Years ago we did a lot of research for tubes that work well for harp players and unlike amps used for guitar, a harp amp likes a phase inverter tube that is NOT balanced. So this kit includes a matched pair of the JJ EL84's, standard ECC81 for V1 and an ECC832 for V2. This gets you more volume before feedback and accentuates the unique harmonics necessary for a great harp sound.