Friday, February 4, 2011

The Gibson Amp attack from 1947

Three Gibby amps at once


Here is one of three Gibson BR-1 amps from the same owner, who loves the sound of this model for his style of blues playing, so he got two more for spares.

Rebuilding all three as they all had bad caps and damage from shipping and previous fools playing around turned into a real adventure








This is the first one, above, with a new custom cabinet, amp finished.

The caps are all underneath the turret board so I had to used several tools to cut the leads and fish them out.  There were 22 dead caps per amp as the 60 years is a bit too long, although the sellers on ebay sold these pretty high






This is a very early amp, about 1947, and it has 25 watts, lots of wires, two "metal" tubes, a small glass tube,  three big glass ones, and a very heavy field-coil speaker. 
One of the amps came packed very badly, with the wood magnet brace missing, and the speaker pulled the entire baffle board off.

This amp has a 6sj7 early pentode preamp tube, very close in specs to a EF86, and one of the best preamp tubes, a 6sc7, used for  EQ and line input , a very good sounding tube, and a 6sn7 driver. Two veteran 6L6G tubes in push pull provide 25 watts to the massive 12" speaker








The 6j7, the 6sj7, earlier 39/44 pentodes were great tubes and I have used them in Vintage mike preamps I have built, finding the 39/44 to be one of the quietest preamp tubes ever.






Here is amp two, with the baffle repaired and now held with brass screws through the front, and a with a "notch" cut into the top so the 5u4 would clear because the previous owner could not figure out how to get the chassis out without hitting cabinet with the the tall glass 5u4 and 6L6 "G" "Coke Bottle" shape tubes!
This is a good sounding amp, but typical of early amps, a cabinet disaster.
This is number three, with a original aluminum baffle screen. 






Amp number three, I thought would be a pretty easy job as I knew the amp by now and knew what to do, I thought, until I discovered the previous had "Re-wired" the controls and more in a vague attempt to make some kind of new amp.
I was a lot of work  figuring it out and lots of solder work to get all these early heavy wires all with the same brown color back where they were!
These three amps were restored over four months, the last one in October.
Two brothers made amps for Gibson back then and made some really wild amps, one that had six output tubes and almost 50 watts of power


This link will take you to videos on youtube that show early Gibson amp


http://youtu.be/YuJpfNzrOkI


Info from www.ehow.com

http://www.ehow.com/about_5437499_history-vintage-gibson-amplifiers.html

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