Popular Electronics – September 1978: The Golden Age of Audio
◆ Revised
Introduction
Vintage electronics magazines are far more than collections of old circuits and product advertisements. They capture moments when engineers, manufacturers and hobbyists were exploring ideas that would shape the audio equipment we now take for granted. Reading Popular Electronics from September 1978 is therefore less about nostalgia and more about discovering the origins of modern hi-fi design, integrated circuits and the transition towards increasingly sophisticated consumer electronics.
This issue is particularly rewarding because of its strong emphasis on audio. Alongside practical construction projects are detailed laboratory reviews, discussions of amplifier technology, new measurement standards and emerging recording media. The magazine also contains an editorial that reminds us many of today's software and intellectual property debates were already being discussed nearly half a century ago. Taken together, these articles provide a fascinating snapshot of an industry standing on the threshold of the digital age.
Rather than reproducing the magazine page by page, this review highlights the articles that remain most interesting to modern readers. Some demonstrate technologies that have become commonplace, others reveal engineering approaches that have stood the test of time, while a few simply capture the excitement of an era when building your own high-quality audio equipment was an achievable weekend project.
Magazine Features
Rather than reproducing the magazine's complete table of contents, the following articles stood out as particularly interesting from a modern perspective. While Popular Electronics covered a broad range of electronics topics, this issue has a noticeable emphasis on audio engineering, making it an excellent snapshot of hi-fi design during the late 1970s.
- Audio Amplifier Classes – Julian Hirsch explains the strengths and compromises of the major amplifier designs of the day, including Sony's pioneering work with Class-D amplification that would not become mainstream for decades.
- Build a Disco Preamp/Mixer – A practical construction project that demonstrates classic analogue signal flow. The circuit design remains an excellent study in audio engineering fundamentals despite advances in modern integrated electronics.
- Sony TA-N88 Basic Power Amplifier – Julian Hirsch's laboratory review of one of Sony's most technically ambitious power amplifiers provides a fascinating look at the engineering priorities of the era.
- A New IHF Standard for Amplifier Measurement – An insight into how the hi-fi industry attempted to standardise amplifier performance, making product comparisons more meaningful for consumers.
- Metal Cassette Tape Debuts – A glimpse into one of the most significant developments in cassette technology, explaining why metal tape was expected to revolutionise audio recording and playback.
- Build a Super Audio Filter – A practical DIY project designed to reduce hum in hi-fi systems, demonstrating the hands-on approach that defined hobby electronics magazines of the period.
- Experimenter's Corner – Forrest M. Mims begins a series on analogue-to-digital converters, reminding us that the digital revolution was already gathering momentum in 1978.
Beyond these highlights, the magazine also includes product reviews, amateur radio, computer programming, electronics construction projects and industry news, making this one of the most diverse issues of Popular Electronics from the late 1970s.
The Editor's Notes Revisited
In September 1978, editor Arthur P. Salsberg was already grappling with a question that still has no perfectly tidy answer: how should software be protected? He considered the limitations of patents, the relative simplicity of copyright registration, and the difficulty small developers faced when attempting to defend code that could be copied cheaply and distributed with little effort. What is striking today is not how dated the argument feels, but how familiar it remains. Software had barely become a mass-market industry, yet the essential tension between rewarding innovation and allowing ideas to circulate was already clearly visible.
Much of the technology has changed, but the dilemma has only expanded. Software is now distributed through downloads, subscriptions, cloud platforms, open-source repositories and mobile app stores, while ownership is complicated by licences, application programming interfaces and services that users never physically possess. Modern disputes over copied code, software patents, digital piracy and machine-generated programming all grow from the same underlying problem Salsberg identified: computer programs are both practical machines and reproducible expressions of human thought.
The editorial also captures the moment when software was beginning to be recognised as an industry worthy of protection in its own right. Salsberg's concern for the independent developer remains especially relevant. Large corporations can absorb legal costs and pursue infringement claims, while smaller creators often depend on trust, reputation and practical licensing rather than litigation. Nearly half a century later, the software-rights dilemma has not disappeared; it has simply grown alongside the value and reach of software itself.
Articles for the Modern Reader
Sony TA-N88 Class-D Power Amplifier
Of all the equipment featured in this issue, the Sony TA-N88 power amplifier was the product that immediately caught my attention. At first glance it appears to be another high-quality Japanese power amplifier from the late 1970s, but a closer look reveals something quite remarkable. Rather than using the conventional Class A, B or AB output stages common at the time, Sony had developed a pulse-width-modulated (PWM) Class-D amplifier capable of delivering 160 watts per channel while occupying considerably less space than many competing designs. To a modern reader, this is astonishing because Class-D amplification is often regarded as a technology of the twenty-first century, yet Sony was already demonstrating its potential almost fifty years ago.
The accompanying technical article provides an excellent explanation of how the amplifier operates. Instead of continuously varying the output transistors, the incoming analogue signal is converted into a high-frequency pulse-width-modulated waveform that switches the output devices fully on or fully off. After passing through a low-pass filter, the original audio signal is reconstructed and delivered to the loudspeakers. The magazine's block diagrams remain surprisingly easy to follow today and provide one of the clearest explanations of early Class-D amplifier design that I have encountered in a consumer electronics publication. They also demonstrate just how much engineering innovation was occurring behind the scenes during the late 1970s.
Sony paired this switching output stage with an equally innovative high-frequency switching power supply operating at around 20 kHz, reducing the size and weight of the transformer and filter capacitors compared with conventional linear supplies. The laboratory measurements published by Hirsch-Houck Laboratories confirmed that the amplifier comfortably achieved its rated output while remaining impressively cool in operation. The reviewers were clearly excited not simply by its measured performance, but by what it represented: a glimpse into the future of compact, high-power audio amplification.
Looking back with nearly five decades of hindsight, the article is equally interesting for its discussion of the amplifier's limitations. The reviewers noted that the switching circuitry generated radio-frequency interference under certain conditions, occasionally producing audible interference in nearby AM and FM receivers. This is a familiar challenge to modern Class-D designers, who devote considerable attention to PCB layout, electromagnetic shielding and output filtering. Semiconductor technology, switching devices and digital control techniques have improved dramatically since 1978, solving many of these early shortcomings while preserving the efficiency advantages that made the concept so attractive in the first place.
More than anything, the Sony TA-N88 demonstrates that many of today's "modern" technologies have surprisingly deep historical roots. Reading this review, it becomes clear that Sony's engineers had already recognised the enormous potential of efficient switching amplifiers decades before they became commonplace in home theatre receivers, powered loudspeakers and compact desktop amplifiers. For AudioPhil, this was undoubtedly the standout discovery in the entire magazine—a reminder that the future of audio often arrives much earlier than history gives it credit for.
Build a Disco Preamp/Mixer
One of the most enjoyable discoveries in this issue is the construction article for a complete disco preamplifier and mixer. While the name immediately conjures images of mirror balls and dance floors, the underlying design is surprisingly sophisticated. The project combines phono preamplifiers, microphone inputs, auxiliary inputs, monitoring, tone controls and a flexible mixing section into a single integrated design using the latest operational amplifiers of the day. It represents a time when electronics magazines didn't simply review equipment—they taught readers how to build professional quality hardware themselves.
What impressed me most was the block diagram rather than the finished circuit. Viewed through modern eyes, the signal flow remains almost timeless. Every source is first conditioned by an input stage, normalised to a common operating level, mixed, monitored, processed through tone controls and finally buffered to the output. Whether implemented with analogue operational amplifiers in 1978 or digital signal processors today, this same architecture still forms the basis of modern mixing consoles, audio interfaces and software digital audio workstations. Good signal-flow design simply doesn't go out of fashion.
Naturally, many of the implementation details have changed over the last fifty years. Today's designers would probably replace much of the analogue switching with electronic switching or microcontroller control, use low-noise surface-mount operational amplifiers, employ switch-mode power supplies and perhaps integrate digital equalisation, USB audio and DSP effects. The large collection of discrete potentiometers, switches and through-hole components would also give way to compact integrated assemblies. Even so, the engineering principles demonstrated throughout the article remain every bit as relevant as they were when first published.
For today's electronics enthusiast, this project is less about building a disco mixer and more about understanding classic analogue audio design. The beautifully presented block diagrams and clearly separated functional stages make it an excellent educational reference for anyone interested in audio electronics. In fact, readers looking for a modern companion project may also enjoy the Lepai LP-2020TI Class-D Amplifier, which demonstrates how compact switching amplifiers have carried many of these same audio design principles into the twenty-first century.
Other Notes
Phase Linear Power Amplifier - The new Model 400 Series Two aplifier has a rated power output of 210 watts rms/channel into 8Ω over 20-20,000Hz with no more than 0.09% THD. It has a BI-FET high-loop gain ciruitry and electronic energy limiters said to prevent overload damage. Dual peak-reading LED meters and twin input sensitivity controls are mounted on the front panel. RRP$599.95
Universal Tonearm Shell - A Universal tonearm shell, the AT-N, has was introduced by Audio-Technical. The shell is said to mate with virtually all Japanese and most European tonearms. The AT-N facilitates changing cartridges with more than one is used. RRP$5.95
Desktop Executive Entertainment Center - Douglas Dunhill Inc. advertisement RRP$199.95. I was inspired to give this concept my own treatment in ReicherTek Solaris the desktop entertainment Hi-Fi concept.
Organtua - PAiA advertisement - Organtua has three individual ranks (each with 5 position octave select switches) for a rich, thick sound. RRP$279.95.
Conclusion
Nearly fifty years after publication, Popular Electronics – September 1978 remains a remarkably engaging read. While component technology has evolved beyond recognition, many of the engineering principles discussed throughout the magazine remain surprisingly familiar. Signal flow, amplifier design, laboratory testing, analogue audio and careful system architecture are every bit as relevant today as they were when these pages first reached subscribers.
For me, the standout discovery was not a single product but the realisation that many technologies we think of as "modern" have much deeper roots than expected. Sony's early Class-D amplifier, the thoughtfully designed disco mixer, evolving amplifier measurement standards and even the editor's discussion on software rights all demonstrate that the electronics industry has been solving many of today's problems for decades. Looking back through these magazines gives today's enthusiasts valuable historical context that simply cannot be found in contemporary product reviews.
If this journey through Popular Electronics has sparked your interest in vintage audio, continue your exploration with Electronics World, February 1970. That issue examines one of hi-fi's most ambitious ideas—the arrival of four-channel (quadraphonic) sound—and captures the industry's enthusiasm for creating a more immersive listening experience. Read together, these two magazines reveal how rapidly consumer audio evolved throughout the 1970s and how many of the innovations we enjoy today were already taking shape decades ago.
Read the Original Magazine
This article explores some of the most interesting audio features from Popular Electronics, September 1978. If you would like to browse the complete magazine, you can read it below thanks to the Internet Archive. Use the toolbar to zoom, search and navigate through each page.
Scanned and preserved by the Internet Archive .
Curator's Notes
Reader Guide
The following material expands on the terminology, historical context, technical concepts, and related reading connected to this article.
Glossary
- Hi-Fi (High Fidelity)
- A term widely used from the 1950s through the 1980s to describe audio equipment capable of reproducing sound with high accuracy and low distortion. While still recognised today, the abbreviation "hi-fi" has largely been replaced by terms such as high-end audio, audiophile equipment or simply home audio.
- Class-D Amplifier
- A high-efficiency power amplifier that reproduces analogue audio by rapidly switching its output transistors fully on and fully off using pulse-width modulation (PWM). After the switching waveform passes through a low-pass filter, the original audio signal is reconstructed and delivered to the loudspeakers. Although Class-D amplifiers are often associated with compact modern hi-fi systems, Bluetooth speakers and powered studio monitors, the underlying concept dates back much further. Sony's TA-N88, featured in this issue of Popular Electronics, demonstrates that commercial Class-D designs were already being explored in the late 1970s. Early implementations faced challenges with radio-frequency interference and switching technology, but advances in semiconductor devices and digital control have since made Class-D the dominant amplifier topology for many modern audio products.
- Component System
- A complete hi-fi system assembled from separate components such as an amplifier, tuner, cassette deck, turntable and speakers. Enthusiasts could mix and match equipment to suit their preferences, in contrast to the all-in-one music systems that became popular during the 1980s and the integrated streaming systems common today.
- Function Block Diagram
- A simplified engineering diagram that shows how signals or information flow through a system by dividing it into functional stages rather than individual electronic components. Each block performs a specific task—such as amplification, filtering, mixing or buffering—with arrows indicating the direction of signal flow. Function block diagrams are invaluable during the early design phase because they allow engineers to understand and refine the overall architecture before developing detailed circuit schematics. Even today, complex products ranging from audio mixers and amplifiers to spacecraft, industrial control systems and software applications are typically conceived first as function block diagrams before progressing to detailed implementation.
- Pre-amplifier (Pre-Amp)
- An electronic circuit that prepares low-level audio signals before they are sent to a power amplifier. A pre-amplifier typically provides input selection, volume and tone controls, signal buffering, and in some cases specialised inputs such as a phono stage for turntables. Because devices like microphones and magnetic cartridges produce signals measured in millivolts, a pre-amplifier raises them to a standard line level while minimising noise and distortion. During the hi-fi boom of the 1970s, high-quality systems often used separate pre-amplifiers and power amplifiers to maximise performance and flexibility, although today both stages are commonly integrated into a single amplifier or even a compact digital audio device.
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References
The following document was referred to when developing this article.
- Popular Electronics, Ziff-Davis Publishing Company, September 1978
Disclosure
This article is provided for historical, educational, and entertainment purposes. Product names, trademarks, and copyrighted material are acknowledged as the property of their respective owners. Opinions expressed are those of the author based on personal experience and research, and no affiliation with or endorsement by the original creators or rights holders is implied.