Sovtek 12AX7WA is world-renowned for its smooth, round tone. This ultra-low microphonic tube is used by Fenderﾮ, Ampeg, Carvin, and Hartke, among others. Standard Tested: Tested for all faults and crackles etc but balanced triodes are not guaranteed. Premium Tested: As above but specially selected for V1 or Phase Splitter positions. These have balanced Triodes and low in noise. Factory Tested: Sold as received directly from Sovtek factory - No testing at Hot Rox. General-purpose high-mu low-gain twin triode with ultra-low microphonics, by Sovtek. Replacement for all circuits requiring 12AX7/ECC83 types. • World-renowned for its smooth, round tone. • Used as OEM tube by major manufacturers such as Fender, Ampeg, Carvin, and many others • 7025/ECC83 equivalent Sovtek tubes are quite simply the absolute best. We design and manufacture our tubes, engineered for demanding high fidelity, reliability and overall warmth. Be sure to insist on genuine Sovtek vacuum tubes the next time you retube -- you'll be getting the absolute best possible tubes for any demanding application.