Sound Card Features and Functions
The motherboard on most computer systems has an integrated sound card, which is often sufficient for many users. However, to get higher quality sound you can upgrade to a separate sound card, which uses better and more expensive components.
Audio files on a computer consist of digital data just like any other file on a computer. Sounds we can hear consist of waves that travel through the air - sounds are analog. The primary function of a sound card is to translate between digital and analog information, just like a video card. Sound cards typically have four major components:
- The digital-to-analog converter (DAC), which makes it possible to convert digital data to analog sound
- The analog-to-digital converter (ADC), which makes it possible to make digital recordings from analog sound inputs
- An interface to connect to the motherboard, typically using Peripheral Component Interconnect (PCI)
- Input and output connectors so you can plug in headphones, speakers or a microphone - many computer systems have speakers and microphone built-in, but connectors allow you to use higher quality external devices to play or record sound
On some sound cards, the two types of converters are integrated into CODEC a single coder/decoder chip. Some sound cards also have a digital signal processor (DSP), a built-in processing unit. The DSP takes some of the load of the central processing unit (CPU) to convert between digital and analog. Similarly, some sound cards have their own memory. Sound cards without a DSP or memory will use the motherboard's CPU and memory.
Computer systems typically have built-in speakers, which are reasonably good if you don't turn up the volume too high. If you want to use your computer for some serious music for a party, you probably want to connect a set of external speakers. Relatively small external speakers can be powered using a USB connection, while larger ones need their own power supply. Similarly, most computer systems have a built-in microphone, but you can also connect an external microphone.
Serious audiophiles who use their computer as their sound system will typically upgrade to a high-end sound card, a set of good external speakers, and a good external microphone (if they want to make their own recordings). A high-end computer system can rival dedicated music equipment. In general, with the improvements in sound and video, computer systems have turned into multimedia systems rather than simply computing devices to run software.
Connectors
You can use the computer's internal speakers to listen to audio, but what if you want to plug in a headset or set of external speakers? Several types of audio connectors exist. These are 2.5 mm mono, 3.5 mm mono, 3.5 mm stereo, and 6.35 mm stereo.
The 3.5 mm connector is by far the most widely used type for computer systems as well as other portable electronics. The larger 6.35 mm connector is used mostly in dedicated audio systems, such as electric guitars, loudspeakers, and microphones. These types of connectors have their origin in telephone switchboards and are therefore sometimes referred to as 'phone connectors'. More commonly, they are also referred to as audio jacks.
What about external microphones? Most use the same 3.5 mm connector as external speakers. As a result, some sound cards have quite a few identical looking connectors. This gets confusing, so a color-coding scheme was developed. For example, the color-coding might appear as follows: pink for a microphone input, light blue for an analog audio input (other than a microphone), light green for the main stereo analog audio output, and orange for a center channel speaker or subwoofer.
So how does stereo work using a single connector? Take a closer look at a 3.5 mm audio connector. Notice the two black rings?
Technically, this is called a TRS connector, for tip-ring-sleeve. The two small black rings serve as insulating rings between the tip, the ring and the sleeve. The tip corresponds to the left audio signal, the ring corresponds to the right audio signal and the sleeve serves as the ground.
A similar logic applies to external microphones. For a single microphone, the tip is used for a mono input signal. When left and right microphones are used, the tip and rings serve to record a stereo input signal.
So what about some of those smartphone models that have a single connector for stereo sound and a microphone? These use one more ring and the connector is therefore called TRRS, for tip-ring-ring-sleeve.
While the 3.5 mm connector remains pretty standard on most computer systems, many newer types of external audio equipment use a USB connection. For example, if you buy headphones with a built-in microphone it will typically come with a single USB connection rather than two separate plugs. On newer laptops with a built-in microphone, you will often no longer find a separate microphone input connector.
Lesson Summary
A sound card converts between digital data and analog sound. This allows you to listen to music and record your own sound. Different types of connectors on a sound card allow you to use external devices, such as headphones, higher quality speakers, and a microphone.
Learning Outcomes
This lesson on sound cards should teach you to:
- Define 'sound card'
- Describe the functions and features of sound cards
- Consider what connectors may be needed to listen to audio
