EL34 Vs 6550 - Power Tube Comparison

Gibson Les Paul 1959 Reissue with Fargen OLDE 800 Mk2 and 1970 Marshall 2x12 Cab Model 1972 with Pre Rola Celestion Greenbacks G12M25 55Hz, T1511. Miked by 2 BeyerDynamic M160 Ribbons, at the grill and 6 feet out pointing up. A Weber Mass 100 Power attenuator is used