Positive Feedback ISSUE 41
january/february 2009

Ten Questions about Computer Audio with Vinnie Rossi of Red Wine 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.?

It is very clear to me that computer-based audio (i.e., using a computer as the transport for music playback) via the USB port has the potential to sound better than even the best CD transports that output S/PDIF. I have proven this with my own DAC design and many others have as well. Compared to S/PDIF (coax or optical), DACs using the USB can offer significantly lower jitter vs. S/PDIF if implemented properly. For example, our DAC has a USB input that converts the USB data directly to I²S (the native data format fed to the actual d/a converter chip), which eliminates the jitter generated in recovering the clock signal from the S/PDIF data stream.

Besides the potential for lower jitter via USB, there are advantages of ripping music onto a hard disk using software that offers error correction. Unlike with CD transports, playback via computer audio does not read the data off a CD on the fly from a laser and optical pick-up. The data is read off a hard disk, buffered and streamed out on the USB port without timing information—this is added later in the USB DAC and can be done so very precisely.

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 s 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?

Yes, a lot of it has to do with how the software processes the data from the music files on the hard disc. I have not tried all the different programs for playback, so I cannot comment on how they all compare. No matter which one you use, it is very important to deactivate features such as EQ, sound level normalization, digital volume controls, etc. as these do interfere with the original data.

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 believe that ripping in iTunes (with the error correction feature set to ON) does a fine job and extracting the bits off of the CD, and is very easy to use. The important thing is that all the bits from the CD are transferred to the hard drive without errors.

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?

I have not found Apple Lossless to be inferior to AIFF or the original .wav. Upon playback of the lossless file, all the data of the original .wav is recovered, bit for bit. This is the definition of "lossless." There is no loss of data compared to the original. The file is only compressed upon storage to the hard disc, and fully recovered upon playback.

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 terms of sound quality, there is no reason why a DAC designed for Pro-audio would necessarily be better than one designed for high-end home audio. There will always be very good and not-so-good sounding DACs in both pro audio and home audio.

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?

There are many areas that are important to pay close attention to when designing a great sounding DAC (for computer-based audio or conventional CD transports). In no particular order, here are some to consider:

• The actual DAC chip – they do NOT all sound the same. Each has its own sound. However, you can have two DAC units using the same DAC chip but still sound very different. This is because there are many other factors, such as:

• The power supply for both the digital and analog sections. They should both be as clean as possible and isolated from each other. The analog output stage. There are many choices, such as using opamps vs. discrete transistors, feedback vs. no feedback, tubes vs. solid stage, passive I/V conversion vs. active, single-ended vs. balanced, etc. It all sounds different.

• The digital receiver chips – no matter if it is a USB receiver, S/PDIF receiver or some other one. The chip, how it is configured, how it is powered, etc. all makes a difference.

• The circuit board layout – how all the parts are laid-out on the board, how the traces are ran… it all affects the sound.

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?

I believe the DAC plays a large role in the overall sound of a computer-based audio system. The consumer needs to choose the DAC that sounds best for them and in their system. Sometimes, you need to put aside specifications and graphs and just listen to the DAC in your system and see if it is recreating the music in a way that connects with you and keeps you excited and involved with the music. It doesn't matter how well something measures or how good it is in theory if it ends up sounding sterile, analytical, or boring.

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?

It is easy to adversely affect the sound in computer-based audio if you are ripping your music using lossy compression (e.g. mp3), or if you are using any of the EQ, sound enhancer, digital volume control, etc. settings in your playback software. These features molest the data that is fed out to your DAC.

In terms of DAC design for computer audio (using USB), powering the USB receiver chip of a USB DAC from the computer's USB bus (the +5V from the USB port) has the potential to adversely affect the sound. The USB port's power comes from the noisy, switch-mode power supply of the computer. In our Isabellina DAC design, the USB receiver (as well as the rest of the DAC) is fed from linear-regulated SLA battery power.

If the DAC has a USB input, but converts the USB data to S/PDIF (which then needs to be fed to a S/PDIF receiver chip and then converted to I²S), this does NOT take advantage of what USB has to offer and the results tend to not be any better (and can even be inferior) to using a good CD transport that outputs S/PDIF to an external DAC.

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?

I see no reason why you cannot use the same computer as your audio server and also run non-audio related programs on it. If your computer has non-audio related programs on it, it is not a problem if they are not running. Even if they are running (e.g. surfing the web while playing music), it shouldn't be a problem as long as your computer has enough resources (e.g. CPU, RAM, etc.) to handle both. As I type this on my MacBook, I am listening to my music (iTunes) via my USB DAC and it sounds fantastic and there are no issues with drop-outs or anything like that. Perhaps this could be an issue if you are using an older computer.

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

Computer-based high-end audio is growing each and every day. More and more audiophiles are getting involved with it and finding it hard to go back to conventional CD players because they love the convenience and special features—it is a lot of fun and very addictive! I believe the playback software will become more interactive—allowing the listener to learn more about the artist, access their music collection in new ways, and hopefully this will also help get their friends and family more involved and learning about our hobby and how high-end home audio transforms our listening experience and makes us connect with the music on a whole new level!

In terms of the hardware, so many companies are releasing DACs that have USB inputs because they realize that computer audio is the future of digital audio playback and it is here to stay for a long time. You also see more companies coming out with music servers, Wi-Fi streaming devices, and interactive remote controls to put our music collections at our fingertips. These are very exciting times to be in this industry and it is growing stronger every year! 

Vinnie Rossi  is the chief designer and founder of Red Wine Audio.

http://www.redwineaudio.com

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