Choosing the audio I/O on your sound card

The current crop of sound cards normally let you choose how you connect your PC to your speakers. In the past, there would be only one audio-out jack on the card. It was usually a stereophonic output, so your PC could drive a pair of speakers using one single RCA coaxial cable.

Over time, as surround sound became popular, the sound cards began to have two pairs of analog audio-out jacks, one to drive the rear pair of speakers and another to drive the front pair.

Each of these channels could be adjusted separately using the software or the volume dials on the speakers' power amplifiers, so you can reduce the volume of the front pair of speakers and increase the power of the rear pair. The objective was to maintain the 3-D effect as realistically as possible in relation to where you are sitting among the speakers.

A subwoofer was also added to give more power to the lower frequency range. Because the lower frequency is generally non- directional, we normally need one subwoofer to produce a very powerful bass effect.

Then the digital audio channel became available on the sound cards. By being digital, the audio data is supposed to be immune to interference and you will be treated with a better quality of sound. It also allows for a configuration that consists of more than two pairs of speakers and a subwoofer.

The beauty of digital audio output is that you normally need a single coaxial cable to connect the sound card to the speakers. The standard is known as SPDIF (Sony/Philips Digital Interface). This four-channel cable requires a special RCA plug and jack, too. The plug has four separate contact rings, as opposed to the two you will find in a common stereophonic RCA plug. Some cards also support optical connection called TOSLINK to another device, but normally our speakers do not require it.

If you think setting up 5 speakers and a subwoofer is already a challenge, be aware that some sound cards support a 7:1 configuration. This means you can set up seven speakers and a subwoofer for your ultimate audio entertainment.

Some cards, such as the US$199 Delta Dio 2496 (24-bit, 96 KHz), only offer digital input and digital output. They are usually used in what is also called DAW (Digital Audio Workstation). You need these workstations when mixing audio tracks recorded in the studio -- usually using the Digital Audio Tape (DAT).

If you think $199 is already very expensive for a sound card, think again. LynxTwo from Lynx Studio Technology goes for $950. This professional sound card offers two analog inputs and six analog outputs, in addition to two-channel 24-bit/96kHz digital input/output.

And, if you are stunned by the fact that six analog outputs are available on this card, just hold your breath. The six analog output pales in comparison with the $279 Delta 1010 LT from M- Audio. This card provides ten inputs and ten outputs, 24- bit/96kHz capability with mic preamps, digital I/O, and MIDI I/O. Clearly, what you can do with these sound cards really depends on your imagination, and the sky is the limit.

However, for your everyday home PC, a more affordable sound card with a price tag well below $100 will do. Make sure it has both analog and digital I/O, just in case you want to transfer the music that you have recorded using digital devices to your CD. Also check other features such as audio enhancements technologies, such as Creative Labs' EAX. -- Zatni Arbi