Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, Third Edition

This book moves beyond general principles of tube amplifier design to carry out an intense examination of one of the most famous circuits of the rock era. The book begins with the 5F6A's relatively simple triode preamps (bypassed cathode resistor, unbypassed cathode resistor, and cathode follower) and then progresses through the mathematically challenging tone stack, long-tailed-pair phase splitter, and push-pull power amp. Every formula for every tube is derived in all its gory detail. The author's methods include the classic load lines and composite characteristic curves of the Radiotron Designer's Handbook as well as more modern techniques like linear regression and the Discrete Fourier Transform. Special attention is paid to quantifying the push-pull amplifier's nonlinear response and to analyzing power supply voltage sag as it reacts over time.

This expanded, third edition conducts the first-ever full-scale investigation into the dynamics of the power amp when severely overdriven. The new edition also extends the heritage of the Fender Bassman 5F6A by examining the modifications Marshall incorporated into its JTM-45, Bluesbreaker Combo, and Plexi amplifiers. It includes an additional fold-out schematic of a Generalized Fender-Marshall Amplifier Circuit highlighting the differences and commonalities between these four Titans of Rock. Marshall's circuit modifications give its amps a completely different sound, unique dynamics, and a separate place in history. The commonalities with the 5F6A, however, are also quite striking. Given a universe of possible modifications to these circuits, it is enlightening to know where and why Marshall chose to focus its innovation.

The Bassman 5F6A circuit has inspired guitar amplifier designs for five decades, so sharpen your pencil, fire up your calculator, and find out what makes this amp rock!