The jose-mv-dual-gang mod ships on both platforms in JMIL — it's toggleable whether you've picked the 1959 (Plexi) or the 2203 (JCM800) chassis. But the historical documentation behind the dual-gang switchable pre/post topology is NOT equally strong on both. This entry lays out the asymmetry honestly so builders can match the recipe to their authenticity target.
1959 / Plexi-family (4-input chassis) — strong documentation
The canonical period example is John Sykes's main amp: a 100W JMP (4-input 100W Plexi-class chassis) that Friedman recalled with the shorthand "1A1" — note that "1A1" is Friedman bench-shorthand and does not appear in standard Marshall chassis-code references, so treat the chassis-code label cautiously while accepting the underlying topology — with the dual-gang push-pull pre/post tone-stack MV and diodes wired in. Per Dave Friedman (Headfirst Amps Amp Panel QA, April 2025), Friedman serviced this amp directly and recalls both the push-pull pre/post pot wiring and the diode clipper engaged in both positions. See sykes-1987 for the full Sykes account. The 4-input Plexi chassis (1959 100W, 1987 50W) is the platform on which the Jose modder-school originally established its work in the late-70s LA scene; most of the well-documented period Jose-school amps (EVH #12301, Mars's '73 SL, DeMartini, Sykes) are on this platform.
2203 / JCM800 — thinner direct documentation
JMIL's knowledge entries don't cite a specific Marshall 2203 donor with the dual-gang switchable pre/post wiring. The 2203's stock chassis already has a factory post-tone-stack MV, so a typical Jose 2203 mod just RELOCATES the MV to pre-TS (single-gang) and leaves the factory post-TS MV either bypassed or removed. George Lynch (lynch-jcm800-jose) ran multiple Jose-modded 2203s but the public record doesn't attribute the dual-gang variant to his rig specifically. The 2203 was introduced in 1981, post-dating the late-70s peak of the original Jose customer book; documented Jose-school 2203 work skews toward single-gang Jose MV rather than the dual-gang switchable.
Why JMIL still allows the toggle on 2203
Three reasons, ordered by load-bearingness:
1. The mod is technically implementable on a 2203 chassis. It's a part substitution (dual-gang push-pull pot) + a DPDT switch wiring, neither of which depend on chassis-specific topology. Jose worked on 2203s; a builder following the Sykes pattern on a 2203 produces a topologically valid Jose-school 2203 build.
2. Friedman's modern "Jose" production amp generalizes the topology. Per Friedman (Headfirst Amps Panel #1, Feb 2025): *"We built a fully loaded two-channel Jose with two master volumes, switchable that does not bleed."* The production "Jose" is built on Friedman's own chassis (not a Marshall donor), so the dual-gang switchable is established in the contemporary Jose-canon catalog as the right way to build a fully-loaded Jose preamp — just not on a specific period Marshall 2203 donor.
3. Restricting the toggle to 1959-only would over-claim that the dual-gang is exclusively a Plexi mod. It's better-documented on Plexi (historical accident — the Plexi era ran first), but valid as a Jose-school 2203 build pattern.
Pick the recipe to match your authenticity target
- 1959 + dual-gang push-pull picker: closest match to the documented Sykes (Whitesnake 1987 / Blue Murder) rig. Pair with V0 + cascade + bright-cap reduction + cathode-bypass + diode-clipping (16V) + NFB tightened for the maximally-loaded Sykes recipe. Push-pull OUT for canonical / studio low-volume tracking; IN for the high-volume / stage configuration Jose framed.
- 2203 + dual-gang push-pull picker: matches the topology of Friedman's modern production "Jose" amp rather than a specific period 2203 customer build. A reasonable modder-school-grade authentic 2203 build, but treat it as "modern Jose-school 2203" rather than "the Lynch / period-2203 recipe." For period-faithful 2203 work, single-gang Jose MV (jose-master-volume without dual-gang) more closely matches the documented 2203 record.
Implementation note for JMIL users
The push-pull picker that appears under the Dual-Gang PP mod card defaults to OUT (pre-TS active). In OUT mode the audio + visual are functionally identical to single-gang Jose MV — the only difference is the second post-TS pot drawn in the schematic to communicate "wired in the chassis but bypassed." Flipping the picker to IN re-routes the schematic to show the active signal path through the post-TS pot AND (with diode-clipping on) moves the Zener column to follow the active wiper. The audio chain reroutes correspondingly: the V2a stage's diode clip is suppressed and the post-TS Zener WaveShaper engages. So the picker is a real recipe variant, not just a label.