Hi @ttako, yes, there’s something that could be done here for sure. There is a side project using RC notch (like on QA480) and RC notch for a resonator that is being studied for getting THD+N to -125 dB or so to measure some of the newer class D amps that have THDN around -118 dB or so. Some of the requirements are listed at the link below. Soon there will be an update. If it works at 1 kHz, then the question becomes if it’s useful to test at other frequencies and a tracking notch as you mention becomes interesting for sure.
1 Like