Unipivot tonearms less forgiving of Vinyl quality?


Couple of times that I have come across unipivot tonearms (once in my own system), I observed that when the vinyl is really good (physical quality and recording quality) the sound was superb, really special in terms of dynamics but when a slightly worn out/old vinyl is played the sound was equally coarse. Typically old vinyls which have been played a lot many times (generally pop/rock recordings) can have more noise but through unipivot tonearms it seemed to be exaggerated, the music sounded relatively abrasive (something like poorly implemented oversampling dacs).

Is it something to do with unipivots ? Or is it a case of tonearm not setup correctly ? I know the TT and cart also plays a major role in this but I did hear those setups with regular gimballed arms and they seemed to be lot more accommodating of such vinyls, playing more music than noise.

Has anyone else noticed this ?
pani

Showing 1 response by dougdeacon

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.