As more audiophiles dip their toes into computer-based audio they discover, to their dismay, that it's far more complicated than conventional audio. In fact, the level of complexity involved in even a basic computer audio system dwarfs that of the most baroque multi-amp, multi-crossover, multi-driver traditional audio installation. Why? In computer audio the hardware, software, and cables interact with one another to affect the sound. Two very similar setups can sound different merely because particular details of their configurations are different. Unfortunately even small variables can have substantial sonic implications. Going from a 3' USB connection to a 6' one is audible in some systems. While this may be a tweaker's paradise, it's a reviewer's and manufacturer's nightmare.
In conventional audio it's relatively easy to substitute one component for another in a reference system and get an accurate impression of that component's intrinsic performance. In computer audio the complicated interrelationships between different parts of a system make a clear assignment of sonic characteristics far more difficult. Generalizing that a particular interface is better or worse than another can't be ascertained by merely doing A/B tests in a handful of systems. There are simply too many variables at work to be able to make these kind of broad statements about universal performance.
In an effort to try to clarify what does and does not make a sonic difference in a computer-based audio system, let's look at some of the basic building blocks of computer audio. The goal here is to give you a better idea of what's important and what to look out for when you assemble or make changes to your own computer-based audio system.
I'm not going to delve into the whole PC versus Mac issue here. Both systems have unique advantages and disadvantages. But whichever you use, both suffer from similar inherent problems related to properly matching software with hardware to attain optimal performance. My goal here is to educate you about the parts and pieces, not to recommend universal solutions.
CPUs and RAM
You might assume that getting the fastest, most powerful computer processor available is always the best way to go for a computer music system, but this is not the case. If you have a dedicated music computer whose sole function is reproducing music you can use a less powerful processor without experiencing any sonic degradation. Many computer-music experts recommend or use the lowly Mac Mini as the center of their state-of-the-art computer music systems, while others use fairly basic no-name PCs.
What is far more important than processor speed or power is whether your processor can and will support the latest generation of software. For anyone putting together a Mac system, it's better to have an Intel-based Mac that can use the latest Snow Leopard operating system than a more powerful, earlier-generation computer with a Motorola processor. The newest $599 Mac Mini trumps any G5 desktop for music-system use. On the PC side, having a unit that will run the new Windows 7 operating system should be a real advantage since this new version of Windows promises a more streamlined audio-processing chain than the ones currently available on Vista or XP systems.
A universal fact, regardless of operating system or processor, is that more RAM is always better. Although I'm not fond of generalizing, I'll go on record as recommending that you should always install as much RAM as you can afford and as your processor will allow. Maximizing RAM minimizes disc-caching (when a computer writes and then reads data from the disc in lieu of keeping it in RAM). And why is writing and then retrieving data from a disc so bad? Because each time data is copied by being written to a disc and then read off that disc it increases the likelihood of data errors and timing errors that degrade sound quality. Disc-caching also slows down a computer's operation and processing efficiency. So, disc-caching is bad and maximum RAM is good.
Data requires storage--you need a place to keep all your music files as well as the files used to run your computer. Most computers use hard drives for this purpose. Faster drives with larger on-board memory caches and higher rotation speeds are better for computer-music systems because they deliver data more rapidly and have more memory for error correction. Whenever possible, 7200 RPM drives are a better choice than 5400 RPM drives.
Recently silicon memory discs have become more readily available and competitively priced. These silicon static-memory drives use less electricity and generate less heat than conventional hard drives because they have no moving parts. For some applications, such as storage of digital music files, they are superior to conventional hard drives since they have faster access times and lower numbers of read errors. But in situations where data must be written, retrieved, and rewritten over and over again, such as in your main computer drive, silicon discs aren't the best choice. Silicon drives have a finite number of times that they can be successfully written and erased without write errors increasing. In short, silicon drives make excellent data drives but not optimal operating drives.
So far the largest commercially available silicon drives are only 320GB, which may be too small for the largest computer music libraries. But for many users 320GB silicon drives make an excellent choice for storing music files. On my Dell D620, for example, I have the option to use a standard internal drive for my operating system while storing my music files on a silicon drive mounted in a removable drive sled that goes into the slot that normally holds a CD-ROM drive. This rig makes a fine portable and completely self-contained music server.
Even the most conservative and untweaky audiophile should realize that for better or worse, cables have an audible effect on sound. Just because a music system is computer-based doesn't mean that cabling will suddenly be any less important than in a conventional system. Unfortunately many owners of computer-based systems put little energy or resources into their cable options. Regardless of whether you employ USB or FireWire between your computer and other external sound devices, I would recommend never using the free cables that come with your external hard drives. The least expensive cables I use are the Belkin Gold Series USB and FireWire cables. In my computer audio system I've been using the Belkin Gold USB cables with excellent results. A serious step up from the Belkin Gold is the Locus Designs Polestar cable. In almost every setup where I've substituted the Polestar for the Belkin Gold I've found the Polestar delivers a noticeable sonic improvement.
Many computers use standard IEC AC cable connections. Experimenting with higher-grade AC cables can have beneficial sonic results. Just as with conventional audio components an AC cable that delivers superior filtering and/or isolation capabilities can improve the overall sound of a computer-based system. [The sound of my PC-based server improved noticeably after replacing the stock AC power cord with a mid-priced cord from Shunyata.--RH]
Never plug a computer directly into your AC wall outlets. Computers are highly sensitive to all forms of AC power anomalies--surges, brownouts, sudden power losses can all wreak havoc on a computer's sensitive circuitry. Computers need to have at least a UPS (uninterruptable power supply) unit with spike protection so that if you have a power problem your computer won't shut down mid-operation, leading to corrupted files. If you do suddenly lose AC power, it's important to have the opportunity to shut down a computer correctly to avoid future problems.
In a computer-based audio system you should also try to isolate your computer's AC from the rest of your system. That's because a computer's power supplies can have an audible negative effect on the rest of your audio system. I recommend keeping your computer on an entirely different circuit if possible. If that's not feasible, isolating your audio components from your computer with a brickwall power protection/conditioning system such as the PS Audio PowerPlant Premier will prevent the digital switching power supplies in the computer from dumping noise into the rest of your system. My own AC power line tests have shown that my Dual Core Xeon PowerMac does produce some AC noise. Currently I use AudioQuest NRG-3 AC power cables for all the audio components in my system connected to a PS Audio Quartet power conditioner to isolate them from my Mac's AC power noise.
USB, FireWire, Coaxial, TosLink, Oh My!
You can find a plethora of conflicting information on which method is best for connecting your computer to an outboard DAC. Advocates of FireWire argue that since it's been the professional standard for a number of years, it's also the best option for high-end consumer-audio setups. USB proponents point to the ubiquity of USB and the ease of setup. Coaxial boosters write about coaxial connections having the lowest inherent jitter rates. Finally, TosLink fans point to the complete galvanic isolation between computer and the rest of your audio chain that only TosLink offers. So what's an audiophile to do?
All of the points made in the paragraph above are valid. And, frankly, there is no clear-cut universally sonically superior method for connecting your computer to a DAC. In every system other variables, such as your software and hardware choices, will make a profound difference in which method is sonically the most advantageous. Also the only way to know which will work best is by trying each connection and listening to the results. Alan Taffel found in the systems he tested that coaxial and FireWire were optimal. I've found that in some configurations TosLink or USB produced the best results. My advice is to try all your options and don't make any final decisions until you've finished listening critically. The old cliché, "Your mileage may vary," was never more appropriate.
When your computer is in one room and the rest of your audio system is in another you usually have more than one way you can connect the two--via wired Ethernet or wireless WiFi. Sometimes physical restrictions such as distance, layout, or the physical makeup of your home will be decisive in determining which method is most practical. In terms of fidelity each method has its appeal. Hard-wired connections offer more robust data throughput and are less likely to suffer from dropouts and data loss. Wireless connections allow your computer to be completely isolated from the rest of your system, which can eliminate any noise problems caused by AC, RF, and EMI.
Once again, since each connection method has its own particular advantages and disadvantages it's impossible to make a blanket recommendation about which is sonically superior. I've used both wireless and hardwired connections with my computer audio systems and found that wireless connections are definitely more prone to dropouts, but the complete isolation between the computer and the rest of my system is comforting. The best solution is to try both connection schemes and then choose the one that combines more ergonomic and sonic advantages.
Just like the arguments about whether nature or nurture is most important to human development, the discussion of whether software or hardware is more critical to sound quality in a computer-based audio system will probably continue well into the foreseeable future. Obviously not only does your choice of playback software have a major impact on the sound quality of your computer-based audio system, but how that software interfaces with your hardware will also affect your hardware choices. Just because one user finds a particular piece of software produces optimal sonics doesn't mean that you will have the same results in your system. Sometimes software decisions won't be clear-cut. When forced to weigh ergonomic ease against ultimate sound quality, different users will make different choices based on their own priorities. While iTunes is convenient, it doesn't offer (and doesn't claim to offer) the best playback quality; however, improving upon it does require additional effort in setup and day-to-day operation.
Simple Ain't No Fun
Probably the most often asked question I've heard during 30-plus years in audio is the query, "Which is the best?" I despise this question because it means that someone wants a simple solution to a complicated situation. The art and science of high-end audio has always been about exploration and discovery. Computer-based audio is no simpler than high-end audio. Fortunately, the more you explore and the deeper you dig, the more sonically rewarding computer-based audio becomes. We are only at the very beginning of what will be known as the "computer-audio age." It will be a wild but entertaining ride.