Imagine the surprise when Thomas Edison, tinkering with his light bulb, discovered a mysterious current flowing between the heated filament and a nearby plate. This “Edison effect” sparked a revolution, leading to the birth of the vacuum tube in 1904. Initially a simple “diode,” with no grid, tubes evolved rapidly, with the iconic grid triode emerging in 1907. Think of tubes as a valve, with a heated cathode emitting electrons “boiling off” like water, attracted by a positive anode. But the real magic lies in the grid, a mesh gate that sits between the cathode and anode which controls the electron flow like a dimmer switch, allowing us to amplify or shape incoming signals. Without this grid, tube amplification would not exist.

This basic principle, akin to water pressure regulated by a valve, underlies all tubes. Later innovations like the pentode added more grids for even finer control, paving the way for complex audio applications. Though transistors later took center stage, tubes never truly faded, their unique sonic warmth and dynamic response endearing them to musicians who crave soul over sterile perfection.

By understanding this electron dance within the glass envelope, we unlock the key to harnessing the sonic power of tubes, transforming them from historical relics into tools for crafting your own musical signature.

At Fuzz Audio, we refuse to nitpick tonal characteristics and manufacturing quality when the first issue we have with modern valves has to do with the factory locations. Russia and China are the only countries producing large quantities of tubes these days, and these countries  are not known for protecting the rights of workers, to say the least.

When the vacuum tube was invented, the manufacture of tubes involved the leading technologies of the time. It allowed radio and other electronics to flourish, and all of major electronics brands, around the world, competed to create the quietist, most powerful, most accessible, and smallest vacuum tubes. Factories employed top engineers and scientists to not only invent glorious valves but also to oversee the manufacturing process to ensure quality was achieved. Check out this video from 1948 explaining the “Bottle of Magic” by Western Electric:

There are four tubes in the LA-2A, but only two of those tubes, the 12BH7 and one of two 12AX7s, directly influence the quality of the audio signal. Most of the tonal quality in your unit is attributed to one 12AX7. This means that when deciding on which tubes to upgrade in your amplifier, most of your budget should be directed towards one premium long plate 12AX7.

In 1958 leading into 1959, Jim Lawrence, the inventor of the LA-2A and founder of Teletronix, developed and produced the first LA-1 leveling amplifier, which contained RCA black plate preamp tubes. During the next five years, many things changed in design from the LA-1 to the LA-2A, but the choice of preamp tubes did not. For that reason, RCA black plate 12AX7’s are a must try for any serious user as they are the original stock option and were preferred by Lawrence and Teletronix.

Among the most important tonal qualities audiophiles chase, warmth is an essential element of a rich, full, and complex sound. If you would like to add more warmth to your stereo setup we recommend premium low noise American-made vacuum tubes such as Raytheon black plate 12AX7’s and 12AU7’s or RCA 6L6GC black plates.