When you turn on your tube amp, the tube filament at the center of the bottle receives a voltage (usually 6.3V) that heats the cathode to free up electrons in preparation for current flow. Tetrode tubes have four electrodes-the aforementioned cathode and plate, as well as a control grid and screen grid. The power tubes we’re discussing here fall into three categories: tetrode, pentode, and beam power. While all power tubes have a cathode and a plate, much of each model’s sonic character is due to its specific components and construction.

(This is why guitarists across the Atlantic refer to our little glass friends as “valves” rather than “tubes.”) The electrons flow from a part of the tube called the cathode to the tube’s plate, as shown in Figure 1. This diagram of a 6L6GC illustrates the main parts found in the power tubes we’re discussing.Ī power tube is essentially a control valve used to regulate the flow of electrons. Be sure to check out the power-tube comparison video we also created so you can hear the differences between each tube type.įigure 1. Also, players used few, if any, effects in those days, so you can often hear the sound of a guitar plugged directly into an amp, providing clear examples of the core sounds associated with each tube type. But during that era, there was a greater separation between American and British sounds. I don’t mean to suggest that tube amps are only good for playing classic rock. To represent the signature sounds of the most popular tubes, I’ve relied on classic rock examples from the 1950s, ’60s, and ’70s. Getting to know those tonal characteristics can be a huge help, whether you’re trying to track down a new amp with specific sonic traits, or just wondering whether you can change the sound and feel of an amp you own by using different power tubes (see the Swapper’s Delight sidebar).

Regardless of its manufacturer, each power-tube type-E元4, EL84, 6L6, 6V6, 5881, etc.-has a basic sonic personality. The “power tube” name is a bit deceptive, however, because these big bottles don’t just power your speakers-they actually play a significant role in shaping your amp’s sound and responsiveness. Power tubes (aka output tubes) are typically the biggest ones of the bunch, and they provide the last stage of amplification for the guitar signal before it’s delivered to the speakers. Look at the back of any all-tube amp, and you’ll see warmly glowing glass bottles in a variety of shapes and sizes.

Cathode bias guitar amp