The TELEFUNKEN ECC83-TK is a well-balanced tube suited for all types of music and playing styles. Designed to allow for cleaner headroom than higher gain 12AX7s when pushed into overdrive, it offers distortion with strongly defined lows, a rich mid range and clean, smooth highs. 12AX7's are known for their rich even order harmonic distortion when driven into overdrive. Even order harmonics fit into the western musical scale and are more pleasing to the ear than the harsh odd order harmonic distortion created by transistors. The 12AX7 is also known as the ECC83. TELEFUNKEN Elektroakustik will not be held responsible (financially or otherwise) for equipment that is damaged from the use of tubes purchased from us. Each tube has been fully tested to ensure reliability and is guaranteed to perform as described. It is the responsibility of the customer to consult with the equipment manufacturer (or qualified technician) for the selection of proper tubes and proper installation and biasing procedures.