Years ago we did a lot of research into tubes that work well for harp players. What we found is that 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, a standard ECC83S for V2 and an ECC832 for V3. This gets you more volume before feedback and accentuates the unique harmonics necessary for a great harp sound. Just let us know in the comments section if you’re looking for max headroom, moderate or an early breakup so we can select a proper grade for the power tubes.