SirSpeedy,
You must have been one of those AS was thinking of. Who else published the definitive guide to adjusting damping fluid in a Graham?! The dealers don't understand it 1/10 as well as you. AS is right, we have a great group here and we all learn as much as we teach.
Jim,
If you think about what we're trying to achieve in vinyl playback it's pretty simple. (To understand, not to do!)
We are attempting to exactly replicate the record manufacturing process, but in reverse. If our rigs could do that, with no distortion of any kind, then the signal coming from our cartridge would exactly equal the signal that went to the cutting head. That would be perfection in vinyl playback.
No rig can actually do this of course (except Rushton's!), but we seek to eliminate or reduce as many roadblocks as we can. One roadblock is this: the original lacquer was cut by a stylus whose profile was thinner and whose edges were sharper than ANY playback stylus.
Therefore, every decent LP has modulations cut into the grooves smaller than the radius of any playback stylus's contact surfaces. Even the best playback stylus cannot "see" all the musical information that's there.
What to do? Clearly, if accurate reproduction is our goal we must use a stylus that can read as many of these fine modulations as possible. Different stylus profiles will directly affect the accuracy of our playback.
CONICAL (sometimes called spherical, incorrectly)
These are shaped exactly as the word says, like a small ice cream cone. At any given level their contact radius is a perfect circle equal to the radius of the entire stylus. This radius is orders of magnitude larger than the radius of the edge on a cutting stylus, so a conical stylus will just slide right past fine modulations without reacting. Cartridges with conical styli will always have the worst HF response, other things being equal. They have progressively greater and more audible problems as they approach inner grooves, where the size of modulations for a given frequency is smaller than on outer grooves. Inner groove distortion will tend to be worse with a conical stylus than with other shapes that can read small modulations more accurately.
ELLIPTICAL
These are more egg-shaped when viewed in cross section. An ellipse has multiple radii, and the two small radii define the sides that contact the groove walls. This means they read HF modulations better and distort on inner grooves less, compared to a conical type. Since the stylus's cross section is no longer a "dumb" circle, stylus rake angle (SRA) starts to become a factor. Conical styli are fairly insensitive to SRA, elliptical styli are more so.
LINE CONTACT
These have long, fairly sharp contact edges. They can "see" and trace much smaller modulations than an elliptical stylus. The length and fineness of the contact lines makes azimuth adjustment and SRA extremely critical. Choosing a line contact stylus but ignoring these adjustments would largely waste the cartridge's potential.
MICRO-RIDGE
This is the most complex shape among today's styli. Imagine an ellipse (more or less) but with a very thin ridge sticking straight out from each end. Each ridge has a very small radius edge. This profile sees the finest modulations of all AFAIK. This means azimuth and SRA are still very critical. Micro-ridge styli are best at tracing small modulations, so they have the least problems on tight inner grooves. I have a few inner groove torture test LP's that no conical or elliptical stylus that I've tried can play cleanly. It takes a top quality cartridge with a micro-ridge stylus to make those grooves sound like music instead of a fingernails on a blackboard.
Obviously the rest of the cartridge will also impact the sound, but in general conical styli (lower level Grado's for instance) have great mids, rolled off highs and frequent inner groove problems. Elliptical styli occupy the middle ground. Micro-ridge and line contact styli offer the potential for superior frequency response and lower distortion on challenging passages, but also require more care in setup.
I'm not sure why a micro-ridge stylus should ride quieter in the groove than other shapes, but I agree with Sbank. The ZYX's I've tried (six different models) were uniformly excellent in this respect, and better than most other cartridges I've heard. Paradoxically, they also require the records to be cleanest to perform their best. The tiniest fleck of dust will impair micro-dynamics, imaging and soundstaging without necessarily raising the noise level.
I haven't heard a JMW. I have heard Shelters on a Graham 2.2, Basis Vector and other non-unipivot arms, as most of you know (too well!). Micro-dynamics and imaging were better on the (stabilized) Vector than on the (less stabilized) Graham, and arms with more stable bearings did better still. That was the origin of my comment about unstabilized unipivots vs. other designs. This was only one system and five or six arms, so I may be all wet in my conclusions. That's just what I heard.
