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Old June 29th, 2009, 09:06 PM   #5 (permalink)
mojo2001
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Join Date: Feb 2008
Location: Colonial Virginia
Age: 50
Posts: 599
I have had bad experiences with mid 60s Gibsons, in the way you describe.

First, if it has the stock CTS speaker in it, these are some of the nastiest, most mechanical and thin sounding speakers you will ever find. Try a nice fat Eminence, as suggested above.

But that most likely will not be enough.

That amp is so simple there isn't much to blame. Usually the tonestacks are dubious in this era Gibbys, but you don't have one.

I's suggest swapping out the "250pf" cap between the 6EU7 and the 6C5 with a .01--or to make it easy, just wire a .01 in parallel.

Actually it can't be "250 pf" as indicated on the schematic because that would give you a corner frequency of 1100hz...must be 2500pf or .0025, which would be -3dB @ 111hz.

Still cutting it short. Put in a .01 If you need one, I'll send it to ya.

Furthermore, Gibson amps seldom match the published schematic, so who knows what you got.

I tried a few and now won't waste my time on any post 1962 Gibsons. The Kalamazoo Model 2 aka 1965 vintage GA-5 being the only exception.
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