Tweed Fender Champ Preamp Tube – 12AX7
The 1959 tweed Fender Champ is a 5 watt single ended Class A amplifier. That means that it has one preamp tube, the 12AX7. The 12AX7 is a miniature dual triode vacuum tube with high voltage gain. You can read all about it in pretty good detail on Wikipedia. After removing the upper back panel, it is all the way to the right as you face the electronics. There are no clear markings on this particular tube to indicate who manufactured it.