Page 42 - The Art and Science of Analog Circuit Design

Barry Harvey

Figure 3-6.
The electronics of the previous radio. Because this set was not of the highest caliber, the electronics are humble
and have no precious elements. From the John Eckland Collection, Palo Alto, California. Photo by Caleb Brown.

the chopper-stabilized op amp was very accurate, it was expensive and
the chopper could wear out, being a mechanical vibrator. The uncertainty
of transistor Vbe was really negligible, relative to supply voltages, and
biasing transistors was a snap, although not widely understood then.
Transistors could seemingly do anything that didn't involve too much
power. But until perhaps 1966, if you had to handle power with a transis-
tor, you used a cow of a germanium device.
But between 1961 and 1967, the choice of transistor or tube was often
made by the prejudice of the designer. Some applications demanded one
device or the other, but in the case of audio amplifiers, there was free
choice.
Construction of electronics changed radically in this time. Tubes were
mounted in sockets whose lugs served as the supports for components,
and a solid steel chassis supported the circuits. Steel was necessary, since
the tubes couldn't tolerate mechanical vibration and the massive power
supplies needed support. The most elegant construction was found in
Tektronics oscilloscopes. They used molded ceramic terminal strips to
support components, and only about eight components could be soldered
into a pair of terminal strips. Cheaper products used Bakelite strips.
These were all rather three-dimensional soldered assemblies: point-to-
point wiring literally meant a carpet of components connected to each
other and to tubes in space. The assemblies were also very three dimen-
sional; the tubes sprouted vertically above the chassis by three to five

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