Vacuum-tube (or valve, depending upon which side of the pond you live on) technology spawned the Age of Electronics early in the 20th Century. Until the advent of solid-state electronics near mid-century, hollow-state devices were the only choice. But following the invention of the transistor (after their process fell to reasonable levels), within a couple of decades, the death of vacuum tubes was widely heralded. Yet here we are some five decades later, and hollow-state equipment is enjoying something of a comeback, especially in the music and high-end audio industries. Many issues surround hollow-state audio: ? Does it produce?as some claim?better sound? If so, is there science to back up these claims? ? How do hollow-state circuits work? ? How do you design hollow-state audio circuits? ? If hollow-state equipment fails, how do you go about troubleshooting and repairing it? ? Can we recreate some of the classic hollow-state audio devices for modern listening rooms and recording studios? ? How can we intelligently modify hollow-state amplifiers to our taste? These and other topics are covered in The State of Hollow-State Audio.
