Unipivot tonearms less forgiving of Vinyl quality?
Recently, I mentioned some math that Mark Kelly did concerning unipivot tonearms. My take from all that is that a unipivot can be less forgiving, if it is designed carelessly. The reason is because of physics that apply specifically to unipivots and no others. The link... http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=473487 |
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A little bit of engineering: The azimuth of the cartridge can have a big effect on its sound- imagine one side having a different amount of contact than the other groove wall, and at a different elevation. You may indeed encounter excess noise if the azimuth is not correct. Now examine the physics of the unipivot. Some designs can oscillate above the exact center and apogee of the groove. If you can see the angle of the arm that is a lot in terms of what is happening with the stylus. The Graham uses a magnet system to stabilize the tendency/ability to oscillate; what you can take from this is that the effective mass of the arm cartridge setup is critical to reducing this oscillation as the cartridge tracks, plays bass and negotiates warp. The Graham, due to its stabilization, would seem to be less critical of this effective mass/ mechanical resonance issue. So if you encounter this problem with a unipivot the first thing I would look at is the effective mass and how that interacts with the compliance of the stylus. There are other variables that must be attended if you are to have success- for example loading, which is far more critical if you have a preamp that is unstable with RF energy and a LOMC cartridge. On this account, I would be hesitant to ascribe too much to the unipivot itself until you have some of these other variables nailed down. |
Agree with Tobes. Because their contact radii are smaller, line contact and micro-ridge styli can trace groove modulations having shorter wavelengths than other stylus shapes. Conical/spherical styli are at the opposite end of the spectrum, with ellipticals falling somewhere in between. If a stylus can't trace a particular groove modulation cleanly (because its radius is longer than than the radius of the modulation) then the sound of that modulation will be distorted. This is true whether the the modulation was cut by the mastering engineer as part of the music or caused by user abuse during previous plays. The radius of many scratches and other types of damage is far shorter than that of any music. A short radius stylus will track over it cleanly and reproduce it with less "ringing". You'll hear the snap or crack or thump but it will be crisp, clean and will have little or no overhang. By contrast, a "fat" stylus will be displaced longer in time as the transient slides past it, making the sound longer, more slurred and more noticeable. I doubt that unipivot vs. fixed bearing in and of itself has much impact in this area. This isn't to say that the arm isn't involved. It very much is. But the mechanisms by which an arm is "noisy" or "quiet" involve more than just which type of bearing it uses. As noted, many groove damage events produce transients that are more sudden and have greater amplitudes than any music cut on any record. Imagine, if you will, the stylus running into and jumping over a little wall. No cartridge can convert 100% of the resulting violent cantilever movements into electrical signal. Inevitably, some of those movements will leak into the cartridge body as mechanical energies. It then becomes the job of the cartridge body, headshell and tonearm to dissipate that energy and NOT allow it to reflect back into the armature, since that will produce a spurious "echo" of the original event. Such echoes prolong the sonic event past the actual movement of the cantilever, which makes surface imperfections more noticeable than they would be in a better system. How well a tonearm dissipates these leaked energies depends on more than its bearing type. I've heard noisy and quiet arms of both kinds. Unless everything else about the two arms were equal, it would be an over-simplification to draw a general conclusion that one bearing type will be quieter than the other. |
