About this lab — JMIL is an educational sandbox, not a precision amp emulator. The audio chain is a Web-Audio surrogate that reveals what each Jose mod does to the tone; topology, attribution, and mod descriptions are where the lab earns its keep. Content is a best-effort synthesis from forums, videos, books, and articles around the web — sources sometimes conflict, and details may be incomplete or inaccurate.
⚠ Tube amplifiers contain lethal voltages (often 400–500 V DC at high stored charge) that can remain dangerous for days after power-off. If you are not a qualified electronics technician, do not service tube amplifiers. The lab's schematics and mod descriptions are for study, not as DIY instructions.
1959 Plexi Full signal chain — Treble + Normal inputs → V1 parallel → MIX → [V2 cascade] → MV → TONE STACK → V3 PI → 4× EL34 → SPEAKER
Audio A/B
A = stock 1959 SLP (no mods). B = no mods. Toggle A/B during playback for an instant crossfade.
Aggressive 60W ceramic. Pronounced 600 Hz dip + 2 kHz upper-mid peak — modern reissue stack signature.
On-axis halfway between cap & edge — balanced midrange (gentle 2.5 kHz presence).
Tip: plug in your interface and set its preamp gain so peaks land around -12 to -6 dBFS, then click Use my guitar (or press G). The browser will ask permission once.
Wired headphones recommended — Bluetooth adds ~150-300 ms of latency and makes live monitoring unplayable.
Surrogate engine — AudioWorklet per-sample 12AX7 cascade (V1a / V1b / V2a-cold, asymmetric tanh + cathode-bypass bloom) → 5-band tone stack → push-pull power-amp WaveShaper + output-transformer character (HPF / LPF / LF saturation) + NFB-loop steady-state shaping → 2 selectable cab IRs (G12M / V30, real CC0 captures from Freesound). The cab is the biggest sonic delta in the chain; the rest of the chain is in-the-ballpark, not precision-matched to a specific amp.
Original chassis voicing — clean-to-medium crunch with classic British mid honk.· stock · open · cleanish
Gain
7
Bass
3
Mid
7
Treble
6
Master
6
Presence
6
Jose Modifications
0/11 activePREAMP / GAIN MODS
- ADVANCED
Adds a whole gain stage in front. Massive jump in saturation and sustain — turns a Plexi into a Brown-Sound preamp.
- ADVANCED
Tightens palm mutes, kills flub on low E, adds asymmetric harmonic edge.
- EASY
Bypassed = bigger low end and more gain. Unbypassed = tighter, less bass, leaner crunch. Which way the switch reads depends on how the build is wired.
- ADVANCED
Repurposes V2b cathode-follower as a 4th gain stage by relocating the tone stack to V2a plate. Massive sustain and saturation. Documented on DeMartini-era + period hot-rod builds (Vai-era attribution forum-sourced rather than independently verified); attribution to Jose vs Cameron/later-school is debated.
VOICING MODS
- EASY
Cuts ice-pick fizz from the upper highs once you cascade the preamp. Smoother top end, especially on bridge pickups.
- EASY
Smooths the upper-mid grit on V2a — the harsh "spit" on hard pick attack settles into a more vocal feel. Subtle — most obvious in live playing.
INPUT MODS
- MODERATE
Sums Normal + Treble channels. Slightly darker but more mid weight — voicing knob baked into the input.
MASTER VOLUME MODS
- MODERATE
Tone controls always sound the same regardless of volume. Bedroom-volume saturation is finally usable.
- ADVANCED
Adds a second wired-in master at the post-tone-stack position. The push-pull SWITCHES between the two — pre-TS (OUT, low-volume) vs post-TS (IN, high-volume) — per Jose's own framing via Friedman. JMIL defaults to pre-TS active so the audible behavior matches single-gang Jose MV; the visual shows both pots in the chassis (both physically present), which is the Sykes-pattern build and matches Friedman's current production Jose amp.
CLIPPING MODS
- MODERATE
Singing sustain at any volume. Vocal compression on long notes. Lower number on the variant picker = squashier and more compressed; higher = looser and more dynamic.
POWER AMP MODS
- EASY
Spongier feel under the pick. Less power-amp tightness, more bloom on sustained notes.
· Supporting documentation ·
Currently Relevant
Featured entries from the knowledge graph.
Stock vs Modded
0 of 13 components changed on Marshall 1959 Super Lead.
| Position | Stock | Modded | Change | Mod |
|---|---|---|---|---|
| Negative feedback loop | 47kΩ → 8Ω tap | 47kΩ → 8Ω tap | unchanged | — |
| Phase inverter | 12AX7 LTP | 12AX7 LTP | unchanged | — |
| Tone stack | Treble 500pF / Mid+Bass 22nF / Slope 33k | Treble 500pF / Mid+Bass 22nF / Slope 33k | unchanged | — |
| V1 Volume I bright cap | 5nF | 5nF | unchanged | — |
| V1a cathode | 820Ω | 820Ω | unchanged | — |
| V1a cathode bypass | 0.68µF | 0.68µF | unchanged | — |
| V1a plate | 100kΩ | 100kΩ | unchanged | — |
| V1b cathode | 820Ω | 820Ω | unchanged | — |
| V1b plate | 100kΩ | 100kΩ | unchanged | — |
| V2a cathode (Jose: 2.7k unbypassed) | 820Ω | 820Ω | unchanged | — |
| V1b → V2a coupling | 0.022µF | 0.022µF | unchanged | — |
| V2a plate | 100kΩ | 100kΩ | unchanged | — |
| V2b cathode follower | 100kΩ | 100kΩ | unchanged | — |
Beyond the Core Eight
Tier 2 (advanced builds), Tier 3 (commonly-lumped-in but not Jose-originated), and Tier 4 (customer-specific). Read-only by design.