12AX7

The 12AX7 tube (also known as the ECC83 in the UK) is the quintessential modern guitar amplification preamp vacuum tube. The 12AX7 is a twin-triode tube, meaning that it has two distinct triodes inside one glass housing. These tubes are known for their high-gain sound, and multiple 12AX7 tubes are often cascaded to build up more and more gain. Generally, clean amps and clean channels of multichannel amps have fewer 12AX7 tubes than the high-gain channels (and amps) do.