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GA-25.5

#1 User is offline   dkevin 

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Posted 31 August 2016 - 07:36 PM

I have an amp that seems to be a "tweener". It is labelled a GA-30 but it only has 2 knobs on the control panel and the tone expander circuit slide switch is located below and between the knobs. I refer to it as my "GA-25.5" amp. I bought it as a chassis only. When I was sketching out the layout, I discovered that it differed from most other GA-30's. The preamp tube is a 6SJ7 and there is only one preamp tube like a 25. I was fortunate to find one other person who owned a similar amp. I have heard lots of opinions about Gibson's quality control and that's not really why I am posting. I guess that Gibson was trying to use up overstocked GA-25's and issue the new model (GA-30) at the same time. All in all, I feel fortunate to have one of these rarities.[attachment=21799:GA 30 back.jpg]
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#2 User is offline   badbluesplayer 

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Posted 05 September 2016 - 09:51 AM

Pretty cool! [thumbup] [thumbup]
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TENNESSEE AMPLIFIER COMPANY
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#3 User is offline   dkevin 

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Posted 06 September 2016 - 01:21 PM

The tube lineup is 6SJ7 preamp
6SQ7 PI
6SQ7 PI
6V6 output
6V6 output
5Y3 rectifier
I am attaching a GA-25 and a GA-30 schematic...This amp is like a single channel GA-30 with one volume and one tone control. One of these days I am gonna build a replica cabinet and crank it![attachment=21833:Gibson_GA-25.pdf]
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