This book presents vacuum tube amplifier theory using modern, web-based design tools and computer visualizations to eliminate the usual litany of mathematical formulas. The book begins with the fundamentals of electronics and vacuum tubes. It then proceeds through each stage of a modern guitar amplifier, including preamp voltage amplification stages, cathode followers, tone stacks, power amps, phase inverters, and power supplies. The final chapter is devoted to the craft of controlling overdrive dynamics and harmonic distortion.