One of the key debates in the late-70s/early-80s LA Marshall-mod scene was where to put the extra gain stage — at the front of the preamp (Jose's choice), or after the master volume / EQ network (Lee Jackson's early choice, Paul Rivera-influenced).
Lee Jackson's earliest mod work — influenced by Paul Rivera's Princeton/Deluxe modifications — put an extra gain stage after the master volume and EQ, trying to mimic the saturated-power-amp character of a Plexi cranked on 10. Per Dave Friedman (Marshall Modification Project, Dec 2025, ~[13:48–14:24]): the approach *"never quite worked out … too bassy, too bloated, not very tight."* Later, Jackson moved the gain stage to the front of the preamp — *"and that was better."*
Why front-end cascading wins for the cranked-Marshall-at-lower-volume goal: 1. Tone stack still sculpts the EQ. Putting clipping AFTER the tone stack means the tone stack shapes the clean signal and the diode/tube nonlinearity operates on a flat post-EQ spectrum. This produces a "synthetic" EQ-then-clip character that doesn't replicate the gestalt of a cranked Plexi (where the EQ and clipping interact throughout the chain). 2. The phase inverter and power amp see the clipped signal rather than producing the clipping themselves. This sounds different from power-amp clipping in important ways — the bloat, the bass-handling, the touch sensitivity. 3. Putting the gain stage at the front means cascaded preamp tubes are clipping in a way that mimics multiple cranked Marshall plexi stages stacking — which is the actual sonic target of "cranked Plexi at lower volume."
Lee Jackson's later (better) work: - Front-end gain stage on Marshall conversions. - Tube-buffered effects loops (an addition Jose wouldn't make — see cameron-relationship for the tradition of adding loops to Jose amps that Jose refused to add himself). - M1000 head and Ampeg mods showing the same front-end-cascading instinct.
The pedagogical point for JMIL: the lab's V0-stage mod is *specifically* a front-end addition (V0 → V1 → V2 → tone stack → MV → PI → power amp). The 4th-gain-stage / tone-stack-relocation mod is also a front-end approach (it pushes the tone stack downstream so a 4th gain stage can fit upstream). Neither lab mod attempts the "extra gain stage after the master" pattern because the historical record (Lee Jackson's own self-correction) shows it doesn't produce the Jose-target sound.
Caveat on naming: Lee Jackson the modder is sometimes confused with the bassist of the same name. The amp-mod Lee Jackson is the one who designed the Ampeg VL series and Crate Vintage Club, among others.
Extended lineage (from Amp Panel #13, March 2026): Lee Jackson's Ampeg VL-1002 (1989) drew topologically from the Laney AOR per Friedman — *"judging from the era when this was made, I would say Lee Jackson got some ideas from Laney. For sure. I would verbatim say that."* Two distinct Lee-Jackson product lines exist: the Metaltronix VO (which has the extra gain stage in front, Jose-influence direction) and the Ampeg VL/1002 (which has the cathode-follower-driving-tone-stack architecture, closer to JCM800 / Laney AOR derivation). He also used oversized filter caps (~470µF stacked-series building blocks) in some builds — adjacent to John Suhr's similar approach in Doug Aldrich's amp (~800µF main filter caps, early-90s).