I’ve been reading Arto Kolinummi’s book about audio amplifiers. He devotes a lot of pages to the subject of memory type distortions. I’ll quote him from his book:
“This type of distortion can be characterized as memory distortion because it is based on stored energy which is released with some time constant causing an error after the offending signal has passed through the system. Energy can be stored in various ways such as heat, charge, or mechanical energy. Memory distortion error can be totally invisible in distortion tests with steady state input signals.”
I’ve been trying to figure out how to measure this.
One approach would be input a pulse of some kind and then measure the resulting harmonic spectra over time. That’s how a lot of loudspeaker measurement programs work. They call the output “cumulative spectral delay”.
That would be a nice solution, but I’m not sure how to do that with a QA401.
Another approach might be to capture the peaks of a spectral plot, where a lot of cycles are captured at their peak, instead of their average. Kinda like a Max Hold or Peak Hold on a spectrum analyzer. The opposite of averaging. (I think it’s the opposite…) This might also be valuable in measuring DACs, since some of the processing within a DAC is hardly synchronous with the applied tones, so various products might appear on a random basis that average out over time.
This probably means that a different software detector or faux window process is needed to capture and hold peaks.
The function is described here: http://www.w7ay.net/site/Applications/Amici/index.html
Are these functions that could easily be rolled into the next great rewrite of the software? Please? Or, will the new platform be flexible enough for somebody to add these on their own?