{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "jtm100",
  "url": "https://circuitcodex.com/amps/jtm100/",
  "attribution": "The Analog Maker / Circuit Codex",
  "license": "https://creativecommons.org/licenses/by-sa/4.0/",
  "revision": "ebddc3fd2cf887dca010bbe60487d7391ea6c052",
  "scope": "DC and drawing checks have separate coverage. See included check results and the circuit page; not a dimensioned build template or a physical-build certification.",
  "metadata": {
    "id": "jtm100",
    "name_style": "British 100-watt lead-style",
    "family": "british",
    "era": {
      "start": 1965,
      "end": 1966
    },
    "wattage": 100,
    "tubes": [
      "ECC83",
      "ECC83",
      "ECC83",
      "KT66",
      "KT66",
      "KT66",
      "KT66"
    ],
    "topology": {
      "rectifier": {
        "kind": "solid-state",
        "type": "silicon diode bank"
      },
      "bias": "fixed",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "cathode-follower-fmv"
    },
    "lineage": {
      "derived_from": [
        "jtm45"
      ],
      "influenced": [
        "m1959"
      ]
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Marshall factory drawing, title block \"BASIC SCHEMATIC FOR MARSHALL 100 WATT SUPER TREM AMP / TYPE 1959T\" — the drawing carries no drawing number and no date in its title block; the schematic archive that publishes it files it under the JTM100 heading and dates the sheet 1966. Complement read off the drawing: 4x ECC83 (V1-V4) + 4x KT66 (V5-V8), no rectifier valve — the HT is rectified by two arms of three series silicon diodes (\"DIODES IS107\") behind a standby switch, with a 1 A slow-blow fuse in the HT centre-tap return and a 2 A slow-blow in the mains lead. Every value below is read directly from the published drawing. Four jacks across two channels (68k stoppers, 1M leaks); V1A/V1B 100k plates on one shared 820R cathode with a 25uF bypass; 0.02 couplers into 1M volume pots (100pF bright cap across the second pot); 270k mixers into the V3A grid, the second mixer paralleled by a capacitor whose value is not legible on the archived scan; V3A 100k plate over an unbypassed 820R; V3B DC-coupled cathode follower with a 100k load; FMV stack (56k slope, 270pF/250k treble, 0.02/1M bass, 0.02/25k middle); 0.02 into the long-tailed-pair (82k plate on the tone-stack side, 100k on the other, 47pF across the plates, both 1M leaks returning to the junction BETWEEN them, 470R cathode-to-junction and a 10k tail into a 5k presence pot with a 0.1 wiper cap, a 27k feedback resistor from the 16-ohm tap onto the top of that pot and a 0.1 from the same node up to the V4B grid); 0.1 couplers onto two phase nodes, each with a 220k grid leak to the bias line and a 15k grid stopper feeding ONE valve of its pair while the other valve's grid taps the phase node directly; 1k 5W screen stoppers on all four KT66s; adjustable bias from an HT-tap diode, a 470k trim, 150k, and a 56k/16k divider with 8uF filters; supply reservoir of three series 32uF+32uF pairs, a 20H choke (\"20H CH1\") to the screen node, then 8.2k with 32uF to the phase-inverter rail and 10k/1W with 16uF to the preamp rail; universal mains 110/250 V, T1 secondary leads lettered blue \"100 V LINE\", white \"16 ohm\", yellow \"8 ohm\" and orange \"common\". Not reproduced here; archived at Dr. Tube.",
        "url": "https://www.drtube.com/schematics/marshall/1959t-66.gif"
      },
      {
        "desc": "The same drawing's printed \"VALVE VOLTAGE CHART\" — the measurement basis for the operating-point table. Footnote: \"ALL RESISTORS ARE HALF WATT UNLESS OTHERWISE STATED. ALL VOLTAGES MEASURED TO CHASSIS UNDER NO SIGNAL CONDITIONS WITH AN AVO MODEL 8 Mk II. METER SENSITIVITY 20,000 ohm/V.\" Rows: V1 pins 1/2/3 and 6/7/8 = 285 / 0 / 2 and 285 / 0 / 2; V2 (the tremolo valve, absent from this head) 175 / 0 / 1.5 with its second triode struck through; V3 = 225 / 0 / 1.4 and 400 / 225 / 225; V4 = 310 / \"+\" / 52 and 300 / \"+\" / 52, the phase- inverter grids marked only as positive; V5-V8 pins 3/4 = 560 / 559 each, with the pin-5 control-grid cell a hand-lettered range that the archived scan does not render legibly. The drawing additionally circles node voltages on the schematic itself: 560 at the reservoir, 559 at the screen node, 470 at the phase-inverter rail, 390 at the preamp rail, 16 at the top of the presence pot, and 65/66 at the negative bias filter.",
        "url": "https://www.drtube.com/schematics/marshall/1959t-66.gif"
      },
      {
        "desc": "Dr. Tube schematic-archive Marshall / JTM100 index — the naming and dating frame for this circuit. It records that the first 100-watt amps (1965) used two 50-watt output transformers before a single 100-watt part, that the 100-watt Lead and Bass heads carried left-over JTM45 panels into 1966 (hence \"JTM45/100\") while the 100-watt PA models carried JTM100 panels, that the JTM100s were the first Marshalls with solid-state rectifiers, and that early JTM100s were fitted with KT66s and later ones with EL34s. It is also the source that files the drawing above under JTM100 and dates it 1966.",
        "url": "https://www.drtube.com/marshall-jtm100/"
      },
      {
        "desc": "GEC / M-O Valve Co. KT66 data sheet (Issue 4, April 1963) — anchor for the CC0 KT66 tube model: Va=250 V, Vg2=250 V, Vg1=-15 V -> Ia=85 mA, gm=7 mA/V; screen Ig2=2.5 mA at the Class AB1 push-pull tetrode point (Vg2=300, Vg1=-27); mu(g1-g2)=9.5 from the triode-connection gm.ra. The sheet's 25 W plate-dissipation rating is what the simulated idle current at this circuit's 560 V rail is measured against in the circuit story.",
        "url": "https://frank.pocnet.net/sheets/084/k/KT66_GEC.pdf"
      },
      {
        "desc": "Wikipedia, \"Marshall Amplification\" — the 100-watt heads as a special order from players who wanted more than 45 watts on stage, the 1965 introduction of the 100-watt Super Lead under catalog number 1959, and the later cost-driven move from KT66 to EL34 output valves that ends the circuit documented here.",
        "url": "https://en.wikipedia.org/wiki/Marshall_Amplification"
      }
    ],
    "verification": {
      "status": "draft"
    },
    "added": "2026-08-08T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "This is the plain (non-tremolo) head read off the factory sheet for the tremolo version, the same relationship the corpus's jtm45 entry has with its drawing: the sheet's V2 tremolo valve, its transistor, and the depth network that shunts the V3A grid node are omitted, so the valve numbering follows the drawing and skips V2 (V1 input pair, V3 second stage + cathode follower, V4 phase inverter, V5-V8 the KT66 quartet). The drawing shows four input jacks, two per channel, each with its own 68 kOhm stopper (R1s/R3s channel I into V1A, R2s/R4s channel II into V1B), and hangs each channel's 1 MOhm leak from jack 1's tip (jack 1 = the jack carrying the leak, the lower jack of each pair on the drawing). Capacitor working voltages are NOT given: this drawing prints none for the signal-path parts, and the corpus does not invent ratings. The drawing's own footnote — \"all resistors are half watt unless otherwise stated\" — supplies the wattage for every resistor the sheet does not letter, including the 8.2 kOhm dropper. The factory sheet numbers almost nothing, so every designator here is the corpus's own; the only parts left without one are those no drawing in this entry places: the power transformer, the two mains/HT fuses and the capacitor paralleling the channel II mixer, whose value the archived scan does not render.",
    "items": [
      {
        "ref": "R1s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel I grid stopper, jack 1 (V1A)"
      },
      {
        "ref": "R3s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel I grid stopper, jack 2 (V1A)"
      },
      {
        "ref": "R2s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel II grid stopper, jack 1 (V1B)"
      },
      {
        "ref": "R4s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel II grid stopper, jack 2 (V1B)"
      },
      {
        "ref": "RG1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel I input grid leak, from jack 1's tip to ground"
      },
      {
        "ref": "RG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel II input grid leak, from jack 1's tip to ground"
      },
      {
        "ref": "RL1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1A plate load"
      },
      {
        "ref": "RL2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1B plate load"
      },
      {
        "ref": "RK1",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "Shared ECC83 input cathode bias"
      },
      {
        "ref": "C3",
        "part": "Electrolytic capacitor",
        "value": "25 µF",
        "role": "Shared input cathode bypass"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "V1A → channel I volume"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "V1B → channel II volume"
      },
      {
        "ref": "VR1",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Channel I volume"
      },
      {
        "ref": "VR2",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Channel II volume"
      },
      {
        "ref": "C23",
        "part": "Mica capacitor",
        "value": "100 pF",
        "role": "Bright cap across the channel II volume (VR2)"
      },
      {
        "ref": "RM1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel I mixer"
      },
      {
        "ref": "RM2",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel II mixer"
      },
      {
        "ref": "RL3",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3A plate load"
      },
      {
        "ref": "RK2",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "V3A cathode bias (unbypassed on this sheet)"
      },
      {
        "ref": "RKCF",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Cathode-follower load"
      },
      {
        "ref": "RSL",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Tone-stack slope resistor"
      },
      {
        "ref": "C4",
        "part": "Mica capacitor",
        "value": "270 pF",
        "role": "Tone stack — treble"
      },
      {
        "ref": "VR3",
        "part": "Potentiometer",
        "value": "250 kΩ",
        "role": "Treble"
      },
      {
        "ref": "C5",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Tone stack — bass"
      },
      {
        "ref": "VR4",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Bass"
      },
      {
        "ref": "C6",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Tone stack — middle"
      },
      {
        "ref": "VR5",
        "part": "Linear potentiometer",
        "value": "25 kΩ",
        "role": "Middle"
      },
      {
        "ref": "C7",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "Tone stack → phase-inverter grid"
      },
      {
        "ref": "RLA",
        "part": "Carbon comp resistor",
        "value": "82 kΩ · ½ W",
        "role": "PI plate load (V4A, tone-stack side)"
      },
      {
        "ref": "RLB",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "PI plate load (V4B)"
      },
      {
        "ref": "RGA",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (V4A), returned to the tail junction"
      },
      {
        "ref": "RGB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (V4B), returned to the tail junction"
      },
      {
        "ref": "C8",
        "part": "Film capacitor",
        "value": "0.1 µF",
        "role": "V4B grid AC-coupled to the presence/feedback node"
      },
      {
        "ref": "C12",
        "part": "Mica capacitor",
        "value": "47 pF",
        "role": "PI plate-to-plate phase compensation"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "470 Ω · ½ W",
        "role": "PI cathodes → tail junction"
      },
      {
        "ref": "RT2",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "PI tail, junction → presence pot"
      },
      {
        "ref": "RNFB",
        "part": "Carbon comp resistor",
        "value": "27 kΩ · ½ W",
        "role": "Negative feedback, 16 Ω secondary tap → top of the presence pot"
      },
      {
        "ref": "VR7",
        "part": "Linear potentiometer",
        "value": "5 kΩ",
        "role": "Presence — in series in the phase-inverter tail, not shunting it to ground"
      },
      {
        "ref": "C11",
        "part": "Film capacitor",
        "value": "0.1 µF",
        "role": "Presence-pot wiper to ground"
      },
      {
        "ref": "C9",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "PI → phase-A output grids (V5/V6)"
      },
      {
        "ref": "C10",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "PI → phase-B output grids (V7/V8)"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Phase-A output grid leak, from the bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Phase-B output grid leak, from the bias line"
      },
      {
        "ref": "R5s",
        "part": "Carbon comp resistor",
        "value": "15 kΩ · ½ W",
        "role": "V5 grid stopper (the sheet gives V6's grid no stopper)"
      },
      {
        "ref": "R8s",
        "part": "Carbon comp resistor",
        "value": "15 kΩ · ½ W",
        "role": "V8 grid stopper (the sheet gives V7's grid no stopper)"
      },
      {
        "ref": "RS1",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · 5 W",
        "role": "V5 screen resistor"
      },
      {
        "ref": "RS2",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · 5 W",
        "role": "V6 screen resistor"
      },
      {
        "ref": "RS3",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · 5 W",
        "role": "V7 screen resistor"
      },
      {
        "ref": "RS4",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · 5 W",
        "role": "V8 screen resistor"
      },
      {
        "ref": "L1",
        "part": "Filter choke",
        "value": "20 H",
        "role": "Reservoir → KT66 screen node"
      },
      {
        "ref": "RD1",
        "part": "Carbon comp resistor",
        "value": "8.2 kΩ · ½ W",
        "role": "Rail dropper, screens → phase inverter"
      },
      {
        "ref": "RD2",
        "part": "Power resistor",
        "value": "10 kΩ · 1 W",
        "role": "Rail dropper, phase inverter → preamp"
      },
      {
        "ref": "C13",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 1 (upper)"
      },
      {
        "ref": "C14",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 1 (lower)"
      },
      {
        "ref": "C15",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 2 (upper)"
      },
      {
        "ref": "C16",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 2 (lower)"
      },
      {
        "ref": "C17",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 3 (upper)"
      },
      {
        "ref": "C18",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "HT reservoir, series pair 3 (lower)"
      },
      {
        "ref": "C19",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "Phase-inverter rail filter"
      },
      {
        "ref": "C20",
        "part": "Electrolytic capacitor",
        "value": "16 µF",
        "role": "Preamp rail filter"
      },
      {
        "ref": "D1",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm A (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D2",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm A (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D3",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm A (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D4",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm B (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D5",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm B (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D6",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "HT rectifier, arm B (three in series; the sheet letters them 'DIODES IS107')"
      },
      {
        "ref": "D7",
        "part": "Rectifier diode",
        "value": "IS107",
        "role": "Bias supply rectifier"
      },
      {
        "ref": "VR6",
        "part": "Trimmer potentiometer",
        "value": "470 kΩ",
        "role": "Bias trim"
      },
      {
        "ref": "RB1",
        "part": "Carbon comp resistor",
        "value": "150 kΩ · ½ W",
        "role": "Bias supply series resistor"
      },
      {
        "ref": "RB2",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Bias divider to ground"
      },
      {
        "ref": "RB3",
        "part": "Carbon comp resistor",
        "value": "16 kΩ · ½ W",
        "role": "Bias filter series resistor"
      },
      {
        "ref": "C21",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Bias filter (supply side)"
      },
      {
        "ref": "C22",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Bias filter (grid-line side)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Both input stages (V1A/V1B)"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Second stage + cathode follower (V3A/V3B)"
      },
      {
        "ref": "V4",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Long-tailed-pair phase inverter (V4A/V4B)"
      },
      {
        "ref": "V5",
        "part": "Power tube",
        "value": "KT66",
        "role": "Parallel push-pull output, phase A"
      },
      {
        "ref": "V6",
        "part": "Power tube",
        "value": "KT66",
        "role": "Parallel push-pull output, phase A"
      },
      {
        "ref": "V7",
        "part": "Power tube",
        "value": "KT66",
        "role": "Parallel push-pull output, phase B"
      },
      {
        "ref": "V8",
        "part": "Power tube",
        "value": "KT66",
        "role": "Parallel push-pull output, phase B"
      },
      {
        "ref": "T1",
        "part": "Output transformer",
        "value": "Push-pull, 4x KT66 primary",
        "role": "Output to the speaker; secondary leads lettered on the sheet — blue 100 V line, white 16 Ω, yellow 8 Ω, orange common"
      },
      {
        "ref": "—",
        "part": "Power transformer",
        "value": "110/250 V universal primary · HT + 6.3 V heaters",
        "role": "HT and heater supply"
      },
      {
        "ref": "—",
        "part": "Film capacitor",
        "value": "value illegible on the archived scan",
        "role": "Capacitor drawn in parallel with the channel II mixer RM2 (annotation only)"
      },
      {
        "ref": "—",
        "part": "Fuse",
        "value": "2 A slow-blow",
        "role": "Mains fuse"
      },
      {
        "ref": "—",
        "part": "Fuse",
        "value": "1 A slow-blow",
        "role": "HT centre-tap fuse"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Marshall 100 W factory drawing, printed VALVE VOLTAGE CHART: V1 pins 1/2/3 = 285 / 0 / 2 and pins 6/7/8 = 285 / 0 / 2; V2 (tremolo valve, not in this head) 175 / 0 / 1.5; V3 pins 1/2/3 = 225 / 0 / 1.4 and pins 6/7/8 = 400 / 225 / 225; V4 pins 1/2/3 = 310 / '+' / 52 and pins 6/7/8 = 300 / '+' / 52; V5-V8 pins 3/4 = 560 / 559 each, pin 5 an illegible hand-lettered range. Circled schematic nodes: 560 reservoir, 559 screens, 470 PI rail, 390 preamp rail, 16 presence-pot top, 65/66 bias filter (negative — the filter cans are drawn minus-up).",
    "nodes": {
      "BP2": {
        "chart": 559,
        "tol_pct": 8,
        "note": "KT66 screen node after the 20 H choke (DCR estimated at 150 Ω, as in jtm45) — the drawing's circled 559 and the chart's V5–V8 pin-4 rows agree on it"
      },
      "BP3": {
        "chart": 470,
        "tol_pct": 8,
        "note": "phase-inverter rail after the 8.2 kΩ dropper — circled on the drawing"
      },
      "BP4": {
        "chart": 390,
        "tol_pct": 8,
        "note": "preamp rail after the 10 kΩ/1 W dropper — circled on the drawing. The chart's own V3 pin 6 reads 400 V at the cathode follower's plate, which is this same node; the two printed figures differ by 2.5%"
      },
      "P1A": {
        "chart": 285,
        "tol_pct": 20,
        "note": "ECC83 input plate, channel I (chart V1 pin 1)"
      },
      "P1B": {
        "chart": 285,
        "tol_pct": 20,
        "note": "ECC83 input plate, channel II (chart V1 pin 6)"
      },
      "KA": {
        "chart": 2,
        "tol_pct": 20,
        "note": "shared ECC83 input cathode, 820 Ω with a 25 µF bypass (chart V1 pins 3 and 8)"
      },
      "P3A": {
        "chart": 225,
        "tol_pct": 20,
        "note": "V3A plate = cathode-follower grid, direct-coupled (chart V3 pin 1, and pin 7 reads the same 225 at the follower's grid)"
      },
      "K3A": {
        "chart": 1.4,
        "tol_pct": 20,
        "note": "V3A cathode, 820 Ω unbypassed (chart V3 pin 3)"
      },
      "KCF": {
        "chart": 225,
        "tol_pct": 20,
        "note": "cathode-follower output over its 100 kΩ load (chart V3 pin 8)"
      },
      "PPIA": {
        "chart": 310,
        "tol_pct": 20,
        "note": "phase-inverter plate, 82 kΩ side — the tone-stack-driven triode (chart V4 pin 1)"
      },
      "PPIB": {
        "chart": 300,
        "tol_pct": 20,
        "note": "phase-inverter plate, 100 kΩ side (chart V4 pin 6)"
      },
      "KPI": {
        "chart": 52,
        "tol_pct": 20,
        "note": "phase-inverter cathodes, 470 Ω above the tail junction (chart V4 pins 3 and 8)"
      },
      "PRES": {
        "chart": 16,
        "tol_pct": 20,
        "note": "top of the 5 kΩ presence pot, where the 10 kΩ tail lands and the 27 kΩ feedback resistor arrives — circled on the drawing. Set by phase-inverter current, so it carries the tube-pin tolerance rather than the rail one"
      },
      "JPI": {
        "chart": null,
        "note": "tail junction where both 1 MΩ grid leaks return; the chart prints the phase-inverter grids only as '+' (qualitative)"
      },
      "S5": {
        "chart": null,
        "note": "V5 screen after its 1 kΩ/5 W stopper. The chart's 559 V pin-4 figure is already gated at BP2; this node is informational because the anchor-point KT66 model draws no screen current at this operating point (its screen term goes to zero below Vg2/mu + Vg1 = 0), so the stopper shows no drop and the node reads exactly BP2 — a stated limitation of the corpus's tube models"
      },
      "NGA": {
        "chart": null,
        "note": "phase-A output-grid node: the 0.1 µF coupler, the 220 kΩ leak to the bias line, V6's grid directly and V5's grid through its 15 kΩ stopper. The chart's pin-5 cell is an illegible hand-lettered range, so the modelled -65 V comes from the drawing's circled bias-filter figure instead"
      },
      "NGB": {
        "chart": null,
        "note": "phase-B output-grid node — V7 direct, V8 through its 15 kΩ stopper; same basis as NGA"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 559,
      "sim": 558.448,
      "disputed": false,
      "dev_pct": 0.09874776386404667,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "KT66 screen node after the 20 H choke (DCR estimated at 150 Ω, as in jtm45) — the drawing's circled 559 and the chart's V5–V8 pin-4 rows agree on it",
      "dispute_note": ""
    },
    {
      "node": "BP3",
      "chart": 470,
      "sim": 473.622,
      "disputed": false,
      "dev_pct": 0.7706382978723434,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "phase-inverter rail after the 8.2 kΩ dropper — circled on the drawing",
      "dispute_note": ""
    },
    {
      "node": "BP4",
      "chart": 390,
      "sim": 406.565,
      "disputed": false,
      "dev_pct": 4.247435897435897,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "preamp rail after the 10 kΩ/1 W dropper — circled on the drawing. The chart's own V3 pin 6 reads 400 V at the cathode follower's plate, which is this same node; the two printed figures differ by 2.5%",
      "dispute_note": ""
    },
    {
      "node": "P1A",
      "chart": 285,
      "sim": 274.865,
      "disputed": false,
      "dev_pct": 3.5561403508771896,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "ECC83 input plate, channel I (chart V1 pin 1)",
      "dispute_note": ""
    },
    {
      "node": "P1B",
      "chart": 285,
      "sim": 274.865,
      "disputed": false,
      "dev_pct": 3.5561403508771896,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "ECC83 input plate, channel II (chart V1 pin 6)",
      "dispute_note": ""
    },
    {
      "node": "KA",
      "chart": 2,
      "sim": 2.16,
      "disputed": false,
      "dev_pct": 8.000000000000007,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared ECC83 input cathode, 820 Ω with a 25 µF bypass (chart V1 pins 3 and 8)",
      "dispute_note": ""
    },
    {
      "node": "P3A",
      "chart": 225,
      "sim": 229.601,
      "disputed": false,
      "dev_pct": 2.0448888888888885,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3A plate = cathode-follower grid, direct-coupled (chart V3 pin 1, and pin 7 reads the same 225 at the follower's grid)",
      "dispute_note": ""
    },
    {
      "node": "K3A",
      "chart": 1.4,
      "sim": 1.451,
      "disputed": false,
      "dev_pct": 3.642857142857154,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3A cathode, 820 Ω unbypassed (chart V3 pin 3)",
      "dispute_note": ""
    },
    {
      "node": "KCF",
      "chart": 225,
      "sim": 230.204,
      "disputed": false,
      "dev_pct": 2.3128888888888923,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "cathode-follower output over its 100 kΩ load (chart V3 pin 8)",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 310,
      "sim": 314.9,
      "disputed": false,
      "dev_pct": 1.5806451612903152,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter plate, 82 kΩ side — the tone-stack-driven triode (chart V4 pin 1)",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 300,
      "sim": 303.292,
      "disputed": false,
      "dev_pct": 1.0973333333333244,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter plate, 100 kΩ side (chart V4 pin 6)",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 52,
      "sim": 53.452,
      "disputed": false,
      "dev_pct": 2.7923076923076886,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter cathodes, 470 Ω above the tail junction (chart V4 pins 3 and 8)",
      "dispute_note": ""
    },
    {
      "node": "PRES",
      "chart": 16,
      "sim": 15.352,
      "disputed": false,
      "dev_pct": 4.049999999999998,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "top of the 5 kΩ presence pot, where the 10 kΩ tail lands and the 27 kΩ feedback resistor arrives — circled on the drawing. Set by phase-inverter current, so it carries the tube-pin tolerance rather than the rail one",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": null,
      "sim": 51.741,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "tail junction where both 1 MΩ grid leaks return; the chart prints the phase-inverter grids only as '+' (qualitative)",
      "dispute_note": ""
    },
    {
      "node": "S5",
      "chart": null,
      "sim": 558.448,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "V5 screen after its 1 kΩ/5 W stopper. The chart's 559 V pin-4 figure is already gated at BP2; this node is informational because the anchor-point KT66 model draws no screen current at this operating point (its screen term goes to zero below Vg2/mu + Vg1 = 0), so the stopper shows no drop and the node reads exactly BP2 — a stated limitation of the corpus's tube models",
      "dispute_note": ""
    },
    {
      "node": "NGA",
      "chart": null,
      "sim": -65,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-A output-grid node: the 0.1 µF coupler, the 220 kΩ leak to the bias line, V6's grid directly and V5's grid through its 15 kΩ stopper. The chart's pin-5 cell is an illegible hand-lettered range, so the modelled -65 V comes from the drawing's circled bias-filter figure instead",
      "dispute_note": ""
    },
    {
      "node": "NGB",
      "chart": null,
      "sim": -65,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-B output-grid node — V7 direct, V8 through its 15 kΩ stopper; same basis as NGA",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Within target",
      "summary": "13 reference nodes are within tolerance. The circuit remains a draft awaiting maintainer review.",
      "details": [
        "This compares simulated DC conditions with the cited reference. It does not test sound, physical construction or every part of the circuit."
      ],
      "tone": "checked"
    },
    {
      "id": "schematic",
      "title": "Schematic against DC model",
      "status": "Checked",
      "summary": "Connectivity of modelled components is checked on every change.",
      "details": [
        "Parts outside the DC model need separate checks and source review."
      ],
      "tone": "checked"
    },
    {
      "id": "board",
      "title": "Board against DC model",
      "status": "Checked",
      "summary": "Connectivity of modelled components is checked on every change.",
      "details": [
        "This does not establish heater wiring or physical spacing."
      ],
      "tone": "checked"
    },
    {
      "id": "drawings",
      "title": "Schematic against board",
      "status": "No open findings",
      "summary": "No disagreement is listed in the published comparison.",
      "details": [
        "A finding identifies a difference or a coverage gap. The factory source must decide which drawing, if either, needs correction.",
        "8 sheet-only parts are explicitly excluded: C11, C23, R1s, R2s, R3s, R4s, RG1, RG2. Heaters and the pilot lamp are checked separately."
      ],
      "tone": "checked"
    },
    {
      "id": "heaters",
      "title": "Heater and filament wiring",
      "status": "Not established",
      "summary": "The drawn supply-leg connections have not been established by this check.",
      "details": [
        "Supply-leg grouping still needs confirmation at V1, V3, V4.",
        "No Marshall board-layout sheet was located for the 100-watt Super amplifier; this board is derived from the factory schematic, so no factory drawing can establish its heater legs.",
        "V1: pins [4, 5] are one leg at 6.3 V and opposite legs at 12.6 V"
      ],
      "tone": "attention"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Checked",
      "summary": "11 capacitor markings agree with the model's voltage ordering.",
      "details": [
        "This check uses DC voltage ordering; source review establishes markings the model cannot decide."
      ],
      "tone": "checked"
    }
  ],
  "corrections": [
    {
      "id": "jtm100-input-jacks-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "jtm100"
      ],
      "title": "JTM100 input jacks and grid leaks",
      "description": "The cited drawing shows four input jacks, each with its own 68 kΩ stopper, with each channel's 1 MΩ leak at its first jack's tip. We showed one jack per channel and drew the leak on the grid side. Both are corrected, and no operating point changes. The circuit remains a draft.",
      "commit": "068fa7b43a95ce48b65ce5044050499a4805fd55",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/068fa7b43a95ce48b65ce5044050499a4805fd55"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/jtm100"
}