one of its advantages for audio is that it supports a streaming mode, called isochronous mode transfers, that allows a guaranteed bandwidth. USB does not allow this and there can be dropouts as a result.
In addition, USB and Firewire do not inherently carry a clock and do not influence jitter (if they do then jitter can be effected). On the other hand they emit large amounts of RF radiation requiring care in shielding the analog converter.
Toslink can provide a clock but one its 'problems' is the high amount of jitter. The nice thing is that the jitter is masked as white noise, and in fact can sound quite good as most converters can handle this well (the PLLs have an easier job).
Sonic hardware is decoupled from the clock and there is no jitter introduced from the FireWire; we feel this is better.
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?
The simple answer is that it’s the math. The long answer is that just as a hardware designer pays attention to all aspects of a design it is the same with software based audio processing core. You really do need to know when to round, when to truncate, when to use 32 bit vs. 64, when a multiple vs. a bit shift, etc. You need to get it all right. We have learned that even some very subtle changes can make a dramatic effect on the sound.
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?
If the resulting files are bit for bit identical then there is no difference. The key might be that, are they ripped identically? For example is error correcting on or off, and is it properly identified when they occur? That said there are advantages to using your own software to handle the error correction, and perhaps most important to be able to read the "whole" audio disc—audio gaps and all. This allows one to reconstruct the CD with the original timing between songs.
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?
Lossless is lossless as far as we can tell. The only change I can imagine is that the CPU has to work a bit to convert the lossless and there may be some buffer memory access patterns that generate more RF (than straight PCM). I was told that Apple lossless is not lossless for 24 bit data—it compresses to 16 bits. This would not be a good thing.
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?
The main reason would be that Pro devices can be better at clock recovery as well as handling RF as they are in noisy environments. The other difference is what the designer is looking for. I have noticed that Pro converters are more "transparent" than other DACs which impart a sound. For a Mastering Engineer it is important that the converters do not color the sound in anyway.
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, all of the above. Most designers are using similar chips so it comes down to good design.
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?
First off, for all computer audio it is the playback software and its audio processing engine (as discussed above). Followed closely by a good DAC with an excellent clock, internal or external; which we find is critical for great sound. This is followed by good speakers that are properly set up.
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?
Bad software and bad shielding of RF noise in equipment. Bad speakers and a bad room do not help either.
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?
Well you can certainly build computers that are quiet, no fans, discs, etc and these are a special build. Having dedicated computers is also not a bad idea as you never know when some application will decide to index your drive (like Spotlight does). For our professional customers we recommend a dedicated machine or one of minimal use, so I would not expect an audiophile to be any different; especially if using an older machine. A newer machine is more than capable.
10. Where do you see the greatest impact to come in computer-based audio for the future?
If we look say 20 years or more a nano will hold all the music ever made. The problem will be managing the content not the format. This content will be all web based as physical media will be gone. Everything will be done through a computer.
Jonathan Reichbach, President, has over 25 years experience in the audio and software engineering fields. A veteran of 6 startups, he was Director of Software Engineering at Sonic Solutions, and was one of the principal software developers responsible for Sonic Studios' earlier audio products. He holds a MSEE from University of California at Santa Barbara and a BSCS from the University of New York at Stonybrook.
His first software program was a Bach two-part invention, written using Music-4 on a PDP-11 computer in 1976. Things have progressed since then.
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