Replacement Power Tubes for Your Ampeg SVT Need replacement power tubes for your Ampeg SVT bass amp? These are the ones you want. These reliable Sovtek 6550s produce a subtle midrange bump, along with tight bass and excellent top-end extension. At Sweetwater, we give these tubes our highest recommendation — they sound great!Sovtek 6550WE Power Tubes Features: Tailor-made for Ampeg SVT bass amps Produce a subtle midrange bump, tight bass, and excellent top-end extension Matched sextet.