Replace the stock tubes in a TubeMeister18 with a set of Electro Harmonix 12AX7 and Mullard EL84. Have only place about 10 hours on them so far but WOW. Great combo, usually use Sovtek in my tube gear and took a chance. So happy I did, got rid of the shrill of the china tubes. The clean is beautiful and mellow, the distortion boost channel...could not ask for easier and better, no need for a pedal. Found my perfect sound with these.