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Oral History – Paul Penfield Jr.
(Continued)
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Ektachrome Copyright © 1956 by Paul
Penfield Jr.
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Above is an updated
version of the cover of the August
1956 issue of Radio and Television News magazine, which featured an article
written by Paul describing construction plans for a “Transistorized Beach Phonograph”. As Paul recounts in this Oral History,
he would develop an idea for a project, design and build a working model,
write an article describing his work, take photos, and submit to a magazine
for publication. In this article,
Paul’s project phonograph was featured on the front cover of the magazine.
(Paul notes that the two beach-goers in the photo were his friends, George
Kidder, later a distinguished biology professor, and his sister, Beverly
Kidder.) The article was three pages in length, and probably earned Paul
$100 or so, which helped with the MIT tuition payments. The phonograph used four germanium
transistors and a mechanical “wind up” turntable in order to minimize the
number (and weight) of the batteries required to operate this early
portable entertainment system.
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Oral History – Paul Penfield Jr.
(Continued)
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You
wrote quite a few articles on the early use of transistors in audio.
Well, not just audio. I was interested in other aspects of
transistors as well. Transistors at
that time could not be used much above audio frequencies. These were all
germanium transistors (the ones I used were mostly PNP). Silicon
transistors weren’t available yet.
And, NPN transistors, because of the higher mobility of the
electrons, could go to a higher frequency, but people weren’t making NPN
much at the time, because these were more difficult to make. So, the transistors I used were
basically good through audio frequencies, and maybe through ultrasound, but
not up to radio frequencies.
I
noticed a very extensive series of more than 20 articles on different aspects
of transistors in audio applications you wrote for Audiocraft magazine,
beginning in 1956 and ending in 1958.
This would seem to be a very comprehensive view of early transistor
audio.
That’s right. I did a whole
series that I intended to be comprehensive, and that might take the form of
a good, solid book on this subject.
Go
To Penfield Oral History, Page 6
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