Want all the gain you can get and the earlier breakup of the JJ EL844's? This is our Low Output High Gain Option Retube Kit for the Dr. Z Maz 18 Heads and Combo Amps. It contains a matched pair of JJ EL844's for power to drop the overall output a couple decibels, a JJ GZ34 rectifier tube, a standard JJ ECC81 to replace the 12AT7, two handpicked High gain ECC83S's for V1 and V2 along with two JJ ECC83S's with one being current balanced for the phase inverter in V5.