theophile, For those who are adherent to the gospel about minimizing tracking angle error (TAE) at all costs, the terms "distortion" and TAE are interchangeable. In other words, they (and apparently you) use the two terms as synonyms, where TAE is a subset of all causes of distortion. So it is no wonder that the Radiotron book conflates the two terms. But overhung tonearms with headshell offset trade off low TAE for a large increase in skating force, and a skating force that changes in magnitude, up and down and up, etc, across the surface of the LP. In 1940, when Baerwald, Lofgren, etc, published their papers on overhang and offset angle, they were just solving a geometry problem. They had no knowledge of stereo or modern stylus shapes (all styli were spherical) or even vinyl records. The majority of music lovers were still using wind-up "Victrola"s to play mono shellacs in that era. You have to ask yourself, could it be that skating force (and the application of Anti-Skate) is more pernicious than TAE, or at least similar in its negative effects, for the performance of a modern cartridge with an exotic stylus shape trying to produce a stereo image from information encoded on the sides of a V, rather than on the floor of a mono 78? Furthermore, the underhung tonearm with no headshell offset angle does give a single null point where there is also no skating force at about the midpoint of the LP surface; at that moment, the underhung tonearm behaves exactly like a linear tracker. Immediately before and after that null point is reached, the TAE is actually in the same ball park with that of a conventional overhung tonearm, with the added benefit of much lower skating force. So knowing all that, is it so preposterous to think that there may be some merit to the idea of an underhung tonearm? I own two copies of the Radiotron Designer’s Handbook, and I have learned from the book often in studying circuit design, but in this case their heads are or were in the sand, in my opinion.
For me, the most glaring fact is that the naysayers say an underhung tonearm properly set up would be a disaster with high distortion based only on TAE. If you listen to such a tonearm, the very first thing you would absolutely have to admit is that there is NO such disastrous distortion. This is regardless of whether you go on to love the tonearm or not. Doesn’t that simple observation make you want to think more? If not, I cannot help you.
Oh and by the way, I always forget the fact that most cartridges have some zenith angle error. This is error in the way the stylus is mounted on the end of the cantilever. An imaginary line connecting the centers of the two contact patches on the stylus tip must be perpendicular to the groove walls. If there is any deviation from that standard, then all your or my best efforts at alignment according to any algorithm are for naught. Turns out that the few companies that make all the cantilevers and styli observe a +/-5 degree standard for zenith angle error. Even a one or two degree error will screw up Lofgren, etc.
