I had one extra set of parts, and I gave that to a good friend - he lives on the other side of the world! - because he wanted very much to make one for himself. I don't plan to sell this is a product because it's too limited in what it can do. I did publish the most important parts of the schematic in an article for audioXpress magazine, and that article should be online in a few more weeks. I may just post the entire schematic at some point if anyone cares. The main problem is the meter driver doesn't work quite right, so I'd have to spend time fixing that first.
Nice cat. FYI, I own a couple of your RealTraps, though I retired before I could afford to spend for more, so the system will just have to do as it is.
I found your youtube video about the null tester. Brave man. I have seen plenty of "discussion" on the subject of cables, and can appreciate why you wind up in some people's gunsights. For example, Litz wire speaker cables, indeed! I also encountered a video about a brand of cables from Australia who package a bottle of 'snakeoil' with their cables - along with the disclaimer that it's a joke, and if you order 'snakeoil' from their website, you will receive a small bottle of tapwater for your $998.
However, while I understand what you are trying to accomplish, I can't help but wonder whether something like a square wave input (theoretically an infinite series of sine harmonics, as you know from your mention of Fourier) might be a better choice than a 400 Hz. sine. Clearly, you can prove that a pair of cables performs the job at that frequency, but the act of obtaining a null implies an electrical difference between the two cables. Given the differing reactance of the cables you tested, I should think that the performance over the audio band ought to be different (then there's EMI). Just given the change in capacitance between 16 pF and 94 pF per foot, I'd expect about a 0.15% change at 20 kHz. Further, looking at the roll-off of the square waves should also be enlightening if you can get your scope probes capacitance well below the cable capacitance (I have a pair of really old Tek probes that claim 6 pF.).
My thought here is that the golden ear types could claim that they hear that difference. Further, I've noted a new 'specsmanship' war. The claimed frequency range of AV components seems to keep climbing - 100kHz. top end is not so unusual now (which I concur could be described as poor design), so I wonder about RF influences on the preamps/amplifiers. It seems to me that if enough energy was getting into the inputs at frequencies above the audible range that the headroom of the system would be affected, no? That might lead to random increases in distortion levels in the AF band, I should think, due both to overhead limits and harmonic distortion.
Caveat: I have XLR cables between the preamps and mostly monoblock amplifiers in my system due to lengthy runs. I now use Mogami, but do NOT claim this is change to be of any sonic benefit over the Monoprice, et al cables I started with, but mechanically they are much more reliable. I had more than one of the cheaper cables develop poor connections. As I recall, you also commented on termination issues in your video.
Did you not watch the entire video? Most of the test was done using full range music. The 400 Hz tone was just used at the beginning of the live portion to show what nulling is. I also show the response of the tester to well past 20 KHz.