11.6.2.2 - THE ELECTRO ACOUSTICAL AGE
The first all electronic volume and tone controls appeared in the market around 1928. Therefore, considering the sound sources was restricted to the phonographic disc and the broadcasting transmissions, the domestic sound reproducer consisted in an association of the radio receiver and the recorder changer only.
Fig. 341 - Loftin - White amplifying circuit topology.

In this technological stage of the sound amplification, the engineers introduced new types of circuit topology as the Loftin-White system using triode valves as type 224 and 245.
Basically it consists in a direct coupling between the valve grid-plate allowing distorsion free amplification in a frequency range from 50 upt to 10000 Hz. Fig 342
Soon new innovations were introduced such as, the dynamic loudspeaker, the new pentode valves, as well as advanced electromechanical phono pickup where the stylus was assembled over a transducer using La Rocehelle salt.
Before WWI, the new advanced sound reproducers were launched in the market as the ones made by the American manufactures such as E.H.Scott and McMurdo Silver. Fig 342.
Among them the model Quaranta is the most famous one. In the reality it is an electro acoustical system comprising the radio frequency and amplifying stages using circa 40 valves, the recorder changer and a set of loudspeakers assembled separately in two attractive wooden made cabinets.
Fig. 342 - The combined radioreceiver and the phonograph reproducer made circa 1938. The apparatus comprises the radioreceiver, the loudspeaker system and the recorder changer assembled in an attractive wooden made cabinet. Due to the high quality and improved craftsmanship the American manufacturer E. H. Scott is the most famous one.
As aforementioned, pressed by the enormous producing capacity required by the war efforts, at the end of WWII the industry looked for new trends in the consumer market by lauching high quality home sound reproducers.
Thus, it gave birth to the Hi Fidelity age, which for historical allocation purpose started in 1948, when in England N.D.T. Williamson developed his famous amplification circuit.
Innovations like the microgroove record and the frequency modulation broadcasting pressed the industry to develop new tehcnical releases, which arose a new home applicance trend, i.e. the Hi-Fidelity modular sound system comprising the combined amplifier-FM tuner, the recorder changer provide with phono pickup and the speaker enclosure. Fig. 343
The Hi-Fidelity boom allows the surgence of many brands in the market and in this way to become more competitive some manufacturers launched in the market cheaper semi factory assembled kts. They were supplied with detailed friendly instruction manuals, which improved so much the kit assembling for the enduser with a small knowledge of electronics.
Even considering the same conceptive origin the Edison phonograph and the Telephone had differents performance regarding their evolution. While the former was a great success since the beginning, as a prospective invention the telephone acceptance by the public was quite slow.
Therefore, the invention of the telephone was not inspired in the popular requirements only, but more for the ingenuity and the great discern of its inventor A. Bell, who after by-pass many difficulties launched the basis for the electrical transmission of the spoken word on wires.

Fig 343 - High quality separated pre and power amplifer unit model QUAD II made in England circa mid-fifities.