Express preamp voltages?

[Phil_S]

I searched but didn't find much on pre-amp voltages. I'm just wondering how mine compare and if the numbers are in the "relevant range".

B+3 303
B+4 287
B+5 273

V1A, Va=193, Vk=1.19
V1B, Va=213, Vk=1.61
V2A, Va=251. Vk=3.34
V3A, Va=197, Vk=11.71, Vg=8.39
V3B, Va=203, Vk=11.71, Vg=8.48

I understand that the two sections of V1 won't be identical, but I'm not understanding what accounts for the 20v spread. Both feed from B+5 to 100K plate load resistor.

I'd appreciate some feedback on both the question and the general voltage readings. Thanks.

Phil

[rhinson]

preamp tubes are cathode biased in guitar amps (for the most part). if you have 2 of the same value plate resistors getting the same b+ voltage then the difference in the cathode resistor values is what causes the tube sections to draw more/less current and cause the plate voltage to be higher/lower. the same sort of thing applies when cathode biasing power sections as well---smaller value resistor equals lower plate voltage and more current draw, and larger value resistor equals less current draw and a higher plate voltage.
rh

[Phil_S]

<d'oh> of course. I wasn't thinking about it; V1A Rk=1k5 and V1B Rk=2k7. It all makes sense now. Thanks.