ruffrecords said:I ran your first stage through LTspice. Stage gain is 29dB as is. With the 20dB from the transformer that's a total of 49dB before the first pot. Fortunately tubes can take a lot of level before they fall apart. I simulated yours with 0dBu on the grid and its +29dBu output has about 1% distortion at 1KHz which is a bit of tube tone but not noticeably nasty. This means you should be able to input -20dBu before things start to get into serious distortion.
Acknowledging the later comment about the 10K pot dragging it down, it's useful to point out that this sort of -20 max in is the usual ballpark for vintage tube preamps with 20+ dB gain in the transformer. 49 dB before a gain control is always a problem in modern times with anything hot in output.
Back to the pot, tons of vintage tube interstage gain controls in the 100K-250K range with no treble loss, none I know of with a CF as you are doing.