Tested under extreme listening conditions and guaranteed to be free of excess noise and microphonic ring.

The Groove Tubes GT-12AT7 preamp tube is manufactured to the highest quality JAN spec. NOS, made in Russia for extremely long life. Used widely in most U.S.-made amps and, in particular, Fender amps. Fender amps with reverb use 2 - 12AT7s -- one for the reverb drive stage, and one as a phase inverter to drive the push/pull output stage. The makeup of the 12AT7 is very similar to the 12AX7 and it can be substituted for a 12AX7 in a pinch. Some players prefer the 12AT7 in the driver stage of a Marshall for a cleaner, brighter tone. (The driver or phase inverter is the 12AX7 located nearest the power tubes.) The 12AT7 is rarely used in a tone-generating stage, but rather in function stages, so the Groove Tubes GT-12AT7 is selected for durability. Country of origin: Russia