I always thought my RI Marshall 50w and 100w sounded quite different from each other. After all these years I'm actually taking a closer look. The 50w uses a 1k cathode resistor for V2a, no .68 bypass cap. Otherwise pretty normal, has a sticker that says "5881" but came with EL-34. The 100w has an 820/.68 on V1a cathode(!?!), and an 820/330 like you'd expect on V2b. On the 470k mixer resistor for channel 1, a 470p in parallel with a 120p. On V2a, an 820, this time with the .68 bypass cap. At least I know why the 100w seemed to have more headroom--that V1a cathode thing, and the more aggressive mids. Now, was that a goof or were they really copying some great old head that they liked?