I finally completed my second G*S*G amp, I had started it earlier in the year, and had all the machanical assembly done, and the PC boared "stuffed" leaving only the final wiring to be completed.
It is built on a Hammond 12X10X2 Steel, black powder-coated chassis.
I finally got around to doing that yesterday, and everything came up running perfectly!
The OPTs are a set of "custom" MQ RH-60s, and I replaced the paralleled 180 ohm WW resistors with a second 1.5H choke. Other than that, it is more or less "stock". The "custom" part of the MQ OPTs is that they have end bells and no UL tap on the primary, as opposed to the stock RH-60s which have a UL tap on teh primary, and brass shannel frame mounting.
They look very good mounted on the black PC chassis.
The output tubes are 1958 vintage Russian 6C4C (6S4S) which are the old fashioned twin plate version. These run with 46.5V across the three paralleled 2.74K resistors, or about 50 mA per side, with 305V on the plates. The rectifier is GE 6AX5 and the driver tubem Tung-Sol 6SL7, both NOS / NIB. Interstaeg coupling caps are the green Russian K42y-2 PIO 0.1 uF / 500V "kommie kaps", as they are often called over at Bottlehead.
Sound quality is great, and is improving with more and more runtime.
The tube data sheets enclosed with the 50 year old Russian tubes indicate that they were manufactured at the Leningrad "K-18" tube works, in 1958.
Interestingly enough, these tubes have the "winged C" Svetlana logo, as does the data sheet.
The data sheets also have a form on the back, to be filled in with the date of installation, the date of removal, the number of hours of operation, and the reason for removal.
One thought occured to me - I am sure that the folks who were making these tubes five decades ago had no idea that they would end up in the USA half a century later... From Cold War to "cool sounds"... Yellow_Light_Colorz_PDT_06
/ed B