The MESA® STR-445 is a 6L6 that shares some qualities of a 6CA7 in that it has tight, articulate low-end for excellent bass definition along with beautifully balanced mids and a chiming top-end that cuts without harshness. It’s a great choice for our Rectifier Series to tighten low-end, add top-end cut in a perfect “Rock/Claw” frequency, while avoiding “buzz” or “sizzle” in the upper octave.