28 May 2004

Friedrichs, Peter. Instruments of Amplification. Fun With Homemade Tubes, Transistors, and More. 2003. ISBN 0-9671905-1-7. 297 pages.

Reviewed by Sheldon Greaves

Click here to order this book from the SAS Online Store.

 

Figure 1. "Microphonic Relay" built from pieces of an old telephone headset, copper pipe fittings, some threaded rod, a bit of steel, and a wooden base. Click image to enlarge.

Recently it was my pleasure to review Pete Friedrich's remarkable self-published volume The Voice of the Crystal (hereafter VotC), which describes how to make working radio receiver components entirely from scratch. That book is part of a recent revival of crystal radio technology among radio and science enthusiasts. VotC covers the construction of radios with the same spirit, if not the same methods, used by early radio experimenters.

In my view if VotC represents a revival, Friedrich's latest book, Instruments of Amplification, represents a minor revolution. Many amateur scientists labor under the assumption that there are certain things that are simply beyond the capability of the home experimenter. In many cases, this is both true and prudent; one can spend inordinate amounts of money or even endanger ones' health by trying to reproduce technologies that are cheaply available off the shelf or simply ought not to be trifled with.

"Balance Beam Amplifier" made of carbon and graphite electrodes, brought into contact by a delicate balance and modulated by the vibration of a steel diaphragmClick image to enlarge.

I had always assumed that vacuum tubes and transistors were among those things that were outside the bounds of the amateur scientist. This brings us to the book's subtitle: Fun With Homemade Tubes, Transistors, and More .

Instruments of Amplification picks up where VotC left off. Although Instruments is a wonderful read even if you haven't read VotC, the two books really belong together. Friedrichs shows you how to build devices that can amplify the signals pulled in by a crystal set, while at the same time giving a remarkably lucid treatise on what amplification is and how it works. The book begins with an excellent explanation of the nature of amplification; what it is and what it is not. The early projects are fairly simple devices, such as a telephonic relay built from parts taken from an old telephone handset (see Fig. 1) . Another is the "balance beam amplifier" which, although simple conceptually, seems challenging to build (Fig. 2).

 

"Bell Jar Audion" modeled after the Audion of old, this tube features planar construction, and brass electrodes. Click image to enlarge.

But then, after an excellent section on impedance, we move into vacuum tube technology; glow tubes, diodes, audions and triodes. These chapters include a very solid introduction to vacuum pumps and vacuum technology for the home experimenter. It's a bit of a side trip, but a very interesting and useful one. I confess that the part of the book describing tubes was my favorite, if only for the sheer chutzpah of someone successfully building something that is both "obsolete" and supposedly beyond the home experimenter. And as if that weren't enough, Friedrichs finishes the book with a section on home semiconductors, homebrew transistors, and some good information on power supplies.

One might ask, "Why bother?" If you read my previous review of VotC, you should already know the answer, but let me briefly reiterate. Building scientific equipment from the ground up requires a more rigorous intellectual effort that ultimately yields richer rewards. It is by starting from first principles that we best learn how and why things work.

 

The Tennis Ball Triode "in action". The base is composed of a cheap, glass ashtray. Click image to enlarge.

Throughout this book the authors explains concepts and projects with the same outstanding level of clarity that we have come to expect from his earlier book. Another aspect of his work that I very much enjoy is the way he leaves his projects open; most of his chapters close with ideas about how one might expand on what he has done and go further. Indeed, if you visit the online photo gallery associated with this book, you'll find pictures of many projects that are not mentioned in Instruments.

Earlier I said that this book was revolutionary. I make that claim because Friedrichs has given us a glimpse of how far we can push existing technology and find ourselves doing and building things that were thought to be beyond the scope of amateur scientists. Making a vacuum triode out of an ashtray and a votive candle holder qualifies, I think, as pushing the envelope. This is truly an inspiring, instructive, delightful book.