One of the Greatest: '58 Fender Tweed Champ

This amp covered in luggage-style tweed is considered the cornerstone of all tube guitar amplifiers. First produced in 1953 for beginners, most of them were instead purchased by lap steel guitarists for either country or Hawaiian music. But the fact that they were cheap made them also attractive to young rock and rollers.
The Champ provided great distortion at a relatively low volume level, which suited the mikes and studios of the 50s and 60s..
Technically speaking, the Champ couldn't be simpler. One 12AX7 dual-triode tube acts as the first gain stage and also as the output driver to a single 6v6 output tube, which put out a 3.5 watts (!) RMS inot a 4 ohm load. This was the simplest example of how to use a tube from the RCA tube applications manual, a classic reference book supplied to amp manufacturers in the 40s and 50s. If you are one of those lucky people who have managed to get your hands on the Champ amplifier, do you need to change your 6v6 tubes every few years if you use it regularly. The 12AX7 shouldn't need replacement if its a good one.
If you have bought a Champ Fender from Ebay or Craigslist and you are disappointed with the quality, check to see if the speaker is a true 4 ohm model. Blown Champ speakers are often replaced with a more common 8 ohm speaker, resulting in a big loss of power and tone. Looking for more power and tighter sound? Try replacing the 5Y3 with a solid state rectifier. But stay with a tube rectifier for sweeter distortion.