Looking to warm up your 20H or 20HV? This is our Standard Retube Kit for the Jet City 20H and 20HV Amps. It uses three ECC83S's with one being current balanced for the phase inverter in V3. The default power tubes are a matched pair of the JJ EL84's but you can configure this kit to use the JJ EL844's to drop the power output a couple decibels by clicking on the "Customize" button!