This book is an excellent reference for many different vacuum tubes. Particularly tubes that were used in guitar amplifiers, and those which played an important role in shaping the modern tube sound. General terms, basics, & tube manufacturers are included in this edition. (12AT7, 12AU7, 12AX7, 57515Y3, 6550, 6AQ5, 6BQ5, 6L6, 6P14P, 6SN7, 6V6, 7199, Amperex Electronic, ECC81, ECC83, EF86, EL34, EL84, Electro-Harmonix, General Electric, KT66, KT88, KT90, and much more.)