how do I get tubes for my amp? in Amps Posted July 13, 2009 - replace them by a pro, if im right those need to be biased. - you can buy the tubes anywhere local music stores probably sell them, but you can get them at many online stores too. - that sounds like a tube problem, and since its old and since the power-tubes arent as bright, that seems like the likely cause. - as for the age, im sure that silverfaces are in the 70's but im not sure. i bet someone else on here can help you better with that. sorry not too much help, hopefully someone else can add on, but gave you whatever info i can offer.