Can anyone tell me what make of tube is used in the F2-b pre amp???

12AX7. We are not loyal to any particular brand. We pick whichever 1) sounds good and 2) fits under the shielding sleeve.  
 
If you're look at NOS tubes, look for 7025, they were the good 12AX7. However, now, all the 12AX7 makers are only making the 7025 version, so the distinction is only valid when looking at the old stuff.

In my older F2B, I use a matched pair of the JJ/Tesla ECC83/12AX7 they are a Telefunken clone..and sound pretty good to me!
 
I also like the new Groove Tube Mullard clone..GT12AX7M. It also sounds good, but I prefer the JJ's.

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