Guitar Amplifier Design: Tubes and Semiconductors Play Together
by Ulrich Neumann
Guitar Amplifier Design: Tubes and Semiconductors Play Together is a look over the shoulder during the process of designing a unique guitar amplifier. Insights and opinions on design principles and best-practices for getting great tone in any design. Novel approaches and solutions to common circuit-design problems. Performance and tone improvements for common tube circuits. Explanations of cause-effect relationships that lead to better designs and better tone.
Dr. Ulrich Neumann is a professor of Computer Science, with a joint appointment in Electrical Engineering, at the University of Southern California in Los Angeles. He completed a Bachelors and Masters degree in Electrical Engineering from the State University of New York at Buffalo and was granted a computer science Ph.D at the University of North Carolina at Chapel hill. His academic research relates to Computer Graphics and Computer Vision.
He received an NSF CAREER award. He was an Associate Editor for the IEEE Transactions on Multimedia. He Held the Charles Lee Powel Chair of Computer Science and ELectrical Engineering, and was the Director of the Integrated Media Systems Center (IMSC), an NSF Engineering Research Center (ERC). Prof. Neumann teaches classes on Computer Graphics and Music Amplifier Circuits.
In his commercial career, he designed multiprocessor graphics and DSP systems, cofounded three companies, and independently developed and licensed technologies. He is the inventor on six granted US patents.
His musical background is in piano and guitar. He has pursued a passion for amplifiers and music throughout his life and this book reflects his accumulated experience in circuit design and tone shaping. He enjoys playing the amplifiers he builds.
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A ground-breaking approach to modern state-of-the-art Guitar Amplifier Design – a “must-read” deserving of a place on your reference book shelf.
There’s an old adage that says “You can’t judge a book by its cover”. If you took a quick look and decided to give it a pass, concluding that cartoon characters on the front cover don’t spell “serious” - you missed the boat. Take another look - Vacuum Tubes and Semiconductors “playing” together in a Guitar Amplifier - this book is ground-breaking in its approach to the design of a modern state-of-the-art guitar amplifier.
There are numerous books on the market which discuss and dissect designs from the tube amps of the 50’s to the digital modelling amps of today – this isn’t one of them. In this book, the author starts with a blank sheet of paper and the premise that “tubes and semiconductors are complimentary and used together provide a powerful suite of solutions to achieving his Guitar Amplifier Design goals and objectives.”
Step back for a moment and consider the statement “Any good electric guitar amplifier is designed to produce distortion”.
Many players consider solid-state amplifiers to sound “thin, lifeless and buzzy”, preferring tube amplifiers specifically for the characteristic overdrive distortion which can be produced by their vacuum tube circuits. That said however there are applications within an amplifier in which today’s semiconductor technology can clearly outperform that provided by tube technology. What then if one selects applications and combines optimum choices from among the palette of available options which technology provides? Semiconductors for signal amplification, vacuum tubes for overdrive, tone, colour and presence.
This is the approach taken by Neumann as he carefully walks the reader stage-by-stage through his design process, from input, through tone and phase inverter, to output, using interconnected vacuum tube and semiconductor technology to achieve his end goal. But there’s more.
Remember the weight of your existing amp? Why is it so heavy? The answer of course lies in the fact that it utilises at least two transformers mounted on a steel chassis. What if one could eliminate the transformers and build the amp in a lighter weight aluminium chassis? Well, by adopting a switching power supply and an AOT (Active Output Transformer) design using active components to mimic the behaviour of an output transformer, the author has done just that. How about a finished 100W amp weighing less than 7 lbs?
Even if you don't decide to build one of these amplifiers, this book will open your eyes to the “art of possible” and why technology integration should be considered. This is your opportunity for a first-hand preview of what the next generation of guitar amplifiers are going to look like.
The bottom line for anyone with an interest in guitar amplifiers is that this book, “Guitar Amplifier Design” is a “must-read”, deserving of a place on your reference book shelf.
Conclusion: When looking for a book to buy and read, the first thing that probably grabs your attention is the cover. If the cover appears uninteresting you will probably conclude that the book is not for you and move on. However, if you open the book up and read what is inside, you may find it pretty interesting after all. The old adage is correct – outward appearances are not a reliable indication of that which resides within.
Footnote: I previously purchased and very much enjoyed reading an earlier 2015 book by Ulrich Neumann and Malcolm Irving, entitled “Guitar Amplifier Overdrive – A Visual Tour”. It currently resides on my reference book shelf.
Armed with this knowledge, and what ever she thought of the cover, my wife purchased “Guitar Amplifier Design” giving it to me as a Christmas gift. I’m very glad she did. It is indeed a “serious” book. It too has earned its place on my reference book shelf.
David R. Anderson, P.Eng.
April 2020
This book explains it ALL! Sort of like a grand unified theory of ampdom. I am re-reading it as it contains the best explanations I have read.