Tube Mic Pre-Amp circuit electronic.
The 12VAC needed for pin 5 of the 12AX7 can be obtained from point G while pin 4 should be connected to point A.
There are two options for line level signals. First if you know that you”ll be using line level signals all the time with the TMP then you can change the two 33k 1% resistors to 1k 1% types and your done. Alternatively if you want the option of line level or low level signals then you can sacrifice the polarity switch and and rewire it here as shown. Notice that the 47k resistors are again of the 1% variety.
