This a rather wide-ranging topic. So a few points, my apologies if these have previously been covered
I collect linear tracking turntables and restore them to operational condition and best possible aesthetic condition. I have owned a B&O 4002 and two Pioneer PL-L1000A turntables from new. All servo assisted tonearms should just be considered a pivoted tonearm with a movable pivot point. Most of them track better than the eccentricity of the majority of LPs. I confirmed this a long time ago when I first got the B&O, I had the covers off tuning up the tracking and noticed the tonearm moved once a revolution at exactly the same radial position, that is, it was moving at the peak eccentricity of the LP. I found this occurred for the majority of the LPs I tried. So I discount the often cited problem of the stop start tracking and "crab walk across the LP" to no worse than any other form of tonearm. However, the linear trackers have other advantages, not the least of which is a much shorter tonearm with all the associated advantages. Aerodynamic bearing (levitated) and anti-friction bearing, passive tonearms are a totally different story, also not pretty.
There is little point in discussing turntable performance unless you first consider cutting lathe performance. Most late model, relatively high end, direct drive, turntables outperform the cutting lathes used to create the lacquer masters in W&F, rumble, speed accuracy, etc by a reasonable margin. I covered this is a posting in another thread some time ago:
Wow and flutter measuring equipment is probably near extinct these days, since no one outside of TT mfrs would use it. No digital format requires measurements like that, jitter notwithstanding. I doubt if TT reviewers have that equipment. Amazingly these apps work pretty well...
audiosciencereview.com
There are some subsequent posts in that thread that may be of interest.
Cutting head geometry compared to cartridge geometry and the effects of the mismatch is a very poorly understood area, this is before we take into account the mistraking of a cartridge that is not optimally adjusted. In many cases, there is no way of knowing the optimal setup of a cartridge. I once did a long thread on this subject over at Vinylengine, but one of the posters went off the deep end and the thread was frozen and now appears to have been deleted, a pity.
Anyhow, to put it in perspective, there were really only three cutter heads of two different geometries used to cut most vinyl. We can simplify this to two, the Neumann cutter and the Ortofon cutter (the other was essentially a clone of the Neumann). The Ortofon cutter used a very different mechanism to the Neumann. I do not know for certain, but I do not think that the Ortofon cutter head has been used by anyone for quite some time - they were very delicate devices. For interest, all CD-4 quadraphonic and half speed mastered records (CD-4 HAD to be half speed mastered) were cut by the Ortofon cutter head. All direct metal masters were done using Neumann cutters. Neither of these technologies was ever properly developed as they came too late in the game. Also of interest, both the Ortofon and Neumann geometries were first described in a single patent by the extraordinary Alan Blumlein who both invented stereo and made the first recordings in stereo. He tragically died during WWII in an aircraft crash while testing HS2 radar.
I will cut this short, the description of the Neumann cutter head and the issues it presents is a very complex subject, perhaps more at a later time. That is, more disturbing information about the cutting process for the vinyl purists out there to digest.
Bob
