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The Fender Bassman is a bass amplifier introduced by Fender in 1952. Although it was originally intended for amplifying bass guitars, the Bassman was also used for non-bass electric guitar & pedal steel guitar amplification.
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The Early Fender Bassman Years * Introducing the 5B6 Bassman
During 1952, the Fender Bassman amplifier with circuit design "5B6" was introduced as a combo Amp product with one fifteen inch speaker (1x15). The 1952–1954 Fender "5B6" 1x15 Bassman is a closed back cabinet with two small three-inch rear ports and a single fifteen inch speaker. The amps 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 of power output, an 8 ohm impedance load and offering 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, 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 ended production of the 5B6 Bassman amp during the spring of 1954.
Up until the late 1950s few guitarists were using Bassman amplifiers. However, in the late 1950s used 5B6 Bassman amplifiers with the 1x15 configuration became a favorite of guitar players; however, by that time, model 5B6 had been discontinued for more than 4 years. Leo Fender's partner, George Fullerton, was quoted as saying, "The 5B6 was probably the best guitar amp we ever built."
Fender was preparing to introduce to the world a revolutionary new Bassman amplifier design during November 1954. Fender stopped producing the 5B6 1x15 Bassman during the Spring of 1954. No Bassmans produced for six months between May and October 1954.
The Fender 5D6 Bassman Breakthrough ~ First Dual Rectifier Amplifiers
The design for model 5D6, introduced in late 1954, was a marked departure from the earlier model 5B6. This new design was pioneered by the late Freddie Tavares, longtime R&D man at Fender. "The 4x10 Bassman was essentially Freddie Tavares' design. Leo was working on something else at the time." The new Tavares Fender Bassman circuitry design included two rectifier tubes and became known as the Dual Rectifier Bassman.  |  |  |  Instead of the single 15 inch speaker, four 10 inch Jensen Alnico P10R speakers were used. The circuit was different too, with two innovations that were a breakthrough for Fender, soon to be adopted on other powerful Fender amps of the period: 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.During the 1954 5D6 Bassman production run, Fender installed the Triad 7926 power transformer, Triad 2770 output transformer and the Triad 14560 choke. Along with the dual 5Y3 rectifier tubes and the set of Triad transformers, the 1954 Fender 5D6 Bassman became known as the "Dual Rectifier Bassman". Immediately in 1955, Fender changed the 5D6-A Bassman circuitry from the Triad 7926 power transformer to the Triad 7993 power transformer as well as changing the rectifier circuitry from utilizing dual 5Y3 rectifier tubes to redesigning the Bassman circuitry for dual 5U4 rectifier tubes. The 1954 5D6 Bassmans were the first to use dual rectifier tube circuitry. Fender ended dual rectifier Bassman production in 1957.
Fender produced approximately 83 quantity "5D6 DK” 4x10 Bassman prototypes during November 1954; approximately 89 quantity “5D6 DL” 4x10 Bassman prototypes manufactured during December 1954; and approximately 100(+) 1955 Fender “5D6A EA” 4x10 Bassmans manufactured during the first two months of 1955. These three 5D6 prototypes helped to generate a massive and successful Fender marketing campaign introducing the (now world famous) 1955 Fender 5E6 4x10 Bassman during March of 1955 to the guitar and amplifier world. Therefore, it is to be acknowledged that the first three 1954–1955 "5D6" and "5D6-A" series of prototype Bassmans established a production path for producing Fender’s successful new and unique 4x10 Tweed Bassmans . . . . an amplifier for musicians that would dominate the 1950s popular music scene. As well, the "5D6" Bassmans have a unique sound & tone all their own.
As of February 2013, the earliest documented existing 1954 “5D6” "DK November Bassmans are: #0701 (DK), #0745 (DK), #0769 (DK), #0780 (DK), and #0783 (DK). The second series of 1954 “5D6” "DL" December Bassman serial numbers known to exist are: #0013 (DL), #0033 (DL), #0035 (DK), #0075 (DL), #0077 (DL), and #0089 (DL). These very rare few 1954 “5D6” 4x10 Fender Bassmans are known to sound uniquely different when compared to the later 1950s Fender 4x10 Bassman amplifiers. The Fender 5D6 tone is generated from the uniquely designed amplifier circuits utilizing two rectifier tubes, instead of one rectifier tube circuits or solid-state rectifier circuits Fender designed for Bassmans amplifiers since 1955.
Greg Gagliano's account of serial numbers ranging from 0600 to 0900 is not accurate as there are no known 1954 or 1955 Fender 5D6 4x10 Bassmans with serial numbers in the 0600's, 0800's nor the 0900's. The November 5D6 Bassmans began their serial number run starting with number #0700 through #0783. The 0700 run of serial numbers are a direct extension of the 0600-0660 serial numbers used by Fender's production for the previous Fender 5B6 1x15 Bassmans. November "DK" 1954 was the first of two 1954 Fender 5D6 production runs. The second manufacturing production run for the Fender 4x10 5D6 Bassman ran completely during December "DL" 1954. These "DL" 5D6 Bassman's were serial numbered from #0001 through #0089. Fender used the 0001 to 0089 serial numbers during December to prepare for the 1955 year with serial number "0100" for the 5D6A January 1955 Bassmans (***Note: Approximately 100-200 quantity 1955 5D6A 4x10 Fender Bassmans were produced from January through March 1955. Recently uncovered during February 1955 is a new 1955 5D6A serial number series listing = "EC" for March 1955 with SN#0823. No other "0800(+) series" of serial numbered Fender Narrow Panel Tweed Bassmans are known.
The first 4x10 Bassman amplifiers started with a batch of prototypes in November (DK) 1954 and December (DL) 1954 with prototype model “5D6”. Original Fender schematics for the 1954 "5D6 DK" circuit has never been found. Ken Fox and Frank Roy have created a few “5D6 DL” schematics from original known “5D6 DL” amplifier examples ~ copies are freely available online. The 1954 “5D6 DL” December Bassman schematics can be accessed by links to: 1) http://www.schematicsunlimited.com/?z=fender and 2)http://schems.com/manu/fender/bassman_5d6a.pdf
Authors John Sprung and John Teagle (Fender Amp: The First Fifty Years – 1995) wrote that, "reportedly there is a 5D6 model Bassman". In another very recent book, "The Soul Of Tone - Celebrating 60 Years of Fender Amps" (Tom Wheeler – September 2007, page #170), the author refers how little known the 1954 5D6 Bassman is, quoting Peter Tate (5D6 Bassman owner) as stating that he (Tate) knows the existence of only one other 5D6 Bassman amplifier. Apparently these authors knew of the early 1954 5D6 4x10 Bassman amps but were not aware that Fender actually produced at least 170 5D6's during November and December 1954. The 1954 0700 serial numbered series is a continuation of the 0600 serial numbers used on Fender's 1954 model 5B6 1x15 Bassman amplifiers. Obviously, the 1954 Fender "5D6" 4x10 Bassmans are highly collectable and coveted. Greg Gagliano generated some outstanding Fender amplifier history, published during 1997, but his efforts have been updated since. Greg Gagliano sited in his article that not all Fender amplifier production history is known (at that time in 1957) and that new Fender amp models and variations are uncovered and brought forth every year. Since Greg Gagliano's article, Fender 5B6, 5D6 and 5D6A Bassmans' production dates and serial numbers have been more accurately updated and recorded below.
The Narrow Panel Years * 1955 to 1960
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. The Fender Bassman amp continued to evolve during this period.
Fender produced approximately 83 quantity "5D6 DK” 4x10 Bassman prototypes during November 1954; approximately 89 quantity “5D6 DL” 4x10 Bassman prototypes manufactured during December 1954; and approximately 100(+) 1955 Fender “5D6A EA” 4x10 Bassmans manufactured during the first two months of 1955. These three "Narrow Panel" 5D6 prototypes helped to generate a massive and successful Fender marketing campaign introducing the (now world famous) 1955 Fender 5E6 4x10 Bassman during March of 1955 to the guitar and amplifier world. Therefore, it is to be acknowledged that the first three 1954–1955 "5D6" and "5D6-A" series of "Narrow Panel" prototype Bassmans established a production path for producing Fender’s successful new and unique 4x10 Tweed Bassmans . . . . an amplifier for musicians that would dominate the 1950s popular music scene. As well, the 1954 "5D6" Bassmans have a unique sound & tone all their own.
Fender introduced the model 5E6 Bassman Amp in early 1955, followed later later that year by model 5E6-A to include 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.
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.
In 1958, Fender introduced the model 5F6-A, This final innovation in the Tweed Bassman added a change from the 83 to the GZ34 rectifier tube, as well as a modification in the circuit for the Presence control. In early 1960, Fender began using Jensen P10Q speakers in the model 5F6-A Bassman Amp. With more power handling and clean output, these speakers are considered by many to be an upgrade over the earlier P10Rs, but some players prefer the darker and more expressive sound of the earlier speakers.
Many writers have heralded the 1950s Fender 4x10 Bassman amps as the greatest guitar amp ever. The 5F6-A Bassman circuit design was copied in the JTM-45 designed and produced by Marshall in the 1960s. The 1959 Basssman was successfully re-issued by Fender Musical Instruments Corporation in the 1990s, and has generated demand for Tweed Bassman amps and created a strong market both for the re-issue and the original Bassman amplifiers.
December 1960 was the end of production for Fender Tweed 4x10 Bassmans. During 1961, Fender introduced their unique newly designed “piggy-back” Blonde 6G6 2 ohm 50w Bassman “Amp Head” accompanied with a Blonde 2x12 extension speaker cabinet.
1950s Fender Bassman: Serial Number and Model Number Chart 
Bassman 5B6 (tweed)
0001 to 0300 = 1951
0300 to 0400 = 1952
0400 to 0600 = 1953
0600 to 0670 = January throught May 1954
Bassman 5D6 (tweed)
0700 to 0783 = November 1954
0001 to 0089 = December 1954
Bassman 5D6A (tweed)
0100 to 0200 = January 1955
0823 = March "EC" 1955, recently uncovered February 2013
Bassman 5E6 (tweed)
BM00001 to BM00550 = 1955
Bassman 5E6A (tweed)
BM00550 to BM01200 = 1956
BM01200 to BM01600 = 1957
Bassman 5F6 (tweed)
BM00001 to BM00400 = 1957
Bassman 5F6A (tweed)
BM00400 to BM01500 = 1958
BM01500 to BM03100 = 1959
BM03100 to BM04600 = 1960
The Piggyback Years
During late 1960, Fender introduced a completely redesigned model 6G6 Bassman Amp, using the “piggy-back” design. The distinctive feature of this design is that 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. The 6G6 model was covered in rough Blonde colored Tolex material with Oxblood colored grill cloth. It had a single GZ34 rectifier, two 5881/6L6GC power tubes and four 12AX7 preamp tubes. The output was 50 watts at 8 ohm into a single 12 inch speaker, with a "Tone Ring" baffle in the speaker cabinet. In early 1961, model 6G6-A was introduced with a solid state rectifier replacing the GZ34, and two 12 inch speakers with a conventional baffle in a slightly larger cabinet (wired in parallel) with a 4 ohm output. In 1962, model 6G6-B was introduced, which incorporated circuit changes but used the same speaker configuration. In 1963 smooth Blonde Tolex covering was used instead of the early rough texture cover, and a light tan grill cloth. Later examples of this model used smooth Blonde Tolex covering with a gold weave grill cloth, or a black Tolex covering with black and silver grill cloth and white knobs (the so called "Tuxedo" model).
In 1964 Fender introduced the “Blackface” design, with black tolex covering and a black painted control panel. These models are often referred to as "Pre CBS" Fender amps, because the "Silverface" design was introduced in 1968, following the acquisition of Fender Musical Instument Co. by that Columbia Broadcasting Systems, with circuit changes and other modifications that are considered by many to be a step backwards in quality to reduce the cost of manufacturing. 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.
Legendary Tweed Tone
Despite the fact that the tweed covered Fender Bassman amps were originally marketed for bass guitar amplification, the 4 x 10 design created by Freddie Tavares was meant to be a multipurpose amplifier, with the ability to work as well for guitar and harmonica players as for bass. "The attempt was to make kind of a two edged sword bass amp that other players could use, too, so it could fulfill two roles and make it more acceptable to the buying public."
The tweed 4 x 10 Bassman amps of the 1950s have been used by guitar players since their introduction, and are acknowledged to have a more “raw” sound than did later Bassman models. So many players have used this amp model for performing and recording that much has been written about its "legendary tone." In the words of Billy Gibbons, guitarist for the rock and roll hall of fame band ZZ Top, "When all is said and done, I go back to the house and plug into a 4 x 10 Bassman and just turn it up."
The big innovation began in the late 1950s, when Fender's renowned R&D man Freddie Tavares created a circuit that used a cathode follower in the tone circuit, providing a slight compression of the sound, combined with a cathodyne or "split tail" phase inverter, allowing half of the phase inverter tube to be used as a third gain stage, increasing current in the signal sent to the power amp. This design increased the amp's dynamic output range making it a favorite of guitar players everywhere. This preamp circuit design was adopted for use in other powerful Fender amps of the narrow panel period which are also very popular with guitarists: the model 5E7 Bandmaster, 5E5-A Pro Amp, 5F4 Super Amp and the 5E8-A Twin Amp.
Appropriately, when Fender recently reissued the 1959 (5F6-A) 4x10 Bassman model in 1990, that reissued Bassman was re-categorized as a “guitar amplifier” rather than a “bass guitar amplifier”.
In 1990 Fender began producing a reissue of the 1959 Bassman model 5F6A, known as the '59 Bassman. The newest version of this reissue is the '59 Bassman LTD. The LTD version has a lacquered tweed covering and 4x10 inch Jensen speakers instead of the Eminence speakers used in the earlier '59 Bassman reissue series. David Gilmour from Pink Floyd used a pair of the 1959 reissue to achieve his sound in the studio.
In 2009, Fender introduced the latest reincarnation of the original late '50s Tweed Bassman amp, the Bassman TV series, which includes four sub-models such as the TV 10, TV Duo 10, TV 12 and TV 15. Each of these four amplifiers came with 10", 2 x 10", 12" or 15" speakers, 150 or 350W RMS (depending on the model). Other features include an XLR output, Master Volume, Gain and a three-band EQ with Treble, Middle, Bass, as well as "deep" and "bright" switches which boost the low and high frequencies.
Many famous amplifier manufacturers, including Marshall and Traynor, based their first batch of amplifiers upon the 5F6A Bassman, in examples such as Marshall's JTM45 (a clone of Bassman, using British-equivalent parts), and Traynor's YBA-1 (head form of Bassman).
- Super Bassman (1969–1971) - one speaker cabinet
- Super Bassman II (1969–1972) - two speaker cabinets
- Bassman 10 (1972–1982) - Silverface combo - four 10" speakers, 50 Watts/RMS (models produced after 1977 came with a three-band EQ on the Bass channel and 75 Watts/RMS with ultra-linear output section).
- Bassman 50 (1972–1977) - Silverface piggyback head - two 15" speakers, 50 Watts/RMS - Same specs as the original silverface Bassman heads produced between 1968 and 1972, except for the addition of a tailless amp decal and an AC568 circuit.
- Bassman 100 (1972–1977) - Silverface piggyback head - four 12" speakers, 100 Watts/RMS, became the Bassman 135 in 1978.
- Bassman 70 (1977–1983) - Silverface piggyback head - Same as the Bassman 50, with 70 Watts/RMS and a master volume control.
- Bassman 20 (1982–1983) - Blackface combo - one 15" speaker
- "Fender Wide Panel Tweed Bassman". Ampwares.
- Gagliano, Greg (April 2010). "Dating Fender Amps by Serial Number, Part VI". Vintage Guitar Magazine: 38–39, 100–101.
- Wheeler 2007, p. 164.
- Ware, Mark. "Fender Amp Field Guide".
- "UNCOVERED: Fender 5D6-A with New Serial Number Series". The Amp Garage.
- Kuehnel, Richard (2009). Circuit Analysis of a Legendary Tube Amplifier The Fender Bassman 5F6-A. Pentode Press. pp. 12–15. ISBN 0976982250.
- Wheeler 2007, p. 168.
- Tolinski, Brad (September 1994). "Welcome to the Machines". Guitar World. Retrieved 2011-07-29.