Leo Fender began building guitar amps before he started manufacturing guitars.
The first of these amps were the K&F models, which were produced between 19.
Fender later on constructed them with "narrow panel", in which all the panels have more or less the same width.
Toward the end, despite keeping such construction, Fender utilized tolex to cover its amps. The blonde amps included all of the piggyback Fender amps (the Tremolux, Bassman, Showman, and Bandmaster) and a few of the combo amps, including the Twin amp.
They were made by the K&F Manufacturing Corporation, which was run by Leo Fender and Doc Kauffman.
Most of the amps were finished in a "gray crinkle" finish.
They included the Model 26 Deluxe, the Princeton, and the Professional.
Fender amplifiers began making a name for themselves with the Tweed series, so called because of their cloth covering, which is actually varnished cotton twill (tweed is a coarse woollen fabric, commonly used for jackets, coats and caps; it is often woven in a twill pattern, which is likely the reason for the confusion over naming.) They were produced for more than a decade and are now eminently collectible and praised for their sound quality.
The first kind used was an off-white fabric, followed by a horizontal-stripe two-tone pattern, and finally a two-tone twill.
At the beginning of the "tweed" era, Fender constructed many of its cabinets in "TV front" style, changing around 1950 predominantly to the"wide panel", where the top and bottom panel is wider than the side.
The original Fender amps were tube-powered and the company also started producing solid-state models in the late 1960s.
The K&F amplifiers were the first "Fender" amps made.
Some of them also came with a dark maroon or "oxblood" grillcloth.