Mooer Tube Engine 20W Electric Guitar Amplifier. The Mooer Tube Engine 20W is a 20-watt Class A/B electric guitar tube amplifier. It is equipped with 1 12AX7 (ECC83) valve, 1 12AT7 valve (ECC81), 2 EL84 (6BQ5) valves, Master, Presence, Hi/Low
Gain Input controls.