Want a little cleaner front end and the earlier breakup of the JJ EL844? This is our Low Output SRV Option Retube Kit for the VOX AC30HW Heads and Combo Amps. This kit uses a JJ 5751 for V1 which is in-between an ECC81 and an ECC83S in gain, three standard ECC83S for V2 thru V4, a balanced ECC83S for V5, a JJ GZ34 rectifier tube and a matched quad of the low output JJ EL844's for the power section.