Final post in my response to your thoughts...
I agree with your point about “beam” protractors versus arc protractors but you can also add the problem of stacked tolerance error that beam protractors are subject to.?
Here is the biggest issue I have with measuring electronically for a mechanical transcription system (a.k.a., turntable): test records themselves.
It is obvious that recording engineers can have a misaligned cutterhead, misaligned cutting stylus, misaligned sled or even an asymmetric cutting stylus (we see plenty of those!). However, they are equally likely to err clockwise versus counterclockwise against their targets. Further, we KNOW those targets or their target ranges (“ranges” in the case of cutting stylus rake angle and vertical modulation angle). The whole WAM Engineering effort is aimed at getting our playback stylus and cantilever to hit those targets. If we have a test record to use as our fiducial to hit optimal targets we are implicitly trusting the recording engineer of that test record to have NAILED all of their targets and to have used a perfectly symmetrical cutting stylus. More variables!
So how do test records do in this regard?
We have a growing stack of laboratory test records (now about 11” high) that we use for our tests but we leaned pretty quickly that the test records have errors of their own and we would need a way to measure those errors so we could net them out of our results so we could better run a worthwhile set of experiments. Since I could write a great deal on this subject I’ll limit it to CUTTING ZENITH ERROR and cut to the bottom line.
We have optically and electronically measured square and sine wave grooves in the vaunted DIN, NAB, CBS Labs, Denon, JVC, and more and found cutting zenith errors of as much as 4.25 degrees.
?So, if you are going to trust any given test record as your fiducial as true and accurate with regards to its fidelity to the engineer’s alignment goals, how do you know they have been attained? What procedures are written in the liner notes to assure you the engineers have taken all possible measures to do so and that they KNOW their own margin of error?
More variables. You also have to wonder about the algorithmic variables from software. We struggle with that frequently as we have seen that as we computationally filter and average data we can get variable results. We can even “force” the data to tell is what we want to see. Dangerous!
In our opinion, the proper way to make a test record is to communicate HOW we confirmed everything was dialed in perfectly so that you could trust the engineer and his work. The engineer should share his margin of error to demonstrate that all variables were properly managed.
By the way, it is not possible to use the same track to optimize for SRA and VTA. SRA is most sensitive to horizontal modulations and VTA is sensitive to vertical modulations. They are both important for different reasons and though they cannot be adjusted independently, there is a balance to be struck. The research on this balance has never been done, much less published, as far as I can tell. In fact, though a great deal of work has been done on ideal VTA, next to nothing has been done on SRA. Generally speaking, cartridge manufacturers have WAY too high VTA (scientists and research engineers have been complaining about this since papers published in the early 60’s) so the lower, the better - particularly for some brands of cartridges. I think there has been a collective amnesia or willful ignorance amongst cartridge designers to fully understand the cost of a high VTA. The manufacturers enjoy benefits for kicking it high up. Audiophiles don’t. ?
So, I hope I have made it clear that the WAM Engineering system takes into account DYNAMIC play for its alignment procedures and the variables which exist are known, measured and controlled for. One cannot say that about use of a test record as a basis for cartridge/ tonearm optimization for which the variables are not known or shared which allows us to infer that they are not controlled for.
If I did not address any of your points, please let me know. I certainly appreciate that you think deeply on these topics. Whether we agree with each other isn’t important. People like us push standards upwards and that benefits many.
