Tung-Sol Tube Upgrade Kit For Marshall JCM 2000 DSL 50 DSL 40C Amps EL34B/12AX7 This set includes (2) Matched Tung-Sol EL34B power tubes (3) Tung-Sol 12AX7 preamp tubes (1) "Gain Balanced" Tung-Sol 12AX7 preamp tube (phase inverter) marked with yellow "Balanced Triodes" Sticker