Shure Bulletin (written in 1954)

1954: before stereo, now these forces are even more important

I feel lucky to just find this:

Shure Bulletin, Original 1954; Last Edit Date 7/18/2022

excerpts (for those who don’t RTFM).

A 33 1/3 RPM record has about 225 grooves per inch, each groove approximately one-half the width of a human hair. The groove on a 12 inch, 33 1/3 RPM record, if uncoiled, would be over one-half mile in length.

The shape and size of the impressions engraved in the rotating disc are determined by the pitch and level of the signal being recorded. The higher the pitch, the greater the number of times per second the cutting stylus will vibrate from side to side. The level of the sound being recorded also affects the impressions engraved upon the disc. Increasing the recorded level causes the cutting stylus to engrave deeper impressions into the walls of the grooves. Conversely, a reduction in level causes a reduction in the distance the cutting stylus swings from left to right, causing it to engrave shallower impressions. These impressions, as mentioned earlier, are microscopic three dimensional duplicates of the sound wave pattern. (stereo, even more complicated, came after this bulletin was written in 1954).

stampers are changed after each 250 pressings, since even the microscopic wear created in pressing is not tolerated in precision record manufacture. This is how a record is manufactured and how the impressions are created on the walls of the grooves.

(again, mono grooves are being discussed): The stylus tip, when in good condition, touches the groove walls at only two points. The entire weight of the stylus and the structure which holds it is concentrated at these two microscopically small points. When this concentration of pressure upon the points of contact is calculated, we find it to be approximately 26 tons per square inch.

walls of the record grooves are, of course, subject to the same pressure, but only for the fraction of a second

stylus tip in the record groove follows a path in much the same manner as automobile tires would follow the ruts in a country road.

This friction causes the gradual wearing away of the stylus material at these points, and creates what are called "flats". The amount and degree of wear are apparent when the tip is viewed from the side, using a microscope. It is these flats on the stylus tip which are the direct cause of increased record wear, distortion, and reduced tonal range. Although these flats appear on both sides of the stylus tip, the amount of wear is not the same on both sides because of the side thrust created by the tone arm mounting method. This can be off-set somewhat by proper setting of the anti-skate force.

Depending on the wear, the stylus tip can become a cutting tool, and if continued in use, it will eventually take the shape of a miniature chisel.

wearing process is also hastened by the abrasive action of dust in the grooves. The wear on both the stylus and the record groove can be considerable.

the downward pressure of the stylus tip on the record groove. The greater this pressure the greater the amount of friction generated between the walls of the record groove and the stylus tip. Increased friction naturally results in increased wear.

check the stylus pressure once a month.

worn stylus tip will no longer fit into the engraved depressions since the flat on the stylus tip is wider than the opening of the depression. stylus tip obviously cannot follow with "extreme exactitude" the variations in the groove, the signal is nowhere near a perfect replica of the original recorded sound wave

the higher the quality of the reproducing equipment the wider its tonal range, and any distortion of the high pitched sounds is immediately apparent.

average record collection is usually worth more than the equipment on which it is used, and includes irreplaceable recordings. Preservation of the records should be the most important consideration.

Also of considerable importance is the ability of the pickup itself to follow the impressions engraved upon the groove walls with the least resistance to the motion they cause. This is called "trackability" and is related to a specification called "compliance."

Due to its great hardness, the diamond can be polished to a higher degree than any other substance. A higher polish results in a smoother finish, which greatly reduces friction.

An analysis of the "dust" removed from a number of stylus tips, which had been used on dirty records, showed that it consisted of approximately; 12% jagged silica particles, 35% diamond dust, 40% miscellaneous particles, including soot, grit and particles worn from the record groove itself. The remaining 13% consisted of fibers and lint. almost 65% of the extraneous material is harder than the comparatively soft record material

also increases the amount of friction. Increased friction results in increased wear on both record and stylus and also increases the amount of static electricity generated. Most plastics are insulators and retain a static charge. the friction generated by slipping the record into its jacket increases the static electricity.

Tests showed that both airborne dust and debris worn from the stylus tip itself are the greatest cause of excessive record and stylus wear. Complete removal of dust and grit from the record grooves resulted in increases of up to 60% in the useful life of both records and styli.

A record (cleaning) pad can actually damage records by scratching them and grinding microscopic particles of dust and grit into the grooves. the particles of dust and grit are often as large as the recorded impressions in the record groove. dust problem is further aggravated by the fact that the new vinylite records actually attract dust and retain it, due to their electrostatic properties.

The grooved section should never be touched, since the skin oils and grease from the hands is transferred to the record, causing any airborne dust to adhere to the spot or area touched.

any attempt to clean records is commendable and even a poor cleaning is better than none.

Completely removing dust and grit from a record is not a simple problem. A number of factors must be considered. Firstly, the cleaner must not contain any gummy substance that will remain in the engraved depressions in the record groove. Secondly, the cleaner must completely penetrate these same depressions and remove any dust or grit they may contain. Thirdly, the cleaner must not affect the record material itself in any manner. Record dust/dirt when examined under a microscope consists of grease, stylus particles, abrasive material, and solids which resemble wool fibers covered with a soft waxy substance.

consider the use of an anti-static agent as its repeated use will prevent the attraction of airborne dust or grit. record should be recoated as often as is necessary since the anti-static agent does not have a permanent effect.


Excellent article!

 Few years ago, I bought a pristine looking Robert Johnson Lp. Played it and it was super noisy. 
Took the LP to the operating room where we used powerful microscopes for brain surgery. All along the grooves of the entire LP were vertical cuts, deep  chisel marks on the side walls of the grooves. They looked like well ordered uniform cuts. 
 My impression is the cuts were caused by a broken stylus, that had a jagged edge and too much weight. 
 When I was a kid, I placed a nickel on the heasdshell so the “needle” stayed on the record. (Don’t tell my brother, they were his records). 
 Mea culpa. 

Putting a penny or nickel on the headshell was considered a tweak in those days, indicating you were in the presence of a real audiophile.

Shure later realized that their position of dominance in the US market gave them the standing to propound that “trackability” at minimum tracking force was the goal of high quality record playback. This notion was not universally accepted by peer companies like Decca and Denon, whose research showed no benefit from low VTF, but big damage from mistracking. Thus began the movement towards higher compliance cartridges, when compatible low mass tonearms were not commonly available, causing much trouble.  IMO this was done for marketing advantage to the detriment of consumers.