QA402 Feature Request

[matt]

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.

Measuring A Modern Discrete Class D Amp

The QA402 can readily measure the performance of modern class D chip amps, even with them surpassing conventional class AB amps. See here and here and here for examples. But some of the newer Class D amps from companies like Purifi are re-defining what high-performance means from a measurement perspective. Let’s take a look at some of their published specs and see what it might mean if we wanted to measure with at least some margin. First, we have the following table from their website. The tw…