|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
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.
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.
|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
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