Cartridge question

viridian

chart below indicates what is normally understood: elliptical has MORE contact area than Spherical

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I have to believe Johnathan Carr made a typo in the comments you cited

• Posted by jcarr (M) on January 7, 2005 at 17:41:40

  In Reply to: Re: The virtues of a spherical stylus posted by Tetrack on January 7, 2005 at 08:13:53:

   

"I have some stylus articles that Namiki published when they introduced the Microridge (also known as microline among other names) profile, so let's look at the manufacturer's figures.

A 0.7mil spherical stylus (18um radius where the stylus contacts the groove) has a contact area of 30.5um(sq.) - one wall.

A 0.5mil spherical stylus (13um radius where the stylus contacts the groove) has a contact area of 23.4um(sq.) - one wall.

A 0.3x0.7mil elliptical stylus (18umx6um radii where the stylus contacts the groove) has a contact area of 20.6um(sq.) - one wall."

**** chart above shows .3 x .7 = 40um****

which fits common understanding

"A line-contact stylus (45umx6um radii where the stylus contacts the groove) has a contact area of 46.7um(sq.) - one wall.

A microridge stylus (75umx2.5um radii where the stylus contacts the groove) has a contact area of 62.1um(sq.) - one wall."

hth, jonathan carr

@elliottbnewcombjr 

buy an advanced stylus shape: Line Contact/Microridge/Shibata/SAS: they cost more, but last much longer

All these advanced profiles have far smaller contact areas with the disc.  So the friction is concentrated over a smaller area and the pressure per unit area will be greater, thus wearing the stylus (and disc) faster.  Furthermore, advanced profiles deliver their performance improvements because the contact area is small and the disc is thus 'read' more faithfully.  The fine line contact soon enlarges with wear and some of the performance edge is lost.

It is important to remember that something can rarely be had for nothing.

clearthinker

you have it absolutely backwards, is this a joke?

look at row B in the chart

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The cutter makes the groove, making 100% groove contact

advanced stylus shapes get closer and closer to the cutter shape, each type on the chart making progressively more contact with the groove walls.

Line contact styli have a much larger contact area than conical or elliptical types because they fit more snugly in the groove and contact more of the groove from top to bottom.  Not only did J. Carr provide the numbers, the chart clearly shows this as well (line E of the chart, and the illustration on line D).

What is critical for line contact type cartridges to work properly is good alignment.  Azimuth is particularly important.  I have also found that vta/sra is also important (small changes can be heard).

AsFor wear, with proper care and clean records, I easily get at least 1500 hours on the cartridges I’ve owned.  Way back when I used elliptical cartridges, I got MUCH less hours of use (but it was cheap and easy to change styli).  Of course this might be attributable to other causes (like the quality of diamond used).

clearthinker

perhaps you are misled by ROW C showing front to back thickness.

Viewing the Groove from the front: no matter the amount of groove sidewall ’profile contact’, only a speck of the sides of any shape touches the groove wall.

Viewing down: Quad, modulations up to 50,000 hz are very ’short’ (thin) front to back, thus the new stylus shapes had to be thin front to back to fit/follow those thin modulations.

Manufacturing techniques to match both the side profile and maintain ’thin’ front to back had to be developed, even today not many can do it!

Stylus 'wear', is when the sides of the stylus get flat (thick), unable to follow modulations as well, and causing progressively more damage to the grooves