Marshall Lead 12 at 120dB?! \m/

Using the return of the FX Loop and line out jack, I’m playing the Preamp of a 1987 Marshall Lead12 through the Power Amp of a 2015 Marshall 1987X. The Cab is a 1971 Marshall 1982A with stock G12H30 55Hz Celestion Greenbacks with Pulsonic cones. Guitar: 2013 Gibson SG Custom Shop Standard Aged.