Preparing loop-back

A loop-back is a physical connection from the output to the input of the sound card as shown in the figure below. The MLS output signal is always played in the left channel and the loop-back output signal is played in the right channel. Connect the cables as shown in the figure below,

Figure 5 Schematics for one-channel measurement using loop-back

You might need to purchase extra cables to be able to connect the loop-back.

If the input you are using for the microphone signal is mono (the microphone input is usually mono), no right input channel exist. Then connect the loop-back input cable to the right channel input of the line input instead.

Open Measurement->Sound Card Settings dialog box. Make sure ‘Yes, with loop-back and end-check’ is selected as shown in the figure below.

Now select the Loop-back Input Line you used for connecting the loop-back to, in the figure above Line-In is chosen. Make sure Loop-back input channel is set to Right.

The sound card delay must now be set in samples, this we already have found in the first measurement procedure we described. This number can vary from 10-80. After typing this number, click OK to exit the dialog box.