Although a laptop includes its own sound system, many users need larger and more powerful ways to pump up the volume. If you don't want to settle for the audio equipment your laptop comes with, you can plug in external audio equipment by using the jacks on your laptop.
All current laptops include facilities to get sound in or out of your laptop. Some hardware is better than others; consider the options when you buy or upgrade your portable computer.
Jacks are holdovers from the early days of electrical devices, a system to easily bring together open ends of a single wire, or perhaps two or three, in a temporary connection. Remember pictures of telephone operators connecting an incoming call to its intended recipient? The operator held a jack with two wires, separated by an insulator, and looked for the appropriate receptacle that could pick up the two signals. On computers, jacks and matching receptacles are used for simple circuits, such as audio for speakers or input from microphones or amplifiers.
Microphone jack
The input for an unamplified microphone is the simple sort of device you use with a small tape recorder. Most laptop computers offer a female connector that works with a 1/8-inch monaural (single channel) plug, although some may work with a stereo (dual-channel) plug.
Experts say the best type of microphone for a low-voltage circuit, such as the one on a laptop, is generally an electric condenser design. If you connect a dynamic microphone, another common design, you may find that the sensitivity or volume level is lower than you prefer.
Consult your instruction manual for any unusual specifications for your laptop. You may find some laptop makers specifying the use of a 3.5mm plug; in most cases, that metric size, though not identical, is close enough to work with a 1/8-inch plug.
If your laptop permits use with a stereo plug, consult the manual to see how it handles a mismatch. For example, one model of HP Pavilion laptops with a stereo port advises that if you use a monaural microphone, the laptop will record the same information on both channels of any file you create.
Headphone jack
The miniature socket here (on most laptops designed to mate with a 1/8-inch or 3.5mm plug) outputs an audio signal you can use with personal headphones.
The best sound quality comes with headphones with an impedance of 24 to 32 ohms; impedance is a measurement of a form of resistance to the flow of electricity. What this means to you: Use a lightweight, low-impedance headset, such as those specifically designed for use with portable music systems, rather than one of those heavyweight professional-style headsets you may have for your home stereo system. You'll get better sound, higher volume, and longer battery life.
The same signal can also be directed to a set of external amplified speakers or accepted by some external stereo systems or television sets; these external devices need to amplify the signal by using their own electronics and power supply.
On most systems, plugging a headphone or other type of audio cable into the socket automatically disables the laptop's tiny internal speakers. To protect your hearing, always adjust the volume level before placing headphones on your ears.
Line-in jack
Some high-end laptops aimed at use in multimedia assignments (such as editing soundtracks) may have a line-in jack, which accepts an amplified audio signal. An example of this sort of signal would be the output of a stereo system, a portable audio device, or a tape recorder.
Consult the instruction manual for your laptop, and if necessary, an electronics retailer for advice on adapting your audio equipment or laptop for special recording purposes.
If your laptop isn't equipped with a line-in jack (or a line-out jack), you can purchase an external sound adapter that connects to the USB port.
Line-out jack
This socket delivers a lower-level signal that can be directly used by external devices with their own amplifiers, such as tape recorders, VCRs, and stereo systems. You can find line-out circuitry on certain high-end multimedia laptops.
