The Sovtek 12AX7WB has more gain and saturation than the 12AXWA version. Its warmer, darker sound is preferred by Rivera, VHT, Demeter, and Kendrick, among other leading amp manufacturers. It can effortless replace the ECC83. We have fully tested each valve for you and give a 180 day warranty. It is a useful valve for calming down amps that sound overly bright..