How to perform relative calibration of mixer input levels?How to calibrate the input of the measurement system?
The purpose of calibrating the input is to be able to measure absolute level (input level absolute calibration) and to obtain the true transfer function gain independent of the level of the WinMLS mixer input (relative calibration of mixer). The calibration can be done in different ways dependent on the features of the sound card (e.g if the sound card supports the WinMLS mixer or not) and the type of measurement you intend to perform. For some sound cards, e.g. VXPocket, a measurement setup file will be available with nominal calibration settings.
If the sound card input and output is calibrated, a MLS measurement should give an amplification of 0 dB for a loopback measurement (input directly connected to output). If also the mixer is relatively calibrated, the gain should be independent of mixer settings (changes in mixer settings will not change the gain of a loopback measurement).