When you record the sounds input from Line-in, and in the mean time you listen to the recording from the speaker, you may find 0.5 to 1 second delay.Consider the following scenario:You are musicians. When you plug the headphones into the computer and listen to music, then plug the guitar in the microphone jack and enable the microphone sound output so you can play along with the music, the computer is acting as a mixer.
With Windows 7, the mic in output has quite some delay, between 0.5 and 1 second.
Not all drivers expose the hardware loopback. In addition, some IHV drivers no longer expose the hardware loopback since Vista and Windows 7.
Please contact your sound card vendor to seek this option.
Please reference the following forum thread: