They impart a warm, rich sound—some may call it "coloured"—that softens the harsh brightness often associated with transistor-based gear. You can use the terms tubes, vacuum tubes, or valves interchangeably.

Until the 1960s, valves dominated many electronic devices, including home stereos, car radios, cinema amplifiers, guitar amps, tape machines, and televisions. However, as Japanese manufacturers embraced transistors, gear became more compact, durable, and cost-effective, leading to the decline of valve production.

The golden era of valve manufacturing spanned the 1940s–1960s, with vast quantities produced worldwide—many designed for specific applications. Since they are sealed in a vacuum, they tend to remain stable for years if stored properly (unless compromised by a gas leak). Even today, some countries continue using valves in military and medical equipment.

Despite technological shifts, several audio manufacturers have persisted—or returned to—valve amplifiers, whether in preamps, power amps, or integrated systems. Many audiophiles believe that vinyl combined with tube gear delivers a more authentic sound, and it's hard to disagree. Some of the best-sounding setups I've heard embody this philosophy.

Brands like McIntosh and Audio Research (USA), Icon Audio (UK), and Triode (Japan)—along with many boutique manufacturers—continue to champion tube technology.