A major figure in the audio field, Dr. William Marshall Leach Jr., passed away recently. Anyone familiar with audio electronics design is sure to be familiar with his work.
A teacher of electrical engineering at Georgia Tech Institute of Technology, Dr. Leach was considered an outstanding professor by his students. He was also an author, and shared his knowledge and passion for audio engineering with a much wider audience through published magazine articles and with a book ("Introduction to Electroacoustics and Audio Amplifier Design").
In fact it was one of his early articles - published in Audio magazine back in the 1970s - that helped inspire me (and countless others I'm sure) to eventually pursue an EE degree. The article - "Build a Low TIM Amplifier" - described an audio amplifier design, complete with parts and board layout, that any DIY-inclined audiophile would find hard to resist.
At the time, transient intermodulation distortion (TIM) - thought to have been responsible for the "harsh" sound of many early transistor amplifiers - had become a major concern among solid-state amplifier designers. Leach's amplifier avoided the problem through, among other things, optimization of open-loop bandwidth and the judicious use of overall negative feedback.
The Leach amp was one of my first DIY audio projects and Professor Leach's article was a great help in learning about audio design. I also learned another lesson as well.
During one of my early listening sessions with the amp I was suddenly startled by a loud gunshot-like "bang!" followed immediately by the sound of a projectile hitting the ceiling of the room. As readers of this blog have no doubt already guessed, the mystery object turned out to be a small power supply rail capacitor that had been accidentally reverse installed. This of course was the fault of yours truly and not the designer of the amp.
Despite this minor incident (the amp was unscathed), the Leach amp (along with another DIY amp project - a single-ended Class-A amp designed by Nelson Pass) went on to serve me well for many years. Its designer will be sorely missed.
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