I have a question about using a sound card for doing distortion measurements. Using Visual Analyzer Visual Analyser I do a calibration with a loopback and then connect up my amplifier. Across the 8 ohm dummy load I have a 20k pot to attenuate the voltage to the line input to prevent damage.
Now the distortion figure changes greatly depending on the line in voltage. So what is the correct voltage to use? Perhaps what voltage the calibration uses?
Now the distortion figure changes greatly depending on the line in voltage. So what is the correct voltage to use? Perhaps what voltage the calibration uses?
Are you using a differential input on the sound-card? If not what is the grounding arrangment? Could there be non-linear ground currents causing the amp's output ground to not match the input ground?