A Gibson GA20T ... in the house at JuanzAmpz: In the smaller of the Gibson tweed cabinets. Bought from our friend Michael's Music in an eBay auction for about half of his former asking price ... deflation ... 12" replacement Qunicy alnico speaker, twin 6V6s, 5Y3 rectifier, and a Strange Brew of preamp tubes including a 6SQ7 and a 5879.
GA20T Schematic here and below with the differences between the GA20 and GA40 as shown:
The 5879 is a pentode, more like an output tube than the twin-triode 12A_7 family widely used in preamps, making its way into boutique amps like Fungus' Winfield Cyclone. Our BBer Mad Dog had nice things to say about the GA40 Here If I get half of that ' ... dark, hot sound, swirly and alive' thing, that'll be fine. Except for the 5879, all the preamp tubes still have their Gibson painted logos pretty much intact. Tremolo controlled by switch in mahogany box. Cleaned up, they come back as:
Fires up, passes a clean signal, lacking some volume, but that channel 2 ... that one has tone written all over it. 8)
GA20T Schematic here and below with the differences between the GA20 and GA40 as shown:
The 5879 is a pentode, more like an output tube than the twin-triode 12A_7 family widely used in preamps, making its way into boutique amps like Fungus' Winfield Cyclone. Our BBer Mad Dog had nice things to say about the GA40 Here If I get half of that ' ... dark, hot sound, swirly and alive' thing, that'll be fine. Except for the 5879, all the preamp tubes still have their Gibson painted logos pretty much intact. Tremolo controlled by switch in mahogany box. Cleaned up, they come back as:
Fires up, passes a clean signal, lacking some volume, but that channel 2 ... that one has tone written all over it. 8)