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Why buy an Add-on Sound Card?
Onboard or Add-On?
It's no wonder that the introduction of integrated audio into the market, caused a significant downfall in the sale of add-on sound cards. In fact, why shouldn't it? The average user doesn't need to spend an extra $20 - $40 to hear the windows "beep" better. The newer motherboard models feature the 7.1 surround sound in 3.5 mm jacks, High Definition Audio (HDA) cable, and feature a decent Signal to Noise Ration (SNR) at a decent sampling rate.
First, lets find out what exactly the technical terms mean. Signal to Noise Ratio (SNR) is a ratio of signal strength over noise strength and is measured in decibels (dB). A decibel is a measurement of power of intensity. In other words dB is a measure of a power of 10. When saying signal A is 10 dB stronger than signal B, in actuality that means that signal A is 10 times stronger than signal B. If signal A is 20 dB stronger than B the A is B times 100, 30 dB would be B times 1000 and so on.
The general idea is that add-on sound cards produce better sound. The first question that comes to mind is what does "better" mean? Better is a relative term but for the sake of professional and commercial recording, sound cards that have a SNR higher than 110 dB are considered to be high quality. This means that the strength of the signal is more than 100 billion times stronger than that of the noise. Lower end sound systems have a SNR of approximately 90 dB, or have the signal 1 billion times stronger than the noise. In comparison, standard CDs provide about 100 dB SNR and Cassettes provide around 60 dB SNR. Although the differences in the dB range are miniscule (only 20 dB) between what would be considered high end and low end, have in mind that since we are using powers, the differences are noticeable. Also, have in mind that 160 dB more or less is the limit of human hearing. There is no set standard for high-definition audio decibel-wise, anything that is capable of producing more than 110 dB SNR should be considered high quality equipment and as such, carries a hefty price tag. The reason why add-on sound cards tend to have a higher SNR is because they are located away from the main chipset's such as the processor, north bridge, south bridge, ram, etc which create signal interference which translates to more noise in the output.
A major factor contributing to the calculation of maximum SNR (more is better) is Digital Audio Depth or sometimes referred to as Digital Bit Depth. Digital Audio Depth can be found as one of the specifications on almost every sound card out there. As a rule of thumb, 6 decibels are allocated per every bit. A sound card that has Digital Audio Depth of 16 bits will only be able to produce a max of 96 dB SNR, where as sound cards that have Digital Audio Depth of 24 bits will be able to produce a max of 144 dB SNR. Please note that Digital Audio Depth only determines the theoretical limits, just because a sound card uses 24 bits doesn't mean that it will perform at 144 dB SNR.
Sampling rate is another major component of sound equipment which determine its quality. It is a typical assumption that in order to be able to reconstruct a signal perfectly the sampling rate has to be higher than twice the upper band limit of the sample that is being played. This means that if you would like to play a song where the maximum frequency at any given time is 20 KHz then equipment with at least 40 KHz sampling rate is required, thus leading to the ever-so simple conclusion: "More is better". The high end media such as Blu-Ray disks and DVD's usually produce 96 KHz to 192 KHz output. To experience highest quality of sound, high quality sound card is required.Lets take a quick look at a comparison.