12ax7 12at7 12au7 12bh7 12ad7 12ay7 12rll3 12rhh14 / ecc83 ecc82 ecc81. 5star = factory 50-hour aging, plated grids, higher heater current (to avoid burnout), better operator build + inspection. revered for work-horse reliability, best-of quality, and balanced sound reproduction.
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