The time spent is because of curiosity, It's not everyday that @atomicbob runs into amps that don't register any distortion on his dScope. Could be because the signal generator on the AverLAB is the cause of the distortion that we see on the AverLAB results, or that the dScope ADC doesn't have low-enough distortion to see it on its own, or there's some other reason attributable to the "measurements are hard" thing. Would be interesting to see AP-5xx measurements, which I am sure ASR will eventually provide. I've also gotten to the point where I feel I have a consistent methodology, cables, layouts, power outlets, loads, etc. to get repeatable results. For instance, I held on to headphone FR measurements for almost a year before even posting anything on the Internet. Little snippets is one thing, but you want to be sure before getting more into the game. You don't want to be that dude who is known for borking measurements or who is talking out of their ass (like Jude early on before he got schooled by others and then trained up by AP Jedi to take on Amir's borked linearity measurements.) Finally, Avermetrics finally released version 3 (beta) of their software which has usability improvements. I was hoping to get dual tone, IMD, or multitone, but for the time being, I am stuck with the Modi 3 as the signal generator. I can do most of the measurements, it's just that AP with their super software makes it x100 easier. It's not too different from ethical hacking. Nothing replaces a good penetration tester, but the expensive five-six figures pen test software makes it x100 easier and faster.