Elbowgeek
Active Member
I'm going through the phono preamp circuitry of an old Olson tube receiver. It seems that before hitting the grid on pin 7 of the 12AX7, the signal passes through a 47K resistor.
I had noticed that the gain was rather lower than I would have expected and was wondering if this resistor had anything to do with it. Other amps I've got schematics for don't generally have a resistor of any kind betwixt input plug and grid, so could this be attenuating the signal? And would removing it make a huge difference?
BTW, this is an interesting amp. It uses one half of each 12AX7 as phono preamp and the other half as line preamp, obviously to save a bit of money. And 6BM8's on the output. But a very clean unit overall. The sound through speakers is not great, but I believe the phono section has promise, and if I can use it as a phono preamp that would be great.
Thanks for any help
D
I had noticed that the gain was rather lower than I would have expected and was wondering if this resistor had anything to do with it. Other amps I've got schematics for don't generally have a resistor of any kind betwixt input plug and grid, so could this be attenuating the signal? And would removing it make a huge difference?
BTW, this is an interesting amp. It uses one half of each 12AX7 as phono preamp and the other half as line preamp, obviously to save a bit of money. And 6BM8's on the output. But a very clean unit overall. The sound through speakers is not great, but I believe the phono section has promise, and if I can use it as a phono preamp that would be great.
Thanks for any help
D