Want the smoothest richest tone possible from your DSL 401 but you also want the earlier breakup of the EL844's? This kit contains a matched quad of JJ EL844's to drop the overall output a couple decibels for the power section. Three standard Gold Pin ECC83S's for V1 thru V3 and a balanced Gold Pin ECC83S for the phase inverter in V4. A smooth rich tone and an earlier breakup from the power tubes.