GSG converted to 45

[lth1]

Besides the heater voltage and socket, what else needs to be changed in the Get*set*Go to run the 45 tube. I changed a pair of Bottlehead Paramour 1's to the 45 and really like the sound, next shunt regulated SR45 conversion.

Cordially,
Lee Hankins

[EWBrown]

The cathode resistors' value would have to be increased, to accomodate the 45's somewhat more "modest" plate dissipation ratings and max P to K voltage.

I'd aim for between 1500 and 2000 ohms, 10 W for each 45. Other than that, everything else should be good to go... Probably want to keep the
plate current at 30 to 35 mA, in order to to prevent a case of red-plate-itis. They are more delicate than the modern production single plate 2A3s and 6B4Gs, so they need to be treated gently. The higher plate resistance of teh 45 may dictate using a higher impedance OPT primary, as well, at least 5K, vs 2.5 to 3.5 K which is the norm for 2A3s and 6B4Gs.

I haven't yet tried any of this, but I have seen postings over at BH over the years, about converting Paramours from 2A3 to 45 operation. I have one single NOS 45 in my stash, and have been too "cheap" to go find it a mate.

IIRC, the stock (2A3) Paramours use 1K for cathode resistor - I have the newer version PIIs, and can flip one over for a peek under the chassis plate, to verify this.

/ed B

[lth1]

Hi Ed,

coverting the Paramours (1,II) to 45 (not SR45 version) the cathode resistor is increased from 1200 ohms to 1600 ohms.

the power supply resistor increased from 270 to 1600 ohms, or if a choke has replaced the resistor, then a 1300 ohm (1330) plus the choke is used.

the 45 version sounds IMHO alot better than the normal 2A3 Paramour

Lee Hankins

[EWBrown]

I've found that 2A3s and 6B4Gs sound a little bit nicer with a 5K OPT, there is a small loss of maximum output wattage, but this also lowers the THD noticeably, which is always a good trade-off.

I'll have to put my lone 45 to work, just to hear how it sounds, and have a side-by side comparison with the PII and GSG "stock" units.

Then there is always the chance to roll in the old school twin-plate 6B4Gs vs the single plate modern ones for comparison, and set up one channel with each tube type and then play a mono source through them.

The original Svetlana Russian 6B4G copies (6C4C) were of the twin plate design. Look up my comments about "the brick bomber" sometime, for the rest of the story of how the Soviets copied our B29s after WWII, and called them Tupelov TU-4s. The only part that they did not (and could not) duplicate was the landing gear tires.

/ed B