Fender Bassman
The Fender Bassman is a series of bass amplifiers introduced by Fender during 1952. Initially intended to amplify bass guitars, musicians used the 5B6 Bassman to amplify other instruments, including electric guitars, harmonicas, and pedal steel guitars. Besides being a popular and important amplifier in its own right, the Bassman also became the foundation on which Marshall and other companies built their high-gain tube amplifiers.
History[edit]
The 5B6 Bassman[edit]
During 1952, the Fender 5B6 Bassman amplifier was introduced as a combo amplifier cabinet that included the amplifier chassis combined with one 15" speaker. The 1952–1954[1] 5B6 Bassman amplifiers had two 6SC7 or 6SL7GT pre-amp tubes, two 5881 power tubes and a single 5U4G rectifier tube. It was designed to generate 26 watts at an 8 ohm impedance load, and offered a cathode-based bias.
From 1952 through the spring of 1954, Fender produced approximately 660 model 5B6 Bassman amplifiers (serial numbers #0001–0660). The earlier cabinets have been called "TV Front" designs,[1] with a front panel that had a rectangular grill cloth with rounded corners and looked much like a television of that era. In 1953 the cabinet designs were changed to the so-called "Wide Panel" design, with a 5 inch wide tweed covered panel above and below a wider swath of grill cloth. Fender ceased production of 5B6 Bassman amplifiers during the spring of 1954.
The 5D6 Bassman with dual rectifiers[edit]
During November 1954, Fender introduced the newly designed 5D6 Bassman amplifier offering four ten inch speakers and was designed utilizing two rectifier tubes. The 5D6 was a major departure from the earlier 5B6 Fender Bassman model. Designed by Freddie Tavares, longtime R&D man at Fender,[2] the new circuit included two rectifier tubes and became known as the Dual Rectifier Bassman.[3][4] Instead of the single 15" speaker, four 10" Jensen Alnico P10R speakers were used. The circuit had two innovations: a fixed bias for the power tubes, which increased power in comparison to the earlier cathode bias design, and a cathodyne phase inverter, using half of the 12AX7 tube and allowing a third gain stage on the other half.[5]
The first 4x10 Bassman amplifiers started with a batch of prototypes in November and December 1954, model 5D6. No schematic for the 5D6 circuit has ever been found, but Ken Fox and Frank Roy have created a few from originals, and copies are freely available online. Only 11 of these early 5D6 Bassman examples are known to have survived. The lowest serial number known to still exist is 0013 (Frank Roy), 0035 (Albert Talley), 0075 (Jim Cornett), 0077 (Perry Tate), 0089 (Mark Grandfield), 0701, 0745 (Walter Horton), 0769 (Hayes Kolb), 0780 (sold on eBay Nov 2006), 0783, and 0785 (Hayes Kolb) are among those still known to exist.
Narrow panel models, 1954 to 1960[edit]
Fender began making other models with tweed covering, a similar open backed cabinet with a rectangular grill cloth and a narrow (just over an inch wide) tweed covered panel at the top and bottom. Produced from 1954 until 1960, these models are called the "narrow panel" tweed amps .[5]
Fender introduced the model 5D6 "DK" in November 1954 followed by the 5E6 Bassman Amp during early 1955. The 5E6-A Bassman model was introduced later that year and included some evolutionary improvements. Demand for the tweed Bassman amp grew, so Fender increased production. By the middle of 1957 more than 1,500 examples of the 5E6 series had been sold.[6]
In July 1957, Fender introduced the model 5F6 Bassman. This model also had four Jensen P10R speakers, but the power supply was redesigned around a single 83 mercury vapor rectifier tube, and a new preamp circuit was introduced that included a three knob tone stack, with separate controls for Treble, Mid and Bass. The power amp included a "long tailed pair" phase inverter, an innovation that noticeably increased the "headroom" or clean power output capability of the amplifier. Similar preamp changes were also incorporated in the 5F8 Twin Amp at about the same time, but not on other large size Fender amps.