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While the Dolby B gained popularity as the de facto standard system, other competing systems were developed and put to use, as outlined below.

JVC developed its own four-channel stereo record, the “CD-4”. It also developed its own noise reduction system in the ANRS (Automatic Noise Reduction System) format as a means to reduce the noise of the difference signal recorded in the UHF range to produce a rear signal.

JVC cassette decks started being produced with an inbuilt ANRS system not long after the Dolby B appeared. Although ANRS was JVC’s own technology, it operated very similarly to the Dolby B system and the two were thought to be compatible.

Dolby carried out negotiations with JVC on the ANRS format in order to promote standardisation and ensure patent licencing fees, but in the end it accepted the originality of ANRS and formally acknowledged its compatibility with Dolby B. Many JVC ANRS cassette decks had NR switches labelled “ANRS/Dolby B”, indicating that there was compatibility between the two.

dbx is a noise reduction format developed and released by American company dbx, Inc. in the early 1970s. It started out as a high-performance noise reduction system for business machines to rival the Dolby A system.

Designed to work across a wide range of frequencies and levels, its compression/expansion worked in a logarithmically linear manner. Fig. 11.7 shows input and output using the dbx format.

Since any signals above 0dB are attenuated, it could compensate for any tape saturation and could produce drastic noise reduction, meaning it was superior in many ways.

However, it was very diffcult to incorporate the system into any popular-model tape recorders, as the circuit was complex and costly and uniform compression/expansion was carried out regardless of signal level or frequency, meaning it would be susceptible to breathing (athmen oder pumpen) in machines with poor basic performance.

An increasing number of manufacturers began to use it in high-end cassette decks due to the good sound quality and drastic noise reduction effect; to some extent, it gained a reputation as offering higher-end NR than Dolby.

It gained relatively wide acceptance in the world of business machines and was often used by companies such as recording studios. While the introduction of music tapes presented no obstacle to the system, it was never put to use in consumer machines and gradually disappeared off the market.

The Dolby B, ANRS and dbx systems were incorporated into cassette decks relatively early on. While this contributed to the Hi-Fi capabilities of the Compact Cassette, as the adoption of digital audio became an increasing reality from the late 1970s onwards, the Compact Cassette had to further expand its dynamic range, in other words, increase its noise reduction effect.

Every Japanese manufacturer at the time developed and released its own noise reduction system, working on its own developments as well as joint developments with manufacturers in the West (Fig. 11.1).

Meanwhile, the veteran company Dolby announced the Dolby C, the successor model to the Dolby B. The Dolby C system ran two B-type operations in stages, expanding its noise reduction range to lower frequency areas, producing a noise reduction effect of 20dB or more.

Comprising two B-type circuits together, as shown in the block diagram in Fig. 11.8, the C system could also operate as a B-type system by running only one phase on one circuit. Not only was it easy to switch between B and C operation, there were also obvious cost benefits to combining it all in an integrated circuit.

While it offered less in terms of noise reduction and tone sensitivity compared to other formats, it performed at an adequate level to be used as a Compact Cassette noise reduction system in the digital audio era.

Given the degree of familiarity with the “Dolby” name, many manufacturers deemed it benefcial to adopt the Dolby C system; thus, the Dolby C secured its place as the de facto standard system.

When CDs appeared in 1982, the audio world immediately became digitised and the Compact Cassette sound quality competition came to a standstill, although the Dolby C kept its popularity in the feld of high-end machines.

This competition between NR systems prompted the development of secondary functions in cassette decks to make NR systems work more accurately, thereby playing another role in improving the performance of cassette decks.

Compact Cassette noise reductions systems all worked on the basis of compressing and expanding analogue signals. The operating principle was that tape recorders had uniform recording and playback properties, that is, the signal level during recording and playback was identical and that the frequency response was even.

When this assumption was disproved, there was a fear that the difference in levels would increase through compression/expansion. Any disparity in frequency response potentially meant that the NR could malfunction.

While there was a certain degree of tolerance in the precision and stability of Compact Cassette machines, if different tapes were to be used, there would be subtle differences in sensitivity and frequency response, depending on the tape.

To prevent this variability, the drawback of noise reduction, and to ensure high sound quality through precise operation, high end machines appeared equipped with a “calibration function” for each tape.

These machines had a standard signal generator inside them and could provide level adjustment for recording and playing back each tape; the frequency response could also be adjusted according to the amount of bias. Some of these sets were operated manually, while some sets were developed that used a CPU to make these adjustments automatically.

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The early Compact Cassette tape recorders were released with single-motor mechanisms, aimed at maximising functional performance, downsizing and simplifying (Figs. 12.1, 12.2).

Since the overall machines could be made smaller than the open-reel systems and could get by with the minimum necessary power to drive the tape, developers used low-output DC motors in them.

However, the high-performance cassette deck followed on the tail of these machines and grew in popularity. To have the performance and function of serious audio equipment, these tape recorders had to meet higher standards than the small-scale machines in terms of the accuracy and reliability of the machine itself.

While they still had the same tape recorder mechanisms to play Compact Cassettes, these new machines were the successor models. The early deck-type machines were intended for use in the home; many of them had the AC motors that were in standard use in the open-reel machines.

When the Compact Cassette appeared, DC motors were used in toys and trivial consumer electronic goods; they had hardly ever been used in audio equipment. By contrast, there were already a number of superior AC motors designed for audio systems, having been used in record players and open-reel tape recorders.

It was also very important for record players and tape recorders to maintain an accurate rotation speed, so hysteresis synchronous motors, which could rotate in sync with the power frequency, were well suited to audio equipment.

Rapid improvements were made to the overall design of both the deck-type and portable-type machines. The main driving mechanism in both types changed from an AC motor to a DC motor, due to the development of servo motor technology to maintain a steady rotation speed and successive developments on DC motors designed to suit audio equipment.

This resulted in greater reciprocal interaction: the mechanism design required the motor to be high-spec, as it was the core device; in turn, the transport mechanism had to be more advanced to handle the new motor.

The Compact Cassette size restrictions would have been another factor, as this would have naturally played a part in determining the size of the mechanism and prompted the use of small-scale DC motors. Among other factors, suitable motors for audio equipment had to run smoothly and silently with no rotational irregularities; they had to guarantee a long operating life of at least 1000 hours under a certain load; they had to produce minimal electromagnetic noise and readily produce a prescribed rotation speed.
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Many of the DC motors used in the early Compact Cassette machines had mechanical governors as a means to attain fixed speeds. A mechanical governor is a switch that uses centripetal force (also ein sogenannter "Fliehkraftregler") generated in proportion to rotation speed to automatically turn the power supply to the motor on or off (Fig. 12.3).

The counterweighted governor is directly connected to the motor’s rotational axis; as the rotation speed increases, the centripetal force makes the counterweights move along the outer circumference, thereby braking a connection.

The current stops and the rotation speed decreases. If the rotation speed drops below a certain limit, the centripetal force decreases and the connection is made; the current resumes once more.

Repeated tens to hundreds of times per minute, this operation serves to maintain a fxed rotation speed. Although it is a relatively simple, low-cost mechanism, it is prone (anfällig) to generating electrical noise (meist Funken) as the connection joins and breaks.

Furthermore, if constant speed is a strict requirement, it becomes very complicated to regulate contact pressure and other factors, which affects the reliability and longevity of the device.

While only average in performance, such motors were often used in popular-model tape recorders because they were simple and cheap.

The governor motor had limitations to the constancy of speed it could produce; it also generated electrical noise and was somewhat unreliable. In light of these factors, efforts were made to introduce servo technology, as this was capable of producing a higher-performance motor.

Servo motors work by detecting rotation speed with an electronic sensor and then using that information to perform feedback control on the driving current.

A frequency generator (FG) was developed "to be used as a sensor" ???, working on the same principle as an AC generator. The FG principle comprises a multiple-pole ring magnet being rotated to induce an alternating current of a frequency corresponding to the rotation speed in a coil wound around a comb-shaped sensor. If the number of N poles is designated as N and the rotation speed as X rps, the current generated corresponds to N x X Hz. Figs. 12.4 and 12.5 show the structure and principle of FG. Fig. 12.6 shows the internal workings of an actual motor with a FG incorporated.

The size and frequency of the voltage generated are in proportion to the rotation speed and either can be used as a control signal.

By increasing the number of magnetic poles, it is possible to increase the accuracy of the sensor and gain a high-frequency signal even with a low rotation speed. However, if there are an excessive number of magnetic poles, the output decreases and the S/N ratio gets worse, thus reducing the reliability of the sensor.

Consequently, an appropriate FG with an appropriate output suited to the rotation speed used should be incorporated into motor design and assembly.

The FG output signal varies as shown in Fig. 12.7 (1) as the rotation speed varies. It takes the form of a combination of AM modulation, in which the amplitude changes in proportion to the rotation speed, and FM modulation, in which the frequency changes in proportion to the rotation speed.

The AM control signal method was often used in devices where cost was a major factor, as it could be achieved with a relatively simple electronic circuit, but it was not capable of demonstrating the full capabilities of the highly-anticipated FG.

By contrast, the method shown in Fig. 12.7 used to achieve a control signal through FM was called frequency control. It was often used in high-end machines such as tape decks as, although costly, it was fully capable of high servo performance.

Cassette deck mechanisms started out as basic, single-motor devices and developed into two-motor devices with independent motors for driving the reels, as shown in Fig. 12.8. This format enabled the dedicated use of the capstan-driven motor, which was key to precise tape feeding, making it possible to achieve high performance. A “direct drive” type was also developed, which had the capstan directly connected to the motor axis.

The direct drive system, with the capstan directly connected to the motor axis, was suited to audio equipment, as it could produce a low rotation speed with minimal vibration or operating noise.

It was also simpler and more reliable than other indirectly-driven systems, which used a power transmission mechanism such as a belt or idler as a reduction drive for the capstan. However, indirectly-driven systems allowed the rotation speed to be set at a more efficient rate and made it easier to maintain driving torque through deceleration.

They were likely to be used in small, inexpensive motors, giving a greater freedom of choice in motor selection. On the other hand, since intermediary components were used in power transmission, the overall structure of servo driving systems was more complex, making it a little more diffcult to operate the control system to its full capacity.

Direct drive systems were quite the opposite: they were mechanically simple and readily allowed accurate servo control. A large-diameter flywheel could not be used where there was a low rotation speed, or in a Compact Cassette tape recorder, so moments of inertia were not a reliable option.

It was therefore necessary to design the motor making the output frequency of the FG that detects the capstan rotation speed as high as possible, widening the servo bandwidth and making the rotation as smooth as possible. This required a brushless motor, which, although it was not cost-effective, was designed for use in high-end tape recorders.

Open-reel machines had quite spacious mechanisms, with a greater degree of freedom in terms of the drive system design and choice of motor; hardly any of them used a direct drive system. Direct drive motors were probably first developed for use in record players.

Matsushita developed a low-speed brushless motor for record players quite early on; this “direct drive” technology was then able to be used in the smaller cassette decks at an early stage as well. In 1970, the RS-272U (Fig. 12.9) became the world’s frst cassette deck with an inbuilt direct drive system.

While record players already held the dominant position as the main audio playback machines, a furry of new technology and product developments after the Second World War for all components accompanied major breakthroughs such as LP records and stereo-capable machines, making the record player the most important item of home audio equipment.

For instance, while manufacturers in the West had always supplied the best pickup cartridges, arguably the most essential component for playback, many cartridge manufacturers appeared in Japan from around 1960 and began to produce cartridges that were just as good as their counterparts made in the West.

In particular, Denon, which had played an active role in the disc-style recorder industry before the war, worked with the "NHK Science & Technology Research Laboratories" to produce the DL-103. Although they developed this cartridge in 1964 as a business-use device for use in FM stereo broadcasting, it brought in a lot of interest from audiophiles who were impressed by the high sound quality of the FM stereo broadcasts.

The MC cartridge was released in 1970 for consumer use and became well-loved throughout the world as a high-performance device.

Incidentally, it is still being sold to this day (wir haben 2012). As well as developments to the components in the transducer unit, such as the cartridge and the tonearm, developments were also taking place on the turntable drive mechanism, with remarkable improvements being made in performance, such as progressing from the idler drive to the belt drive and introducing servo technology.

Matsushita developed a low-speed brushless DC motor quite early on to be used in record players, announcing its brushless DC direct drive phono motor technology in 1969. While Sony also developed a direct drive phono motor around the same time, this was an AC motor. Although Matsushita was the first to announce direct drive technology, Sony released the TTS-4000 (Fig. 12.12) and the PSE-4000 record player system incorporating it in 1970, about one month earlier than Matsushita released the SP-10 (Figs. 12.10, 12.11).

The world’s first direct drive phono motors appeared one after another in Japan. For the first time, original Japanese technology was appearing on the world audio market.

Armed with the DC direct drive motor, Matsushita was able to take the top share of the world record player market. It was also able to apply the same low-speed DC servo motor technology to make a direct drive system for the tape recorder, thereby creating the world’s first direct drive cassette deck. It also applied the technology to a single-capstan, closed-loop, open-reel machine, releasing the high-end, high-performance RS-1500U (Fig. 12.13) in 1976. Fig. 12.14 shows internal and external views of the direct drive motor used in the RS-1500U.

As AC motors used induced currents and eddy currents, induced in a rotor by a magnetic field, they had greater torque uniformity. While this was good for sound, it meant they lacked controllability.

By contrast, DC motors were more controllable, but they had greater fluctuations in torque (Drehmoment) caused by the timing with which the magnetic poles turned to keep the motor rotating.

To prevent this required increasing the number of magnetic poles, thereby evening out the torque generated by multiple poles. Accordingly, although the DC motor presented more manufacturing issues than the AC motor due to greater complexity in the field winding structure, it was easier to increase its effciency.

As the DC motor control circuit did not have to deal with large AC currents, it was very compatible with transistor circuits. It lent itself to being made smaller and lighter, making it a good candidate for small-scale devices.

In fact, DC motors started being used in most of the audio-visual equipment that was brought out after this. In 1970, Sony released the world’s first direct drive phono motor using AC to ensure rotational torque stability.

While this was used in basic player systems for a time, the DC motor steadily became the standard. With the move to DC, studies began on how to suppress the fluctuation in torque occurring with polarity changes in the magnetic field.

A driving method was developed that generated torque in a theoretically linear manner rather than increasing the number of magnetic poles.

Generally, the torque generated by a DC motor corresponds to the product of the magnetic flux density (in the gap) between the rotor and the stator and the current fowing through the coil interacting with the magnetic flux in the gap.

Where the rotor is a thin, cylindrical magnet with multiple poles magnetised in a sine wave in the radial direction, the stator coils are positioned so that the two sets of poles have a phase difference of 45º.

A "Hall effect" sensor is used as a flux detector to ensure that the current flowing through the two coils corresponds to the magnetic flux of the rotor. When the current is linearly altered rather than switched, the torque generated by the first coil-magnet pair corresponds to the turning angle of the rotor.

This type of motor is called the BSL (Brush & Slotless) motor; it was developed to be the main motor used in mid- to high-end audio equipment. First used as a direct drive phono motor for record players, its scope of use soon expanded to cassette deck standard motors (Fig. 12.16) and direct drive capstan motors. An OTM (one
sensor two phase) type was also developed, which combined this with a pole detection sensor; this arrangement was used to slim down the Walkman.

Small-scale tape recorders made good use of the size of the Compact Cassette, developing into far more fascinating products than had been seen in the open-reel era.

This new type of small-scale tape recorder focused on being small, lightweight and easy to use rather than being Hi-Fi capable. They were also mostly battery-operated, so electricity consumption was a major factor for consideration.

Reducing the electricity consumption of the motor was a very significant issue. To start with, standard iron-core brushed DC motors were used in small-scale tape recorders. Motors were selected on the basis of being as small and as simple as possible, with mechanical governors for speed control and back EMF control.

However, the standard iron-core motors were limited in terms of their size and electricity consumption. It was deemed necessary to increase the performance of the set with each enhancement in functionality. Small-diameter, coreless motors were developed around this time and began to be used in handheld tape recorders.

The overall performance of the motor rapidly improved, not only in terms of electricity consumption, but also in terms of less mechanical and electrical noise and greater reliability. This greatly boosted the product value of the small-scale tape recorder.

While the rotor in an ordinary small-scale DC motor consists of a coil wrapped around a core, the rotor in a coreless motor consists of a cylindrical, “cage-like” coil; this is also called a moving coil (MC). As no eddy-current loss (core loss) occurs when the rotor turns, it is theoretically more effcient.

Other changes were incorporated into the design to make it more effcient overall, such as using rare-earth magnets to generate torque even with small diameters, or narrowing the space in which the rotor turns to increase the magnetic flux density.

These were also produced with inbuilt FGs and also used in servo control (Fig. 12.17). For more information on small-scale, handheld devices using small-scale coreless motors, see the discussion in Chapter 6 on product developments related to the Walkman.

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Thus far, listening to music on audio equipment had been a pleasure to be enjoyed at home. Ever since Edison and Berliner invented the phonograph and gramophone, music had been listened to in the living room, recorded on the medium of records.

Of course, venues such as restaurants and bars also used music products to entertain their guests, providing background music or music for dancing. Certain shops also specialised in providing certain styles of music for listening, such as jazz or classical.

In any case, whether it was played for the purpose of listening to “good music” or for creating a “pleasant environment”, it was always played indoors on large, bulky equipment.

Radio broadcasts began in the 1920s and rapidly gained popularity throughout the world, starting in the West and spreading to Japan.

Broadcasting was done through cutting-edge wireless technology; it was a ground-breaking means of transmitting information to the masses and people became enthralled by radio news broadcasts.

Radio broadcasts could also transmit music, something that was absolutely impossible through paper media such as newspapers, so it was not surprising that listeners readily welcomed musical broadcasts from the beginning.

While the gramophone and SP records (die 78er Platte) had already enjoyed some degree of popularity before radio broadcasts began, playing music had not really become a true form of mass entertainment, as one record could only play for ten minutes or less and gramophones and records were expensive.

When radio broadcasts began, the record industry was afraid that radio was encroaching on its domain; however, the outcome was the complete opposite: repeated radio programmes were very popular with listeners and prompted a major increase in gramophone and record sales.

Trend-setting radio broadcasts and records for playing music had a mutually beneficial effect on each other, creating a “home audio” culture. While pre-war radio broadcasts in Japan focused on providing information, such as news broadcasts, after the war there was a growing interest in musical broadcasts, inspired by the AFN (American Forces Network)* for American troops in Japan.

* AFN: Broadcasts for American troops, known as the FEN (Far East Network) in Japan until 1997.

Not long after the war, the AFN became a major presence in Japan, having given rise to a large number of music fans and audiophiles. At this time, the AFN was drawing on discstyle records recorded in the United States for its source of music.

Japanese audio engineers were profoundly inspired by listening to the tremendous radio sound quality afforded by American recording and broadcasting technology, the best in the world. Commercial broadcasting began in 1951 and further developments continued on music broadcasting in Japan.
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LP records (die 33er Mono LP) were released in Japan in 1951. These records were highly regarded by audiophiles not only for their longer playing time, but also for their high-quality sound.

High-quality music playback became popular immediately, resulting in a growing dissatisfaction with the quality of radio broadcasts. At the time, radio broadcasts were medium-wave AM broadcasts (bei uns Mitelwelle).

While various efforts were made to raise the quality, such as introducing stereo broadcasts using two AM stations, as television broadcasts gained in quality, AM radio music programmes ended up being mainly so-called “disc-jockey” programmes intended for car radio or portable radios.

High sound quality was delegated to FM broadcasts. By 1940, there were already around 30 FM radio stations operating in the United States.

FM (Mono-) broadcasting began to spread in earnest from 1955, when the F.C.C. (the United States "Federal Communications Commission") approved the transmission of news and background music using FM multiplex broadcasting sub-channels.

In Europe, West Germany planned to cover the entire country with FM, having had its medium-wave frequency allocation reduced (almost left - verloren) following its defeat in the war.

These broadcasts began in 1945 and soon their superior sound quality attracted the attention of countries such as the United Kingdom and France, thus spreading the popularity of FM broadcasting.

In 1957 and 1958, the NHK opened experimental stations in Tokyo and Osaka, while experimental commercial station FM Tokai started broadcasting in 1960. The Japanese had greater hopes for high-quality broadcasts than the noise-and interference-ridden broadcasts in the West; Japanese broadcasters set their sights on Hi-Fi music broadcasts from the start.

In 1956 (sorry, es war erst 1958), the 45/45 stereo LP record took hold in the industry, but stereo records were very highly priced for everyday users at the time.

Many audiophiles eagerly awaited FM stereo broadcasting. On 17 December 1963, the NHK made its first FM stereo broadcast. The first song was Mozart’s Symphony No. 40, performed by the Vienna Philharmonic Orchestra and conducted by Herbert von Karajan.

The preparations for FM broadcasting in earnest had thus been steadily laid. From 1969 to 1970, the NHK and commercial broadcasters began proper broadcasts, ushering in Japan’s FM age in earnest.

The commencement of proper FM broadcasting coincided almost perfectly with the appearance of Compact Cassette tape recorders.

These tape recorders received much attention as being capable of recording high-quality musical broadcasts. The NHK and many other interested parties had put a lot of effort into the sound quality of FM broadcasts, while Japanese audio manufacturers had competed ruthlessly (schonungslos) to develop the receivers.

As a result, FM broadcasts were a fairly high quality source of music. At the time, high-end, open-reel tape recorders were considered suitable for recording music and the use of a deck-style machine in conjunction with stereo equipment became a favourite among audiophiles.

Since FM stereo broadcasts have a 19kHZ stereo pilot signal and acoustic properties extending to approximately 15-16kHz, (in terms of specifcations) the open-reel machines had to perform in four-track stereo at 19cm/s.

Reverse machines were also well-received, capable of long, continuous recording of music broadcasts. Open-reel decks reached a height of function and performance in the early 1970s, when the so-called unattended recording function was added to record desired programmes from FM broadcasts.

By contrast, the Compact Cassette served as a memo recorder and was thought to be incapable of proper Hi-Fi music recording. However, its ease of use, potential for downsizing and firm position as the de facto standard were enough to show promise for the future.

Efforts were redoubled to produce technology capable of high quality sound and somehow rival that of the open-reel machines. Within a short time, the Compact Cassette had earned its own place as a serious piece of audio equipment. (See Chapters 8 to 12.)

Another factor contributing to the popularity of radio broadcasts was the personalisation of the audience. Listening to the radio or playing music on records was entertainment enjoyed in the living room together as a family. For a long time, it was normal to have one piece of audio equipment per household.

When "stereos" started becoming popular in Japan, most of them were bulky pieces of household furniture, whether they were ensemble devices or separate devices. However, Japan took the lead in downsizing this equipment using transistors, opening up a market for portable audio systems quite early on.

Once these portable radios became affordable in the 1960s, disc jockey programmes in the form of late-night broadcasting became immensely popular with the younger generation; programmes aimed at these young people introduced new musicians and the latest pop music from overseas, playing a major role in in the spread of music culture and the expansion of the record industry.

There was a growing interest in FM and FM stereo broadcasts from users accustomed to listening to music on small-scale radios seeking a better and more impressive sound.

While they preferred high-quality radios and stereos, the price of proper audio equipment was too high for young people to personally afford.

Consequently, although music was growing in popularity, young people could not afford records and audio equipment. This all changed with the appearance of the “radio cassette”. This machine could have been called a modern gramophone – a device incorporating a small-scale Compact Cassette tape recorder and a radio capable of FM reception together in one unit with an inbuilt amplifer and speaker.

This concept and the attractive price meant that it received tremendous backing as a personal audio device for young people.

It could reliably record FM broadcasts onto Compact Cassette and play them back quite simply for repeated listening. Such ease of use was one of the major advantages to this device. It continued to develop into a serious piece of sound equipment, successively incorporating stereo capabilities, loud volume, double cassettes and CDs.

The progress from radio to radio cassette player was one clear step in the personalisation of audio. The image of audio equipment for individual use shifted from that of tape recorders for recording or radios for information gathering to that of devices for enjoying music by oneself.

The radio cassette player progressed into a small-scale personal combo (a stereo for a child’s room); music recorded on Compact Cassette could be built up into a wealth of soft assets at the user’s disposal.