Fender Bassman
[citation needed] From 1952 through the spring of 1954, Fender produced approximately 660 model 5B6 Bassman amplifiers (serial numbers #0001–0660).
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.
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.
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.
[citation needed] Demand for the tweed Bassman amp grew, so Fender increased production.
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, midrange and bass.
The 5F6-A Bassman's design is greatly influential in terms of guitar amplication, as the schematic was directly copied by other manufacturers.
The first series of the reissue were made at the Corona, California facility, and came equipped with four Eminence-made 10" blue frame AlNiCo speakers, and a solid-state rectifier unit.
In late 1960, Fender introduced a completely redesigned model 6G6 Bassman Amp, using the "piggy-back" design, in which the amplifier chassis is housed in a small cabinet, attached by metal clips to a larger separate speaker enclosure.
The early models were called "Brownface" because of the dark brown color used on the control panel.
In early 1961, model 6G6-A was introduced with a solid state rectifier replacing the GZ34, and two 12" speakers with a conventional baffle in a slightly larger cabinet (wired in parallel) with a 4-ohm output.
[10] Early "Drip-Edge" Silverface Bassmans made in mid 1967 used the same AB165 circuitry as the previous Blackface versions.
The Brownface, Blackface, and Silverface "piggyback head" (except the Bassman 10 and 20, which were also combo amplifiers) versions of the 1960s, 1970s, and early 1980s generally followed a trend toward cleaner sound and more headroom.
