Now that you have a computer with your music inside and music software to play the music, you need to get the music to your audio system. One way is to put a digital-to-analog converter (DAC) card in the computer itself. Often called “sound cards,” these devices usually offer not only analog outputs but digital outputs as well. Many PC soundcards even support 5.1 or 7.1 analog for home-theater applications. The disadvantage of soundcards is that most were designed principally for gaming PCs and many use inexpensive DACs.
Some soundcards do have good DACs and excellent specifications, such as the $175 Asus Xonar Essence STX (usa.asus.com/products.aspx?l1=25&l2=150). This card features 124dB signal-to-noise, has a built-in headphone amp, and supports 192/24-bit files. It uses a Cirrus-Logic CS53811 ADC, and has swappable op-amps in the analog section, so you can try different ones to suit your tastes. It also employs extra shielding for the analog section to reduce the effects of electronic noise in the computer’s chassis. Unfortunately for Apple users, it’s only available for PCs.
A pro audio sound card such as the $675 Lynx L22 PCI card (lynxstudio.com/) supports high-definition music files and has additional shielding to protect it from the computer’s electronic environment, but obviously it costs substantially more than basic consumer cards. The good news for Mac users is that the Lynx card works in both Macs and PCs.
A second option is use an external DAC with a USB connection. Every modern PC and Mac computer has at least one USB output connection. USB DACS start at as little as $99 for a High Resolution Technologies MusicStreamer (highresolutiontechnologies.com). The MusicStreamer sounds remarkably good and is capable of decoding up to 48kHz/16-bit music files. On the other end of the price spectrum, Empirical Audio (empiricalaudio.com) makes a suite of products designed to work together or individually, including a dedicated USB DAC called the Overdrive DAC with USB ($3699 base price), an Off-Ramp USB converter so you can use S/PDIF DACs with USB-enabled computers ($699 base price), and a Pace Car re-clocker ($1250 base price) which is designed to reduce jitter from S/PDIF sources. Most USB DACs are limited to 48kHz and 16 bits. But there are some exceptions, such as the $495 Bel Canto 96/24 USB converter (belcantodesign.com), which converts a 96 kHz/24-bit USB stream to a S/PDIF coaxial connection. In the future even more companies will be offering higher resolution USB DACs.
Another option is to connect either a coaxial or optical/TosLink S/PDIF output from your computer to an external DAC. Apple offers optical TosLink outputs on every computer it makes. For PCs, soundcards can be installed that will supply coaxial and/or TosLink digital outputs. The nice thing about S/PDIF outputs is that they readily support higher bit rates. You can begin to enjoy higher definition (above 48kHz 16-bit) music files merely by connecting a DAC that supports these higher resolution files to the computer’s S/PDIF output. Some audiophiles believe that coaxial connections are inherently sonically superior to TosLink due to coaxial’s lower jitter. But a TosLink connection permits complete galvanic (electrical) isolation between a computer, which can be a source of EMI, power supply, and AC noise. This noise can affect the rest of your sound system. Whether one connection method is sonically better than the other depends as much on the other components (both hardware and software) in the system as the connection itself. Unfortunately for audiophiles who don’t want to experiment, can you only reliably determine which connection is sonically superior in a particular system by direct comparison.
The IEEE 1394 FireWire digital connection comes from the pro audio world, where it has been the standard for several years. All upper-end Macs are equipped with several FireWire connections. FireWire adapter cards can also be easily installed in any PC. Most FireWire devices include multichannel ADCs and DACs along with a multiplicity of analog and digital inputs and outputs since they were made for recording. But some FireWire audio devices were designed for two-channel use only, so they have fewer features. Market-leaders include the $495 Apogee Duet, $895 Mini-DAC, and $249 One (apogeedigital.com). Focusrite (focusrite.com) makes two reasonably priced full-featured FireWire devices, the $349 Saffire and $299 Saffire LE. Both come bundled with very nice recording software.
While many pro audio companies, such as Mark of the Unicorn (motu.com), PreSonus (presonus.com), Mackie (mackie.com), and others, make FireWire recording interface units that can serve as DACs in a computer-based audio system, the majority come with dedicated software packages. However, most pro audio devices will work with consumer playback software such as iTunes merely by designating the unit as the sound-output device in your computer’s sound control panel. Occasionally you will have to hunt on-line for a needed driver. On rare occasions a manufacturer may not yet have a driver for the latest generation of your operating system. Buying from a retailer who can give you phone and on-line support as well as let you try out a card in your system is important in guaranteeing satisfactory final results.