Loopback Testing

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**WARNING**

Depending on the output levels of your sound card, looping the output to the input may overload and permanently damage your sound card hardware. Needless to say we take no responsibility for any damage. If you are not sure what you are doing, we strongly suggest you skip the loop back testing. We also strongly recommend you read your sound card documentation to determine if the output and input voltage levels are compatible. If you continue, read the precautions below in order to minimize the risk.

Method1: PassMark Audio Loopback Cable

loopbackcable1 loopbackcable2

The PassMark audio loopback cable can be used to make a link between the speaker output and the line in on the sound card. This can then be used to compare the output signal with the input signal and examine them for noise and distortion. PassMark audio loopback cables can be ordered online at http://www.passmark.com

Before connecting the cable adjust the output volume levels in the mixer to be very low. Turning down the volume in this way will limit the output voltage. This will lessen the risk of overloading the input. Once you have determined the input levels are reasonable you can increase the output level.

To start testing use the tone generator to create a test tone. The output wave form will then be displayed in the SoundCheck window. Start recording by clicking the circular record button or by selecting record from the menu. This display will then change to show the input wave form.

The wave form and spectrum can then be examined for distortion and noise.

Method2: Speaker to Microphone loopback

After making the correct settings in the mixer, place the microphone close to one of the speakers. This test as per the cable loopback. As you might expect there will be additional distortion visible using this method. This is because the speaker and microphone never reproduce sound perfectly. The amplitude of the sound will also be affected by the distance between the speaker and the microphone and the volume dial on the speakers.