#1
i have a fender princeton king and i play a gibson lp deluxe and a fender american deluxe strat and i cant hear any twang whatsover with my amp, but when i play through my other amps or in a music shop the twang is so clear.
#2
so
Gear:
Jackson SL-3 Soloist w/ licensed Floyd Rose
Peavey VK 100 Head
Earcandy Boa 2X12 Cab w/ 70 watt Speakers
Fender Frontman 15 Watt Practice Amp

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#3
you're not gonna get much twang from the Gibson. Try the strat's bridge pickup? Maybe you need new tubes? I dunno.
#6
Could be a tube issue. How old are the tubes in your amp, and at what volume is your amp set to? Or maybe it's a difference of having a bright switch turned on when using other amps that's giving you added twang and no bright switch on for the princeton?
Washburn WI-64
Jackson DK2
Randall RM100C
Digitech RP200A
Digitech DF-7
Digitech Phase Shifter
Boss OS-2
Boss Bf-2