GT-12AY7 tubes pass every Groove Tubes premium certification for micro phonics, hum, physical characteristics and function. Quite simply the best 9-pin triode preamp tubes you can buy - specifically designed and tested for musical instrument amplification and standard equipment on Fender amps. Outstanding and consistent performance for mixing and matching to get a signature tone from your amp. Low-gain tube used in very early Fender amps. Can sub for a 12AX7 to lower gain and produce a slightly warmer tone. Great for harp or blues where softer, more compressed distortion at lower volumes is desired. Medium/soft gain.