A new white paper from Audio Precision, written by Joe Begin, director, applications and technical support (recently retired), discusses the critical nature of grounding relative to automotive audio systems. It concludes with details related to the filtering of Class D amplifier output signals prior to arriving at the analyzer inputs.
The application note provides a comprehensive overview of the testing typically done on automotive audio power amplifiers, describes which standards apply to the individual measurement methods, and demonstrates what the results should look like for the commonly performed measurements.
The full version can be downloaded here.