Comparison - JCM800 VS JCM900. Marshall 2203 vs 4100. All knobs on full but bass that's about 40%, and for some riffs preamp 50%. B-channel on JCM900. Guitar tone and volume used to shape the different sounds. 2008 Gibson Les Paul 1959 Standard Reissue, 1971 Marshall 1982A with G12H-30 55Hz Pulsonic Celestion Greenbacks. Close mic Unidyne 548, room mic AKG C414BXLII omni at 10 feet. Hotplate attenuation -8db to be able to use only one cab, no EQ compensation on the Hotplate.