Seeker of Rock
The One and Only
Many of the hard rock and metal sounds from the 70's and early 80's came from those amps, but they also boosted the front end with something. Even into the 80's with the famous JCM800, those hair metal guys boosted the shit out of their front ends with something. 800's don't have that much gain. Hell, even Angus boosted the front of his JTM45 with his wireless unit.
That's one of the things I like about my particular 900 model and why I was drawn to it. In it's natural state it's like a hot rodded 800 - it even shares the same circuitry and gain structure as the two channel 800's - but with an added secondary gain control if I need more. No pedals necessary, unless I want to, and with the right guitar it will do a pretty chimy clean all the way to Slayer metal. So far I haven't needed that second gain for anything, but you never know when I'll wanna let my hair down and put some spandex on.
The 100w is not appreciably louder than the 50w was, but the percussive punch that comes from the 100w is considerably more substantial than the 50w. You can literally feel the power in the room.
Some good knowledge you're sharing here. Not bad for a kickass drummer turned guitar player. A couple of things I'll add:
The JCM800 Marshall you are likely referring to are older amps...2203 (100watt) and 2204(50 watt) and I think it is called 1987 (Superlead). Those are '70s designs that were basically rolled over with new cosmetics and part of the new JCM800 line. The JMC800 series also produced the dual channel amp 2205 trying to meet the needs of more gain, new combos and iirc even some solid state little models. Oh yeah, and the MOSFET (that a friend of mine owned...blah). To me, and this is highly subjective, most of those amps including the 2205 sound different than my 2204. I almost bought one because your favorite band Felony (Lol, I know) required a gain boost in our tunes, so I was auditioning the single channel 900 thinking it would be the same as my amp but more gain and couldn't quite get the sound. I don't know this as a fact, but I would call it a different amp.
Volume: Some of the stages I have played on were theater sized so I always had room at sound check to fuck around with volumes especially being wireless and able to get far away and listen. I have the 6550 power tube version of the 2204 (American version back then) and from about 5, maybe 6 master volume on, there was no real audible (to my ears) difference in db, just in saturation. The difference between 1 and and say 5 was immense, though.
As you said, I ended up driving my front end with a boost but thank God didn't go through with a mod.