Any Fender Prosonic owners have some recommendations for preamp tubes (especially V1 I am guessing) to get a little less brittleness out of the amp? I run mine currently (have tried other settings too) in "class A" mode, with 2 x 12" 8 ohm out. The OD goes from brittle (but it is ALMOST where I want it to be...just can't get that last 15%) to muffled no matter how carefully or how many permutations I do with EQ and gain 1 and gain 2. It's frustrating, I keep feeling like "there....wait, not quite" and am thinking maybe a change of preamp tubes could get me in a better place. Mine is the head version, no reverb. Thanks for any tips!