In this video I compare the two most important mods that were done to Slash Marshall Amps - #34 vs #39. #39 requires an additional tube and actually Slash used #36 which is a copy of #39 on Appetite for Destruction. I'm recording these two through a Marshall 4x12 with 1980s Marshall Vintage Speakers in it. ( Slash most likely used G12-80 on AFD and Greenbacks on UYI). The interesting thing here is whether #34 that doesn't require the addition of an extra pre amp tube provides enough gain!