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Efforts to compensate for tracing distortion (caused by the difference in shape between cutting and playback styli) by creating an inverted signal to correct the playback distortion and adding it to the cutting signal were undertaken by companies such as RCA, Telefunken, Nippon Columbia and Toshiba EMI during the period between the mid-1960s and early 1970s, Some examples of this effect are shown in Fig. 5.56 to 5.59.

The effects shown above were obtained by calculating the playback distortion for a spherical stylus, creating a inverted compensation signal, cutting the disk, and reproducing the sound with a spherical stylus. That the correction is a great improvement is obvious. It is common knowledge that playback distortion is caused by the difference in shape between recording and playback styli, and that the improvement gained by using an elliptical stylus is highly variable, as illustrated in Fig. 5.60.
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The graph above clearly shows that playing the record with an elliptical stylus produced nearly as much distortion as a spherical stylus without compensation. The state of the industry was such that if all of the playback styli were spherical, then a great deal of the distortion could be compensated for; but when elliptical styli, which are narrower than spherical ones, began to be sold in the latter half if the 1960s, the audio maniacs jumped on them immediately. Thanks to this audio mania, the effect of playback distortion compensation was limited, and it failed to become popular in spite of all the trouble and effort that had gone into its development.

Nevertheless, this research into distortion compensation and stylus geometry has proven to be useful. In September 1970, JVC developed a discrete 4-channel record called the CD-4. As shown in Fig. 5.61, the sum of the front and rear signals were recorded in the normal left and right channels respectively, and the difference between the front and rear signals was recorded in the left and right channels on a frequency modulated 40 kHz carrier signal.

As CD-4s required low playback distortion at high frequencies, and as narrow styli such as the Shibata stylus were being developed and introduced, distortion compensation for these narrow styli was also implemented. Unfortunately, even though the CD-4 brought together all of the latest technologies, it was short-lived due to a lack of demand for content.

Regarding 4-channel records, it is interesting to note that (with the exception of surround sound for movies on DVD, etc.) there is the same lack of demand for content even now (when multi-channel digital audio is easy to implement and its adoption should be expected) as there was when Miura et al. conducted the evaluation experiments described in Section 5.1.3.
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Figure 5.62 provides a rough outline of the process of manufacturing a master disk, from lacquer disk to stamper.

The evolution of this process and the materials used will be explained below.

Master disks were made by the methods described in the following paragraphs. Montan wax, beeswax, and vegetable wax were melted together in a suitable ratio (einem spezeillen Verhältnis) and poured into a mold to make a wax disk.

The cooled wax disk was smoothed on a lathe (Drehteller) to a thickness of 30mm (3cm dicke Wachsscheibe)and was used for recording, Wax disks lacked electrical conductivity and needed to be treated, so methods such as brushing on graphite or embedding a copper wire in the periphery of the disk were used to give the disk conductivity before electroplating.

However, the size of the graphite crystals or damage caused by the brush during application could cause surface noise problems because the smoothness of the record face could not be guaranteed.

The graphite process to add conductivity was replaced by a gold sputtering process developed by Bell Laboratories in the late 1930s.

This method was not perfect either: the wax disks, lacking homogeneity, would degas (ausgasen) in the vacuum, causing the gold vapor to be deposited unevenly.

Another problem was the excessive temperatures at the disk face during vapor deposition, which would reach 80°C to 100°C. Such were the conditions when lacquer disks appeared.
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However, as with wax disks, when it came to depositing a gold layer on them, the problem of plasticizers and residual solvents evaporating from the master due to the heat of vacuum sputtering (Beschichtung) remained unsolved, and silver and copper sputtering did not offer any improvement.

Furthermore, sputtering equipment was apparently expensive at the time. One might suppose that this state of affairs prevented sputtering from becoming popular, and led to the transition to silvering.

Although silvering was already being used to coat glass mirrors long before it was used to make master disks conductive, it wasn’t until around 1950 that it began to be applied to lacquer disks. Table 5.11 shows an example of a silvering solution and a reducing solution used for silvering lacquer disks.

Table 5.11 An example of a "silvering solution" and a "reducing solution" used for silvering lacquer disks to provide conductivity.
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The 1950s saw the introduction of spraying methods, and the process gradually came to be automated.

An example of an actual process would be as follows: A lacquer disk would be mounted on a turntable and rotated, and then it would be rinsed (abgespült), washed with a cleaning fluid, rinsed (abgespült), sensitized with stannous chloride, rinsed (abgespült), sprayed with silver solution, and rinsed (abgespült) again. These processes were on timers, with many records being processed in parallel automatically.
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Electrotyping is used to precisely reproduce the microscopic grooves found on lacquers. Fundamentally similar to electroplating, this method enables an exact duplicate of a matrix to be produced by electrically depositing metal (nickel) onto the matrix until it reaches the required thickness, after which it is detached.

This requires the creation of an atomically-thin metal oxide layer on the surface to serve as a release liner to allow the deposited metal to be detached, a process using anodizing which is referred to as “passivation.”

Electrotyping allows things that are impossible to machine or difficult to process to be duplicated with great precision, Sub-micron tolerances are said to be possible.

First, the master disk is electroplated with nickel using a Watts bath. A typical example of the solution used in a Watts bath is shown in Table 5.12.
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Electroplating is carried out at a current density of 10–25 A/dm2 for approximately 1 hour to produce a layer 0.05 mm thickness.

After nickel plating, copper electrotyping is performed. Copper electrotype has a long history, having been used for electrotype printing plates, etc., since the 19th century.

Copper electrotypes have less internal stress than electrotypes made using other metals, and are quite appropriate. However, copper stampers (Press-Matrizen) required enough strength and flexibility to withstand the stress of pressing records in LP manufacturing. Attempts were made at nickel electrotyping, but the great internal stresses hindered progress.

Then, shortly before the outbreak of World War II, an electrotyping process using nickel sulfamate that produced very little internal stress was developed in the United States. Table 5.13 gives an example of the composition of a nickel sulfamate bath.

Under these conditions, approximately 0.2 mm of nickel would be deposited over the course of one to two hours, and after chrome plating, the back of the disk would be sanded and the disk finished to facilitate pressing.

By the end of the 1950s, electrotyping was being used to make not only stampers, but mothers as well. Nickel masters and nickel mothers became widespread, and are still used to this day.

Today, analog record manufacturing has dwindled (rückläufig), continuing only as small-scale production in a few countries, having been replaced by CD and DVD manufacturing.

The manufacturing process for CDs, LaserDiscs and DVDs is similar to that for analog records, and the same technology is used. Without electrotyping technology, the mass production of LaserDiscs, CDs and DVDs, would be impossible.

Master disk and stamper manufacture involves many aspects of electrotyping technology, such as rendering the matrix conductive, separating the electrotype from the matrix, uniform deposition, managing stresses in the electrotype caused by plating conditions, such as current density, and considering the physical and mechanical properties of the metal used (nickel), each of which demands a high level of technology.
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(78er) SP records were manufactured from 1910 until 1959. Until 1928, single-sided (solid) records were manufactured, and from 1929 until 1959, double-sided laminated records made from surface and core materials with superior sound quality, wear resistance, and noise levels were manufactured. Both types had an overflow attached to the edge of the record, which would be trimmed off with a cutter.

In Japan, manufacturing of LPs (Anmerkung : 30cm Mono) was commenced in 1951, and EP (Anmerkung : 17cm Mono Singles) manufacturing began in 1954.

It was in 1951 that Nippon Columbia released the first Japanese vinyl LP record: Beethoven’s Symphony No. 9 in D minor, op. 125 “Choral” conducted by Bruno Walter with the New York Philharmonic Orchestra.

This record (shown in Fig. 5.63) is registered as one of the Essential Historical Materials for Science and Technology by the National Museum of Nature and Science as the “First Japanese-made vinyl LP record” (No. 00097).

EP records were designed with autochangers in mind and were called “donut disks” because of the large hole in the center.

The first Japanese EP record was released in 1954 by JVC, and featured “Blue Canary” sung by Dinah Shore.

LP and EP records were made from different materials from 78er SP (Shellack) records (now being made from a vinyl resin base) and solved many of the drawbacks of SP records, having low surface noise, excellent durability, light weight, toughness, high fidelity characteristics, and coming in many colors.

At first, Japanese records were pressed from imported biscuit-shaped material from the United States, but efforts were made to domesticate vinyl chloride resin production and this finally became possible in 1956.

Disk records go through many stages such as pressing, preheating, extrusion, pressing, packaging, previewing and inspection, which includes passing through an automatic noise detection unit. In 1965, some EP records were made using injection molding. (vermutlich wie beim Kunststoff-Spritzen).
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Wax disks were used for recording SP records until around 1951, after which they were replaced by acetate disks.

Shellac remained the dominant record material for over fifty years after Emile Berliner first thought of using it, only being superseded when the LP record was invented in 1948.

Shellac is a natural resin secreted by the lac insect (a kind of scale insect) that is produced in places such as India and Thailand. Shellac was mixed with natural resins such as rosin and copal, fillers such as clay and baryte, and carbon black, and was kneaded using a heating roller.

• Anmerkung : Ganz viel über Schellack steht auf den Schellack-Seiten.

Early solid SP records mainly used shellac. Later laminated records also used shellac as the main surface material.

Double-sided lacquer disks (aluminum disks coated with nitrocellulose lacquer; sometimes called “acetates”) were used to record LPs and EPs. These disks were supplied by the US companies Transco and Capitol Audio Disk for many years.

• Anmerkung : Mehr über Audio Disc von AUDIO DEVICES steht hier bei den US-Zeitschriften.

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Regarding LP and EP disk materials, Union Carbide Plastics Co. researched materials for records for over 20 years beginning in 1930, and perfected a vinyl chloride/vinyl acetate copolymer for LP and EP records. This material was developed with the aim of using it in the same presses used for pressing 78-rpm shellac records.

This copolymer displayed better workability than other plastics during pressing, and other advantages included a shorter pressing time, excellent mechanical strength and abrasion resistance, minimal loss of high frequencies, and excellent acoustic characteristics.

Generally, adding plasticizers to vinyl records proportionally increases their susceptibility to temperature, groove wear, and sound quality deterioration at high frequencies.

The PVC must therefore not use plasticizers, but still have good plasticity. Records are made with a rigid PVC resin, and a copolymer with a relatively low degree of polymerization and a high copolymerization ratio is used.

A rigid PVC composition contains stabilizers, fillers, lubricants and colorants; these are mixed uniformly in the kneading process and compacted to make vinyl records.

One kind of vinyl resin for records that was well known around the world was Vinylite VYHH-3, a copolymer resin made by the Bakelite Company that contained 87% vinyl chloride and 13% vinyl acetate. This resin used to be imported into Japan.

Japan began to develop rigid vinyl for records around 1950, with Zeon Corporation, Shin-Etsu Chemical Co., Ltd., Kaneka Corporation and others beginning to supply vinyl from around 1956.

An example of the composition of the Bakelite Company’s VYHH-3 is shown in Table 5.14, and the composition of Zeon Corporation’s 400X150P is shown in Table 5.15.

The process of making records with a stamper and the materials described above is known as molding (in eine Form pressen). Methods of pressing can be generally classified into pressing and injection molding (Spritz-Pressen). 12" and 10" records are usually made with the first process, and CDs and 17-cm records with the second.

It is widely known that molding conditions have a great effect on manufacturing efficiency, characteristics, and sound quality.

Record companies work to find the optimal conditions and treat this information as a trade secret, so there is not much information available on this subject.

• Anmerkung : Bei der CD Herstellung gab es zwei unterschiedliche Patente zur industriellen Großserien-Herstellung von CDs, über die auf den CD-Seiten ausführlich berichtet wird.

During the pressing process, the nickel and chrome stampers are mounted on the press, preheating is applied, the labels and materials are added, and heat and pressure are applied to ensure the materials spread evenly. Then, the record is cooled to finish the process.
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Manufacturing efficiency would be increased if the preheating, heating, pressure, and cooling stages were shortened, but this may increase the number of disks where the grooves are not faithfully reproduced, or
where noise is increased. The pressing characteristics of the material also change if composition is changed. Table 5.16 lists conditions that can affect the pressing cycle.
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• (1)|Record size
• (2)|Fluidity of materials
• (3)|Stamper groove shape
• (4)|Mold structure/thermal conductivity
• (5)|Molding equipment structure
• (6)|Molding conditions
• (6)-1|Materials
• (6)-2|Temperature
• (6)-3|Steam pressure
• (6)-4|Cooling water temperature/pressure
• (6)-5|Press pressure

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