Q. On the back of my sound card I have several different jacks. The manual describes them as speaker, mic, line in and line out, but that’s about all it says. I understand the speaker and mic parts, but what exactly are line in and line out? Isn’t line out the same as the speaker? And line in the same as the mic? If not, how are they different? Would I be in trouble if I plugged extra speakers into the line out jack?
A. You would not be in trouble if you plugged speakers into the line out jack. You may not hear much, though.
The line out is an unamplified output from your sound card. In many cases this is used as the primary connection for a set of amplified speakers. It can also be used as an output to a stereo receiver for the purpose of sending sound into your stereo system for listening and or recording.
An amplified signal can cause distortion and even damage if sent to an amplifier like the one in your stereo receiver. Most sound cards have a built in amplifier, ranging from 1 watt to 5 watts.
The line in jack is a secondary input on your sound card and is used for bringing in an unamplified signal to your computer. Like from a cassette deck or a phonograph.
You do not want to bring an amplified signal into your computer as you can easily damage it by doing so.