An Interview with Paul Penfield Jr.


Oral History – Paul Penfield Jr.




Ektachrome Copyright © 1956 by Paul Penfield Jr.


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.




Oral History – Paul Penfield Jr.



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






COPYRIGHT © 2003 by Jack Ward.  All Rights Reserved.