The
invention of the digital VUmeters
(Bar Graph Display)
50
years creating technology for
audio level measurement
The original
invention arises in 1959, before Solidyne was founded. We have been working
in film sound recording. This technique uses a light beam moved by means
of a galvanometer. The control of the peaks of audio was very strict and
the needle VU meters do not have enough fast action. Then, a system of
optical lens was necessary to set the correct recording level, using a
microscope of difficult reading, to see the light beam.
The solution
we found was an electronic system, without mechanical parts, formed by
10 steps marked in decibels. We created therefore the first light bar
VU meter, without inertia and over impulse, that measures the true peak
of the audio signal
Since
LEDs had still not been invented, each indicator was illuminated by a small
neon lamp; that was placed in the back part of the VU meter and was handled
with 250 volts from a tetrode tube.
From 1962
we replaced the neon illuminators by incandescent lamps used in telephony,
of very long useful life. You can see in this console of 1967 the use
of bar graph VU meters, which were excited by transistors
At
the beginning of the decade of 1970 Solidyne manufactures equipments with
the new bar VU meters, like this audio compressor for AM radio.
The
indication of the input and output levels, as well as the compression level,
was given with great exactitude by the bar graph VU meters. The scale was
linear in dB. For that time no other manufacturer of the world used this
technology
When
reliable LEDs reaches the market, we start manufacturing the 3rd generation
of bar graph displays; that were used in 16 and 24 channels consoles for
recording studios, as this unit of 1976
This console
2000X of 1978, for 16 channels recording, uses a complete turret with
24 VU of modular construction, that supported different ways of reading
(peak, average, rms)
At that time,
our patent was expired, and this device began to be used for a lot of
companies of USA and Japan, in professional products and home audio. The
manufacturers of integrated circuits began to produce units to excite
the LEDs.
At this moment,
the evolution of our ideas derives in the concept of the Integrated Display
VC180, which indicates not only the peak level of a stereo signal but
the stereo Vector of Phase. Available from 1997 to the present time, this
technology allows the user interpreting an audio signal in a total way.
Brief History of Solidyne
The invention of the bar-graph display
