Is the sweet spot for your Prescription just a little to loud for you? This is our Low Output Standard Retube Kit for the Dr. Z Prescription ES Heads and Combo Amps. It contains a matched quad of JJ EL844's for power to drop the overall output a couple decibels, a JJ GZ34 rectifier tube, an EF806 for V2 along with two ECC83S's with one being current balanced for the phase inverter in V3.