TechTalk
LoopBack (Full Duplex)Test Details
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In the loopback or full duplex test, the wave input or sound recording portion of the sond card is tested in terms of its ability to accurately convert a ordinary audio signal from digital to analog and back into digital. This wave handling portion oof the card is tested as an Analog to Digital Convertor (ADC) and as an Digital to Analog convertor (DAC).
A test signal is generated digitally andconverted to analog (in other words, an ordinary audio signal voltage that has many possible amplitudes and varies with time) using the Digital to Analog Convertor (DAC) on the card. This signal is converted back to digital using the Analog to Digital Convertor (ADC) on the card.
The digital output of the sound card is evaluated for distortion and noise by digital means. In actual use, the output of the sound card's ADC would proably be recorded as a wave file. Depending on the Distortion and Noise Analyzer used, we operate the card under test direcctly, or we analyze a wave file made by the sound card and reference wave file recorder software.
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