Stevie Ray Vaughan 's favourite, he used it as a replacement for the 12AX7 in V1 of the preamp, to give his overly bright Fender amps a warmer and stronger mid focus.

It just sounds very musical in any tube amp, really so much better then the new stuff.

This tube has a triple mica construction, black plates and a D getter. It was made in the mid 1950's. Holy grail level according to many.

It tested NOS on the Hickok at the FAD Amps workshop in Belgium. It also tested silent and non-microphonic in the V1 position of a guitar amp turned up loud.