+1 i had electro harmonix 12AX7 in Fender Pro Junior and replaced em with JJs and it was cleaner (in a good way) and warmer and also chimier just overall better.If you want a more balanced preamp tube, go with JJ tubes.
Seemed too bright and fizzy.
They can be bright on the top. I dig em in a darker amp, might be a bit toppy with that amp. What speaker are you running through?