Discuss The Viv Lab Rigid Arm

@lewm 

With the program I use, you snap a line exactly parallel to the cantilever then another through the long axis of the stylus. It should read 90 degrees. All my current cartridges are 90 degrees within the error of the process. I just started doing this recently. But I have seen cartridges that were obviously off by eye.

As for TAE as the stylus rotates off tangency it reads the groove at a slightly different time in one channel than the other, phase shifts. The higher frequencies have much shorter wavelengths and consequently shorter groove modulations. Thus with TAE you are going to shift phase much more dramatically for high frequencies. At 180 degrees the channels cancel eachother. This will happen a lot sooner for 20 kHz than it will for 20 Hz. You actually cannot shift phase enough at 20Hz to make any significant distortion because the wavelength is so large in comparison to the size of the stylus. You can't even shift phase much more than a few degrees at 20 kHz as the wavelength is still significantly larger than the stylus.  

The phase argument was originally yours. I don’t buy its importance either. We agree.

Hey all,

Another problem I am having with this discussion is the term 'distrotion' is being used way too generically.  I believe that the original use of the term by Löfgren etal was referring to THD caused by having a HMA (horizontal modulating angle) different than the HTA (horizontal tracing angle).  In his AES convention paper, Richard Tollerton digitally simulates errors of VTA and HTA in reproduced music and concludes large errors (beyond what an underhung arm provides) are required to enter the realm of audibility.  This is in direct contrast to my experiences and as far as I can tell Tollerton only considers the effect of the relation of the cantilever in the horizontal and vertical planes and like the pioneering work does not include the effects of incorrect SRA or Zenith.  

I find vinyl playback to be an inherently high measured distortion medium and any numbers predicted by the various alignment types tend to be of such a small comparative magnitude that much of this discussion is about the mouse and not the elephant it has trapped in the corner.

dave

@intactaudio 

If the mouse is distortions fromTAE, what's the elephant?

the elephant is every other thing about vinyl playback that obscures the ability to measure minor changes in THD as a result of TAE.  Attempting to assign an accurate and consistent FOM to TAE from THD has thus far proven to be an effort in futility.  An interesting addendum to this is how many people take the theoretical numbers rooted in the conceptual world and argue about the superiority of one alignment vs. another without a clue as to how their cartridge is actually aligned in the real world.  I think it can be summed up with my belief that if you have two null points on the record face then you have won and bet far greater than half of the folks out there do not have any null points.  For reference, based on the goal of an ideal Löfgren A a TAE of ±0.8° will push the null points off the playable area of a record.

dave