Marshall's JMP 2203 (and its 1981+ JCM800 cosmetic-rebadge) is the canonical master-volume 100W Marshall, but the chassis has a defining mid-life architectural change that's important for both Jose-mod historical context and for understanding what counts as "stock 2203."
Pre-1977 master-volume 100W (JMP 2203): - Front end uses a parallel-cathode V2a with bypass cap — essentially "a Super Lead front end with a post-tone-stack master volume." - Same gain structure as the four-input Super Lead, just with the master volume added downstream.
Post-1977 JMP 2203 (then 1981+ JCM800 2203): - Front end is rebuilt around a 10kΩ unbypassed cathode on V2a — the famous "cold clipper" that defines the JCM800 character. - This is the canonical 2203 architecture for the JCM800 era.
Per Dave Friedman ([Panel #8 13:39, 15:19]): *"[Pre-77 master-volume 100s are essentially a] super lead front end with a normal post-tone master… they didn't yet change to the 10k."*
Why the cold-clipper sits without a grid stopper: an architectural detail per Shea Monomyth ([Panel #8 29:35]): *"as soon as you get that 10k lower, the fact that you don't have a grid stopper on the second stage means the grid starts just completely going into cut off as soon as you hit a heavy power cord… almost like a gate effect."*
This is the exact problem that Jose's Tier-2 jose-grid-stopper-5k6 mod solves — adding a 5.6kΩ grid stopper before V2a softens the cut-off behavior and smooths the upper-mid spit on hard pick attack. The Jose mod and the JCM800 stock architecture are talking to each other across chassis years.
Naming and chassis identity: Per Friedman ([Panel #8 13:39]): *"a JMP 100 master volume 100 2203 is the same thing as a JCM800. It's the same exact amp. Don't get the idea that it's something different."* The 1981 cosmetic rebadge from JMP to JCM800 changed the front-panel typography and back-panel logo, not the circuit.
Implication for JMIL: when the lab discusses "stock 2203" as the baseline for the cascade-v1-v2 mod, it's the post-77 10kΩ cold-clipper version. Pre-77 master-volume 100W chassis are tonally closer to a Super Lead-with-master than to a JCM800; the cascade-v1-v2 mod has different effect on each. JMIL models the post-77 baseline.