Bassman

Notes for further expansion:

Scraped from: https://www.facebook.com/photo.php?fbid=1827988440586988&set=p.1827988440586988&type=3&theater&ifg=1

During November 1954, Fender introduced the newly designed 5D6 Bassman amplifier offering four ten inch speakers and was designed utilitizing 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, the new circuit included two rectifier tubve and became known as the Dual Rectifier Bassman. Instead of the single 15" speaker, four 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.

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.

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From FB channel: "Tube Amplifier Repair and Diagnosis" https://www.facebook.com/photo.php?fbid=10213182387928017&set=pcb.1873993402675691&type=3&theater&ifg=1

AP: Uhm OK, if you want to count an amp of which only a couple of dozen were ever made, and only eleven are known to exist today. The 5D6 is more of a unicorn than an amp. I am fairly confidant this isn't a 5D6.

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RT3: I own a 5D6-A and a 5E6, why can't it be one of those?

AP: I thought the E6 went back to a single driver. My mistake. You own one of the eleven ~200 5D6-As ever built?

RT3: No, the 5D6 was the 1954 prototype of which only 200 were made. 100 in November of 54 and 100 in December of 54. The 5D6-A was the 1955 model these go up for sale periodically, in fact you can find them on eBay or Gary's vintage guitars for around $10k. The 5E6 is the 1956 model.

AP: My memory was there were about 180 5D6s and abut 200 5D6As. Live and learn.

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There appears to have been several different "Bassman" circuit topologies:

• 5B6

November 1954 through December 1954 (1)

• 5D6 - Only 173 built. Only 11 still exist. Only 4 are still "vintage".

January 1955 - March 1955 (1)

• 5D6A - around 200 built

March 1955 - 1957

• 5E6 - 2x 5U4 Dual Rectifiers

• 5E6A

1957 - 1960 (?)

• 5F6
• 5F6A

(1) http://www.tdpri.com/threads/another-in-a-tweed-series-5d6-bassman.279056/

These all need to be researched and for the information to be posted here...

Jensen P10R

-Zander