Elektor Electronics Publishing, PO Box 1414, Dorchester, Dorset, DT2 8YH, England.
I really enjoy browsing (in the reading sense) through circuit applications books. The Elektor 300-series of circuit ideas runs the complete gamut of electronics applications. Each July/August issue of Elektor Electronics magazine represents their annual "summer circuits" issue, which is a compendium of the projects published in the preceding year. The 300-series books are a selection of the most interesting articles from a number of preceding "summer circuits" issues.
The first stop in reading these books should be the "decoder" page. Elektor uses some shorthand for devices used in the schematics, such as "TUN" (transistor, universal NPN), and lists some recommended device part numbers. They use the European codes for resistance, capacitance, and inductance (also adapted by all Audio Amateur publications).
For instance, rather than 2.7k, you will find 2k7.
One oddity (to me) is the use of "U" for voltage rather than "V." "U" is a common designation for integrated circuits here, while Elektor uses IC (also used in the US) as well as "N" for logic gates. All connectors are labeled "K" (which we use for relays) rather than "J" and "P," but it is all well-explained in the decoder.
High voltages are indicated by skull-and crossbones, and there is a section in each book called "Warning! Electricity Can Be Dangerous." Some of the devices used in these projects are from European suppliers such as Ferranti, Philips, and Siemens, and may be difficult to track down here in the US.
The experienced hobbyist should be able to substitute a more common domestic part. Some of the circuits will not work in this country due to different video standards (PAL and SECAM versus NTSC). While all the power supplies are based on a mains voltage of 230V AC, 50Hz, Elektor specifies the secondary voltages for the project power transformers, making it easy to select one for our 120V AC, 60Hz utility standard.
Author credits are listed for most of the circuits, and some are taken from the application notes of component manufacturers. There are also some that have no credit, so I assume Elektor developed these circuits themselves.
The Books
301 Circuits was first published in 1983. My review copy is the 1996 reprint, which is the sixth for this popular book.
Given the vintage of the original circuits, I found some for which the IC is no longer available, such as the pA739 dual op amp and the MK50398N counter driver IC. The 741 op amp abounds, as do references to the "Disco" craze. It is a very interesting snapshot of electronics in that era. Elektor pro vides an appendix of device out lines, schematics, and limited performance specs for all the referenced semiconductors and ICs.
The audio projects are primarily guitar effects, and the few labeled "hi-fi" simply aren't. Solid-state audio was not at its best in 1983.
The book contains only a table of contents for the circuits; no alphabetical index is provided. Finding a particular circuit out of 301 will be more difficult in this book than in the subsequent 300-series books, which have proper indices, but this does not detract from 301's usefulness.
302 Circuits (1985) is in its fifth reprint, dated 1994.
In addition to the circuit schematics, some of the projects have PC board layouts and stuffing guides.
The circuits are listed in alphanumeric order in the following categories:
Audio, music, and sound generation
Cars and bicycles
Computers and microprocessors
Design ideas
Generators and oscillators
Hobby and games
Home and garden
Miscellaneous
Power supplies and battery chargers
RF and video
Test and measurement
There are 33 audio projects-more than 10% of the total.
One of them is a safety switch for stereo equipment, in tended to solve a problem I never realized existed: "Well over half the damage to homes through fire is caused by domestic equipment being left on for excessive periods of time. Stereo equipment is only one of the many items which are easily forgotten about. If the simple circuit described here is incorporated into the stereo equipment, or the television set for that matter, there will be no need to worry about these items being the cause for a rude, smoky awakening in the small hours." I would think most of the homes with high-end Class-A audio amplification, and every college dorm and teenager's room would be in immediate need of this device! Of course, all the computer projects were written around the models available back then, such as the Apple II and Commodore 64.
303 Circuits (1988), fourth reprint 1996, provides the device outlines and PC board layouts with the project schematics, rather than in a separate appendix. Some of the projects include assembly sketches. There are 32 audio and hi-fi projects in the book.
For the most part, the audio circuits use high-quality parts and power-supply designs. There are some interesting discrete power amplifiers, although other amplifiers use the then newly available TO-220 power amplifier IC packages, which are now widely used in car stereo and computer speakers, but I don't consider them "hi-fi." The computer projects are still based on 8-bit units-another interesting time capsule of 40-track 5 1/4" floppies, 2MHz processors, and cassette-tape storage.
The "generators and oscillators" topic is now part of the test-equipment section, and a new section called "electro phonics" was added to cover guitars, effects, synthesizers, and disco projects.
304 Circuits (1991) brings us into the "90s, with a second 1995 reprint. The audio projects use higher-quality parts and more analog LSI building blocks, and we find the first computer projects for the IBM-PC. There are 35 audio projects, and the 11 contents categories have changed again:
Audio and video
HF Hobby Home and garden
Music/electrophonics
Computers/ microprocessors
Generators/oscillators
Test and measurement
Power supplies
Car electronics
Miscellaneous
In addition to the assembly sketches, the book includes some photographs. All the drawings and photographs are of high quality.
305 Circuits was originally published in 1994, and I reviewed the 1995 reprint.
The projects range from fairly simple circuits for use in the home to complex ones such as communications receivers and computer "adjuncts." A couple of circuits contained descriptions of operation that were insufficient for a beginner to understand how the circuit functioned.
There are only six circuit categories now:
Audio and hi-fi
Computers and microprocessors
Power supplies and battery chargers
Radio and television
Test and measurement
General interest
The 30 audio circuits include low noise preamps, power amplifiers, filters, compressor-limiters, and so on. The computer projects are mostly aimed at the IBM-PC, but a few 8-bit projects are still listed. Time and technology marches nicely along.
306 Circuits (19906) is the final book in the series. The format is essentially the same as 305 Circuits. "HF" replaces the "radio and television" category, and there are four "supplement" projects. In addition to conventional circuits, the 55 audio projects include lots of active filter designs, up to tenth order! Conclusion These six books represent a valuable collection of over 1,800 projects, design ideas, and concepts. It is always interesting to see how others solve practical circuit problems. Like all general collections, some are clever, some obvious, some overly complex, and a few only marginally useful.
Elektor has made a real effort to eliminate errors in the circuit diagrams, and I could not find any that I believed would not work at all.
While only a fraction of the circuits are devoted to audio, the others are just as interesting and cover a wide range of subjects. I have placed this collection next to my five volumes of the Encyclopedia of Electronic Circuits (TAB Books) for ready reference.
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