{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "6g4",
  "url": "https://circuitcodex.com/amps/6g4/",
  "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": "6g4",
    "name_style": "Brown Super-style",
    "family": "other",
    "era": {
      "start": 1960,
      "end": 1963
    },
    "wattage": 40,
    "tubes": [
      "12AX7",
      "12AX7",
      "12AX7",
      "12AX7",
      "12AX7",
      "6L6GC",
      "6L6GC",
      "GZ34"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "GZ34"
      },
      "bias": "fixed",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "tb"
    },
    "sections": {
      "V3A": "excluded — vibrato oscillator: a running phase-shift oscillator has no static DC point"
    },
    "lineage": {
      "derived_from": [
        "5f4"
      ],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Fender 'Super-Amp' Schematic, Model 6G4 (A-FJ) — two-page factory sheet: schematic + companion layout, both carrying the same printed voltages, the schematic page native 2179x1437 px and the layout page 2250x1269 px (the PDF embeds them at 72 ppi, so they are the full resolution of this copy). Title block reads 'FENDER \"SUPER-AMP\" SCHEMATIC / MODEL 6G4 / A-FJ'; the companion page 'FENDER \"SUPER-AMP\" LAYOUT / MODEL 6G4 / A-FJ'. Complement read from the drawing: 5x 7025 (a 12AX7 alias — see the 12AX7 reference page), 2x 6L6GC, GZ34 — matching the layout page's tube row (GZ34, 6L6GC, 6L6GC, 7025 x5) exactly, distinguishing this drawing from the later 6G4-A revision (2x 5881, 2x 12AX7 + 3x 7025, K-FJ), also archived at the same source and cross-read to disambiguate the two. The pin voltages lettered at each socket place every section: V1 carries both channels' first stages (+170 V plates, cathodes joined at +1.4 V); V2 both second stages (+160 V at pin 1, +120 V at pin 6, cathodes joined at +1.1 V); V3 the vibrato oscillator (+130 V plate at pin 1, +1.3 V cathode) and its phase splitter (+180 V plate at pin 6, +1.5 V cathode); V4 the vibrato pair (+320 V at pins 1 and 6, cathodes joined at +3.3 V); V5 the phase inverter (+315 V at pin 1, +310 V at pin 6, cathodes +23 V). Ten triode sections, all drawn. Channels: each has two inputs on 68 kOhm stoppers with a 1 Megohm leak at input 1, a first stage (100 kOhm plate), a .05 uF coupler into a Bass/Treble network (100 kOhm slope, 250 uuF treble capacitor into a 250 kOhm-L Treble pot whose cold lug sits on the slope foot, a 250 kOhm-A Bass pot wired as a divider from the slope foot to ground with .01 uF across its upper section and 10 kOhm across its lower) and a 500 kOhm-L Volume pot, then a second stage. Channel 1 (drawn on top) alone carries a 47 uuF bright capacitor from its Volume's hot lug to the wiper; its second stage loads its plate with 100 kOhm and then a 6800 Ohm decoupling resistor to rail A, and takes its output from their junction through .05 uF into the vibrato. Channel 2's second stage is a single 220 kOhm load, its output .05 uF and 1 Megohm into the node where the vibrato recombines. Harmonic vibrato: channel 1's output feeds a low-pass branch (470 kOhm, .005 to ground, .01 to one grid of V4) and a high-pass branch (220 kOhm / 220 kOhm to ground, 250 uuF to the other grid); V4's sections have 100 kOhm plate loads, a shared 4700 Ohm cathode resistor bypassed by 2-25, and their plates recombine through 470 kOhm each. The oscillator is a three-section phase-shift ladder (.02, .01, .01; Speed 4M-RA with 100 kOhm to ground on the first node, 1 Megohm to the cathode and the vibrato-pedal jack on the second, 1 Megohm grid leak), with a 470 kOhm plate load, 4700 / 25-25 cathode and .03 from plate to ground; its output runs through 4.7 Megohm and .005 onto .1-200 and the 10M-L Intensity control, whose wiper (.05-200 to ground) feeds one vibrato grid through 1 Megohm. The splitter's grid is the node both vibrato grids return to through 1 Megohm each; it carries a 1 Megohm leak and .05-200 to ground and .001 from its plate, its plate a 100 kOhm load, .25 to ground and .05 plus 1 Megohm to the other vibrato grid; cathode 1500 / 25-25. Phase inverter: .001 input coupler, 47 uuF across the plates, 82 kOhm / 100 kOhm 5% plate loads, 820 Ohm shared cathode into a 6.8 kOhm tail, both grids on 1 Megohm leaks; the tail foot carries a 1500 Ohm resistor to ground, the .1-200 that grounds the cold grid for signal, a 10 kOhm negative-feedback resistor back to the output transformer's secondary hot, and the 5 kOhm-linear Presence pot (drawn as a rheostat) in series with a 0.1 uF capacitor. The Presence capacitor's rating is read from the companion LAYOUT page, which letters it .1-200 beside the 5K-L pot. Output: two 6L6GC, 220 kOhm 5% grid leaks off a -55 V bias line, 470 Ohm screen stoppers, grounded cathodes, plates printed +456 V. Rails: the GZ34 into two 20-600 reservoir cans, the standby switch, the choke, +458 V after it (the screens, and every dropper); from there 4700 Ohm 1W to +430 V (the inverter's plate loads), then 56 kOhm 1W to +260 V (rail A: all four channel plate loads); and a separate 56 kOhm 1W to +350 V (the vibrato pair), then a further 56 kOhm 1W to +275 V (the oscillator and splitter), each node on its own 20-600 can. The +350 V, +275 V and +260 V figures and the +23 V inverter cathode are lettered on the layout page only. Bias: a bias-tap rectifier, 8-150, 10k, then 8-150 with a 56k bleeder, -55 V. Notice: 'VOLTAGES READ TO GROUND WITH ELECTRONIC VOLTMETER, VALUES SHOWN + OR -' (the layout page states the drawing's usual '+/- 20%'); resistors 1/2 W if not specified, condensers at least 400 V if not specified. Transformers/choke boxed on the schematic: TR1-8087 (power), TR2-45216 (output), CH-125C1A (choke). Not reproduced here; archived at EL34World.",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_super_6g4_schem.pdf"
      },
      {
        "desc": "Fender 'Super-Amp' Schematic, Model 6G4-A (K-FJ) — the immediately following production revision (2x 5881 output, 12AX7/12AX7/7025x3 preamp), used only as a cross-reference to confirm the 6G4 (this entry) is the earlier 6L6GC/all-7025 revision and to disambiguate the two drawings' near-identical titles and layout. Not used for any 6G4 component value.",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_super_6g4a.pdf"
      },
      {
        "desc": "Mojotone/Ampwares Fender field guide, 'Brownface Super' — 6G4 (2x 6L6GC) and 6G4-A (2x 5881) production window 1960-1963, 40 W factory rating, GZ34, fixed non-adjustable bias, vibrato, two-channel panel with presence, twin 10-inch speakers — the era/wattage citation the Super family page also rests on",
        "url": "https://mojotone.com/blogs/fender-field-guide/fender-brownface-super"
      }
    ],
    "verification": {
      "status": "draft"
    },
    "added": "2026-08-08T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "The drawing prints no channel names; channel 1 is the one drawn at the top of the schematic, whose controls sit beside Speed and Intensity on the panel, and it is the only channel that passes through the vibrato and the only one with a bright capacitor. The oscillator's own network (the ladder, the Speed and Intensity controls, the 4.7 MΩ feed and its smoothing capacitors) is listed in full, but the oscillator is excluded from the DC model: a running phase-shift oscillator has no static operating point. The splitter and the vibrato pair are modelled.",
    "items": [
      {
        "ref": "R1a",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-1 grid stopper from input 1"
      },
      {
        "ref": "R2a",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-1 grid stopper from input 2"
      },
      {
        "ref": "RG1I",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel-1 leak at input 1, to ground (mounted at the jack)"
      },
      {
        "ref": "RL1I",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1A plate load, off rail A"
      },
      {
        "ref": "CC1T",
        "part": "Coupling capacitor",
        "value": "0.05 µF",
        "role": "Channel-1 first-stage plate into the tone network — the stack's coupling capacitor, lettered .05 on the drawing and mounted on the board beside the plate load"
      },
      {
        "ref": "CT1",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Channel-1 treble cap (250MM on the drawing), stack input to the Treble pot's hot lug; mounts at the Treble pot"
      },
      {
        "ref": "VRT1",
        "part": "Potentiometer",
        "value": "250 kΩ-L",
        "role": "Channel-1 treble — hot lug on the 250 pF, cold lug on the slope foot, wiper to the Volume pot"
      },
      {
        "ref": "RS1T",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel-1 tone-stack slope resistor, stack input to the slope foot; mounts at the Treble pot"
      },
      {
        "ref": "VRB1",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Channel-1 bass — a divider from the slope foot to ground: the 0.01 µF across its upper section (hot lug to wiper), the 10 kΩ foot across its lower (wiper to ground)"
      },
      {
        "ref": "CB1T",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Channel-1 bass capacitor, slope foot to the Bass pot's wiper; mounts at the Bass pot"
      },
      {
        "ref": "RSL1",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Channel-1 bass foot resistor, the Bass pot's wiper to ground; mounts at the Bass pot"
      },
      {
        "ref": "VRV1",
        "part": "Potentiometer",
        "value": "500 kΩ-L",
        "role": "Channel-1 volume, fed from the Treble wiper; its own wiper is V2A's grid"
      },
      {
        "ref": "CBR1",
        "part": "Mica capacitor",
        "value": "47 pF",
        "role": "Channel-1 bright capacitor across the Volume pot, hot lug to wiper (47MM on the drawing); mounts at the Volume pot"
      },
      {
        "ref": "RL1D",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V2A plate load, from the plate to the decoupling junction"
      },
      {
        "ref": "RLD1",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "V2A load decoupler, junction to rail A (lettered 6800); channel 1's output is taken at this junction, not at the plate"
      },
      {
        "ref": "CC1D",
        "part": "Coupling capacitor",
        "value": "0.05 µF",
        "role": "Channel-1 output, from the decoupling junction into the vibrato's band-splitting filters"
      },
      {
        "ref": "R1b",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-2 grid stopper from input 1"
      },
      {
        "ref": "R2b",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-2 grid stopper from input 2"
      },
      {
        "ref": "RG2I",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel-2 leak at input 1, to ground (mounted at the jack)"
      },
      {
        "ref": "RL2I",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1B plate load, off rail A"
      },
      {
        "ref": "CC2T",
        "part": "Coupling capacitor",
        "value": "0.05 µF",
        "role": "Channel-2 first-stage plate into the tone network — as CC1T"
      },
      {
        "ref": "CT2",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Channel-2 treble cap — as CT1"
      },
      {
        "ref": "VRT2",
        "part": "Potentiometer",
        "value": "250 kΩ-L",
        "role": "Channel-2 treble — as VRT1"
      },
      {
        "ref": "RS2T",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel-2 tone-stack slope resistor — as RS1T"
      },
      {
        "ref": "VRB2",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Channel-2 bass — a divider from the slope foot to ground, as VRB1"
      },
      {
        "ref": "CB2T",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Channel-2 bass capacitor — as CB1T"
      },
      {
        "ref": "RSL2",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Channel-2 bass foot resistor — as RSL1"
      },
      {
        "ref": "VRV2",
        "part": "Potentiometer",
        "value": "500 kΩ-L",
        "role": "Channel-2 volume, fed from the Treble wiper; its wiper is V2B's grid. Neither page draws a bright capacitor on this control"
      },
      {
        "ref": "RL2D",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "V2B plate load, off rail A — the reason this plate prints +120 V against channel 1's +160 V"
      },
      {
        "ref": "CC2D",
        "part": "Coupling capacitor",
        "value": "0.05 µF",
        "role": "Channel-2 output coupler"
      },
      {
        "ref": "RM2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel-2 mixing resistor into the node where the vibrato pair's outputs recombine"
      },
      {
        "ref": "RKI",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "V1 cathode resistor — both first stages' cathodes joined (the drawing's boxed C)"
      },
      {
        "ref": "CKI",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V1 cathode bypass (25-25 on the drawing)"
      },
      {
        "ref": "RKD",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "V2 cathode resistor — both second stages' cathodes joined (the drawing's boxed D)"
      },
      {
        "ref": "CKD",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V2 cathode bypass (25-25 on the drawing)"
      },
      {
        "ref": "RLP",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Low-band branch series resistor, channel-1 output to the low-pass node"
      },
      {
        "ref": "CLP",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Low-band branch shunt, low-pass node to ground"
      },
      {
        "ref": "CV1",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Low-band coupler, low-pass node to V4A's grid"
      },
      {
        "ref": "RHP1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "High-band branch, channel-1 output to the high-pass node"
      },
      {
        "ref": "RHP2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "High-band branch, high-pass node to ground"
      },
      {
        "ref": "CV2",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "High-band coupler (250MM on the drawing), high-pass node to V4B's grid"
      },
      {
        "ref": "RLV1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V4A (low band) plate load, off the +350 V vibrato-pair supply"
      },
      {
        "ref": "RLV2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V4B (high band) plate load, off the +350 V vibrato-pair supply"
      },
      {
        "ref": "RKV",
        "part": "Carbon comp resistor",
        "value": "4.7 kΩ · ½ W",
        "role": "Vibrato pair's joined cathodes to ground"
      },
      {
        "ref": "CKV",
        "part": "Electrolytic capacitor",
        "value": "2 µF · 25 V",
        "role": "Vibrato pair's cathode bypass (lettered 2-25 on both pages)"
      },
      {
        "ref": "RGV1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "V4A grid return to the splitter's grid"
      },
      {
        "ref": "RGV2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "V4B grid return to the splitter's grid"
      },
      {
        "ref": "RMV1",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "V4A plate into the recombining node"
      },
      {
        "ref": "RMV2",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "V4B plate into the recombining node"
      },
      {
        "ref": "RTOP",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Oscillator plate load, off the +275 V supply"
      },
      {
        "ref": "RTOK",
        "part": "Carbon comp resistor",
        "value": "4.7 kΩ · ½ W",
        "role": "Oscillator cathode resistor"
      },
      {
        "ref": "CTOK",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Oscillator cathode bypass"
      },
      {
        "ref": "CTO3",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Phase-shift ladder, first capacitor: oscillator plate to the first ladder node"
      },
      {
        "ref": "CTO1",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Phase-shift ladder, second capacitor"
      },
      {
        "ref": "CTO2",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Phase-shift ladder, third capacitor, into the oscillator grid"
      },
      {
        "ref": "VRSPD",
        "part": "Reverse-audio potentiometer",
        "value": "4 MΩ-RA",
        "role": "Speed — a rheostat from the first ladder node, in series with RSPD to ground"
      },
      {
        "ref": "RSPD",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Speed end resistor, in series with the Speed control to ground; mounts at the pot"
      },
      {
        "ref": "RTOG1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Phase-shift ladder, second node to the oscillator cathode"
      },
      {
        "ref": "RTOG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Oscillator grid leak, to ground"
      },
      {
        "ref": "JVIB",
        "part": "Jack",
        "value": "vibrato footswitch",
        "role": "Vibrato pedal jack, on the ladder's second node"
      },
      {
        "ref": "CTOP",
        "part": "Film capacitor",
        "value": "0.03 µF",
        "role": "Oscillator plate to ground"
      },
      {
        "ref": "RTOF",
        "part": "Carbon comp resistor",
        "value": "4.7 MΩ · ½ W",
        "role": "Oscillator output feed toward the Intensity control"
      },
      {
        "ref": "CTOF",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Oscillator output coupler, in series with RTOF"
      },
      {
        "ref": "CTX",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Intensity control's hot end to ground"
      },
      {
        "ref": "VRINT",
        "part": "Linear potentiometer",
        "value": "10 MΩ-L",
        "role": "Intensity — from the oscillator feed to ground, wiper to the low-band vibrato grid"
      },
      {
        "ref": "CTW",
        "part": "Film capacitor",
        "value": "0.05 µF · 200 V",
        "role": "Intensity wiper to ground; mounts at the pot"
      },
      {
        "ref": "RWV",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Intensity wiper to V4A's grid"
      },
      {
        "ref": "RLS",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Splitter plate load, off the +275 V supply"
      },
      {
        "ref": "RKS",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "Splitter cathode resistor"
      },
      {
        "ref": "CKS",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Splitter cathode bypass"
      },
      {
        "ref": "RGS",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Splitter grid leak, to ground; its grid is also the node both vibrato grids return to"
      },
      {
        "ref": "CGS",
        "part": "Film capacitor",
        "value": "0.05 µF · 200 V",
        "role": "Splitter grid to ground"
      },
      {
        "ref": "CFS",
        "part": "Mica capacitor",
        "value": "0.001 µF",
        "role": "Splitter plate to grid"
      },
      {
        "ref": "CPS",
        "part": "Film capacitor",
        "value": "0.25 µF",
        "role": "Splitter plate to ground"
      },
      {
        "ref": "CSV",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Splitter output coupler toward V4B's grid"
      },
      {
        "ref": "RSV",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Splitter output into V4B's grid"
      },
      {
        "ref": "VRPRES",
        "part": "Linear potentiometer",
        "value": "5 kΩ-L",
        "role": "Presence — wired as a rheostat, in series with CPRES; that branch parallels RPF from the phase-inverter tail foot to ground"
      },
      {
        "ref": "RPF",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "Tail foot resistor to ground (the schematic letters it 1500; the layout page mounts it at the Presence pot)"
      },
      {
        "ref": "CPRES",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Presence cap, in series with VRPRES to ground — what makes that branch AC-only"
      },
      {
        "ref": "RNFB",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Negative feedback, OT secondary hot → the PI tail foot"
      },
      {
        "ref": "CGB",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Cold PI grid to the foot node (.1-200 on the schematic)"
      },
      {
        "ref": "CPIN",
        "part": "Mica capacitor",
        "value": "0.001 µF",
        "role": "Phase-inverter input coupler, from the recombining node to the hot grid"
      },
      {
        "ref": "RLPA",
        "part": "Carbon comp resistor",
        "value": "82 kΩ · ½ W · 5%",
        "role": "PI plate load (hot side)"
      },
      {
        "ref": "RLPB",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W · 5%",
        "role": "PI plate load (cold side)"
      },
      {
        "ref": "CPP",
        "part": "Mica capacitor",
        "value": "47 pF",
        "role": "Across the two PI plates (47MM on both pages)"
      },
      {
        "ref": "RGPA",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (hot), returned to the tail junction"
      },
      {
        "ref": "RGPB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (cold), returned to the tail junction"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "PI shared cathode resistor"
      },
      {
        "ref": "RT2",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "PI tail, tail junction to the foot node"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.05 µF · 400 V",
        "role": "PI hot plate → V7 grid"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.05 µF · 400 V",
        "role": "PI cold plate → V8 grid"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V7 grid leak, from the -55 V bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V8 grid leak, from the -55 V bias line"
      },
      {
        "ref": "RS1",
        "part": "Wirewound resistor",
        "value": "470 Ω · 1 W",
        "role": "V7 screen resistor, off the post-choke node"
      },
      {
        "ref": "RS2",
        "part": "Wirewound resistor",
        "value": "470 Ω · 1 W",
        "role": "V8 screen resistor, off the post-choke node"
      },
      {
        "ref": "T2",
        "part": "Output transformer",
        "value": "Fender 45216",
        "role": "Push-pull 6L6GC output"
      },
      {
        "ref": "T1",
        "part": "Power transformer",
        "value": "Fender 8087",
        "role": "HT + heaters + rectifier filament"
      },
      {
        "ref": "C10",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Reservoir at the GZ34 cathode, ahead of the standby switch and choke (the drawing puts two 20-600 cans here)"
      },
      {
        "ref": "CH1",
        "part": "Filter choke",
        "value": "Fender 125C1A",
        "role": "Filter choke from the +460 V node, where the output transformer's centre tap lands, to the +458 V screen and dropper node"
      },
      {
        "ref": "CF4",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter at the post-choke node (+458 V: screens and every dropper)"
      },
      {
        "ref": "RD1",
        "part": "Power resistor",
        "value": "4.7 kΩ · 1 W",
        "role": "Dropper, post-choke node to the +430 V phase-inverter supply (the schematic letters it 4700 1W)"
      },
      {
        "ref": "CF5",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter at the +430 V phase-inverter supply"
      },
      {
        "ref": "RD2",
        "part": "Power resistor",
        "value": "56 kΩ · 1 W",
        "role": "Dropper, +430 V node to rail A (+260 V, both channels)"
      },
      {
        "ref": "CF6",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter at rail A"
      },
      {
        "ref": "RD3",
        "part": "Power resistor",
        "value": "56 kΩ · 1 W",
        "role": "Dropper, post-choke node to the +350 V vibrato-pair supply"
      },
      {
        "ref": "CF7",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter at the +350 V vibrato-pair supply"
      },
      {
        "ref": "RD4",
        "part": "Power resistor",
        "value": "56 kΩ · 1 W",
        "role": "Dropper, +350 V node to the +275 V oscillator and splitter supply"
      },
      {
        "ref": "CF8",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter at the +275 V oscillator and splitter supply"
      },
      {
        "ref": "DBIAS",
        "part": "Rectifier (bias)",
        "value": "silicon diode",
        "role": "Bias-supply rectifier"
      },
      {
        "ref": "RBIAS1",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Bias bleeder — from the -55 V node to ground (A-FJ)"
      },
      {
        "ref": "RBIAS2",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Bias-supply series resistor"
      },
      {
        "ref": "CBIAS",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 150 V",
        "role": "Bias-supply filter"
      },
      {
        "ref": "CBIAS2",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 150 V",
        "role": "Bias output filter — the second 8 µF at the -55 V node, beside the 56 kΩ bleeder (A-FJ)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Both channels' first stages: V1A channel 1 (pins 6-8), V1B channel 2 (pins 1-3), cathodes joined"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Both channels' second stages: V2A channel 1 (pins 1-3, +160 V), V2B channel 2 (pins 6-8, +120 V), cathodes joined"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Vibrato oscillator V3A (pins 1-3, excluded from the DC model) and its phase splitter V3B (pins 6-8)"
      },
      {
        "ref": "V4",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Vibrato pair: V4A low band (pins 1-3), V4B high band (pins 6-8), cathodes joined"
      },
      {
        "ref": "V5",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Long-tailed-pair phase inverter: V5A hot (pins 1-3, +315 V), V5B cold (pins 6-8, +310 V)"
      },
      {
        "ref": "V7",
        "part": "Power tube",
        "value": "6L6GC",
        "role": "Push-pull output (hot side)"
      },
      {
        "ref": "V8",
        "part": "Power tube",
        "value": "6L6GC",
        "role": "Push-pull output (cold side)"
      },
      {
        "ref": "V9",
        "part": "Rectifier tube",
        "value": "GZ34",
        "role": "Full-wave rectifier (V9A/V9B)"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender 'Super-Amp' Schematic, Model 6G4 (A-FJ). Schematic page: +458 (after the choke; screens and droppers), +456 (6L6GC plates), +430 (phase-inverter supply), +315/+310 (phase-inverter plates), +320/+320 and +3.3 (vibrato pair plates and joined cathodes), +130 and +1.3 (vibrato oscillator plate and cathode — excluded, reported here only), +180 and +1.5 (the oscillator's phase splitter), +170/+1.4 (both first stages, cathodes joined), +160 (channel 1 second stage), +120 (channel 2 second stage), +1.1 (the second stages' joined cathodes), -55 (6L6GC fixed bias). Layout page, in addition: +350 (vibrato-pair supply), +275 (oscillator and splitter supply), +260 (rail A, both channels), +23 (phase-inverter cathodes).",
    "nodes": {
      "BC": {
        "chart": 430,
        "tol_pct": 8,
        "note": "phase-inverter supply, after the 4.7 kΩ · 1 W dropper from the post-choke node — printed on both pages"
      },
      "BA": {
        "chart": 260,
        "tol_pct": 10,
        "note": "rail A, after a 56 kΩ · 1 W dropper from the +430 V node; it feeds all four channel plate loads. Printed on the layout page only"
      },
      "BV": {
        "chart": 350,
        "tol_pct": 10,
        "note": "vibrato-pair supply, after a 56 kΩ · 1 W dropper from the post-choke node. Printed on the layout page only. Simulates a few volts high: the oscillator's own draw, which also passes through this dropper, is not modelled (see the next node)"
      },
      "BL": {
        "chart": 275,
        "tol_pct": 10,
        "note": "supply for the oscillator's 470 kΩ and the splitter's 100 kΩ, after a second 56 kΩ · 1 W dropper. Printed on the layout page only, as a small vertical label; the units digit is the least certain glyph, and the 10% band holds any reading of it. Simulates about 9% high because the oscillator is excluded from the model and its running draw with it — about 0.3 mA on the chart's own +130 V plate reading. With a 0.31 mA sink standing in for it, this node lands at 275 V and the vibrato-pair supply at 346 V"
      },
      "P1I": {
        "chart": 170,
        "tol_pct": 20,
        "note": "channel-1 first stage plate (V1, 100 kΩ load off rail A)"
      },
      "P2I": {
        "chart": 170,
        "tol_pct": 20,
        "note": "channel-2 first stage plate (V1's other section, 100 kΩ load off rail A)"
      },
      "KI": {
        "chart": 1.4,
        "tol_pct": 20,
        "note": "both first stages' joined cathodes over one 820 Ω / 25 µF pair (the drawing's boxed C)"
      },
      "P1D": {
        "chart": 160,
        "tol_pct": 20,
        "note": "channel-1 second stage plate (V2): 100 kΩ, then a 6.8 kΩ decoupling resistor to rail A, output taken between them"
      },
      "P2D": {
        "chart": 120,
        "tol_pct": 20,
        "note": "channel-2 second stage plate (V2's other section): a single 220 kΩ load off rail A — the reason it prints lower than channel 1"
      },
      "KD": {
        "chart": 1.1,
        "tol_pct": 20,
        "note": "both second stages' joined cathodes over one 820 Ω / 25 µF pair (the drawing's boxed D)"
      },
      "PV1": {
        "chart": 320,
        "tol_pct": 20,
        "note": "vibrato pair, low-band section plate (V4, 100 kΩ load off the vibrato-pair supply)"
      },
      "PV2": {
        "chart": 320,
        "tol_pct": 20,
        "note": "vibrato pair, high-band section plate"
      },
      "KV": {
        "chart": 3.3,
        "tol_pct": 20,
        "note": "vibrato pair's joined cathodes over 4.7 kΩ / 2 µF"
      },
      "PS": {
        "chart": 180,
        "tol_pct": 20,
        "note": "oscillator's phase splitter plate (V3, 100 kΩ load). Reads high with its supply — see BL"
      },
      "KS": {
        "chart": 1.5,
        "tol_pct": 20,
        "note": "phase splitter cathode over 1.5 kΩ / 25 µF"
      },
      "PPIA": {
        "chart": 315,
        "tol_pct": 20,
        "note": "phase-inverter plate, 82 kΩ (hot) side"
      },
      "PPIB": {
        "chart": 310,
        "tol_pct": 20,
        "note": "phase-inverter plate, 100 kΩ (cold) side"
      },
      "KPI": {
        "chart": 23,
        "tol_pct": 20,
        "note": "phase-inverter joined cathodes, above the 820 Ω — printed at the socket on the layout page only"
      },
      "JPI": {
        "chart": null,
        "note": "phase-inverter tail junction (820 Ω / 6.8 kΩ), the grid-leak return — printed on neither page"
      },
      "G61": {
        "chart": -55,
        "tol_pct": 8,
        "note": "6L6GC (V7) grid, fixed bias through a 220 kΩ · 5% leak from the driven -55 V supply — exact by construction (ideal source, no drop across the leak at zero grid current)"
      },
      "G62": {
        "chart": -55,
        "tol_pct": 8,
        "note": "6L6GC (V8) grid, fixed bias through a 220 kΩ · 5% leak from the driven -55 V supply — exact by construction"
      },
      "BS1": {
        "chart": 458,
        "tol_pct": 10,
        "note": "6L6GC (V7) screen after its 470 Ω · 1 W stopper. The drawing prints +458 V at the post-choke node the screens hang from; the model drives that node at the printed +458 V"
      },
      "BS2": {
        "chart": 458,
        "tol_pct": 10,
        "note": "6L6GC (V8) screen after its own 470 Ω · 1 W stopper — same basis as BS1"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BC",
      "chart": 430,
      "sim": 430.265,
      "disputed": false,
      "dev_pct": 0.06162790697674101,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "phase-inverter supply, after the 4.7 kΩ · 1 W dropper from the post-choke node — printed on both pages",
      "dispute_note": ""
    },
    {
      "node": "BA",
      "chart": 260,
      "sim": 252.448,
      "disputed": false,
      "dev_pct": 2.904615384615382,
      "tol_pct": 10,
      "gated": true,
      "within": true,
      "note": "rail A, after a 56 kΩ · 1 W dropper from the +430 V node; it feeds all four channel plate loads. Printed on the layout page only",
      "dispute_note": ""
    },
    {
      "node": "BV",
      "chart": 350,
      "sim": 358.979,
      "disputed": false,
      "dev_pct": 2.565428571428567,
      "tol_pct": 10,
      "gated": true,
      "within": true,
      "note": "vibrato-pair supply, after a 56 kΩ · 1 W dropper from the post-choke node. Printed on the layout page only. Simulates a few volts high: the oscillator's own draw, which also passes through this dropper, is not modelled (see the next node)",
      "dispute_note": ""
    },
    {
      "node": "BL",
      "chart": 275,
      "sim": 300.938,
      "disputed": false,
      "dev_pct": 9.431999999999995,
      "tol_pct": 10,
      "gated": true,
      "within": true,
      "note": "supply for the oscillator's 470 kΩ and the splitter's 100 kΩ, after a second 56 kΩ · 1 W dropper. Printed on the layout page only, as a small vertical label; the units digit is the least certain glyph, and the 10% band holds any reading of it. Simulates about 9% high because the oscillator is excluded from the model and its running draw with it — about 0.3 mA on the chart's own +130 V plate reading. With a 0.31 mA sink standing in for it, this node lands at 275 V and the vibrato-pair supply at 346 V",
      "dispute_note": ""
    },
    {
      "node": "P1I",
      "chart": 170,
      "sim": 167.671,
      "disputed": false,
      "dev_pct": 1.3700000000000045,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "channel-1 first stage plate (V1, 100 kΩ load off rail A)",
      "dispute_note": ""
    },
    {
      "node": "P2I",
      "chart": 170,
      "sim": 167.671,
      "disputed": false,
      "dev_pct": 1.3700000000000045,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "channel-2 first stage plate (V1's other section, 100 kΩ load off rail A)",
      "dispute_note": ""
    },
    {
      "node": "KI",
      "chart": 1.4,
      "sim": 1.39,
      "disputed": false,
      "dev_pct": 0.714285714285715,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "both first stages' joined cathodes over one 820 Ω / 25 µF pair (the drawing's boxed C)",
      "dispute_note": ""
    },
    {
      "node": "P1D",
      "chart": 160,
      "sim": 155.312,
      "disputed": false,
      "dev_pct": 2.9299999999999926,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "channel-1 second stage plate (V2): 100 kΩ, then a 6.8 kΩ decoupling resistor to rail A, output taken between them",
      "dispute_note": ""
    },
    {
      "node": "P2D",
      "chart": 120,
      "sim": 126.995,
      "disputed": false,
      "dev_pct": 5.829166666666671,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "channel-2 second stage plate (V2's other section): a single 220 kΩ load off rail A — the reason it prints lower than channel 1",
      "dispute_note": ""
    },
    {
      "node": "KD",
      "chart": 1.1,
      "sim": 1.213,
      "disputed": false,
      "dev_pct": 10.272727272727272,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "both second stages' joined cathodes over one 820 Ω / 25 µF pair (the drawing's boxed D)",
      "dispute_note": ""
    },
    {
      "node": "PV1",
      "chart": 320,
      "sim": 322.39,
      "disputed": false,
      "dev_pct": 0.7468749999999957,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "vibrato pair, low-band section plate (V4, 100 kΩ load off the vibrato-pair supply)",
      "dispute_note": ""
    },
    {
      "node": "PV2",
      "chart": 320,
      "sim": 322.39,
      "disputed": false,
      "dev_pct": 0.7468749999999957,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "vibrato pair, high-band section plate",
      "dispute_note": ""
    },
    {
      "node": "KV",
      "chart": 3.3,
      "sim": 3.439,
      "disputed": false,
      "dev_pct": 4.212121212121219,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "vibrato pair's joined cathodes over 4.7 kΩ / 2 µF",
      "dispute_note": ""
    },
    {
      "node": "PS",
      "chart": 180,
      "sim": 197.293,
      "disputed": false,
      "dev_pct": 9.607222222222225,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "oscillator's phase splitter plate (V3, 100 kΩ load). Reads high with its supply — see BL",
      "dispute_note": ""
    },
    {
      "node": "KS",
      "chart": 1.5,
      "sim": 1.555,
      "disputed": false,
      "dev_pct": 3.6666666666666625,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase splitter cathode over 1.5 kΩ / 25 µF",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 315,
      "sim": 311.726,
      "disputed": false,
      "dev_pct": 1.0393650793650797,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter plate, 82 kΩ (hot) side",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 310,
      "sim": 302.244,
      "disputed": false,
      "dev_pct": 2.5019354838709584,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter plate, 100 kΩ (cold) side",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 23,
      "sim": 24.326,
      "disputed": false,
      "dev_pct": 5.7652173913043505,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter joined cathodes, above the 820 Ω — printed at the socket on the layout page only",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": null,
      "sim": 22.091,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-inverter tail junction (820 Ω / 6.8 kΩ), the grid-leak return — printed on neither page",
      "dispute_note": ""
    },
    {
      "node": "G61",
      "chart": -55,
      "sim": -55,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6L6GC (V7) grid, fixed bias through a 220 kΩ · 5% leak from the driven -55 V supply — exact by construction (ideal source, no drop across the leak at zero grid current)",
      "dispute_note": ""
    },
    {
      "node": "G62",
      "chart": -55,
      "sim": -55,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6L6GC (V8) grid, fixed bias through a 220 kΩ · 5% leak from the driven -55 V supply — exact by construction",
      "dispute_note": ""
    },
    {
      "node": "BS1",
      "chart": 458,
      "sim": 457.89,
      "disputed": false,
      "dev_pct": 0.024017467248911274,
      "tol_pct": 10,
      "gated": true,
      "within": true,
      "note": "6L6GC (V7) screen after its 470 Ω · 1 W stopper. The drawing prints +458 V at the post-choke node the screens hang from; the model drives that node at the printed +458 V",
      "dispute_note": ""
    },
    {
      "node": "BS2",
      "chart": 458,
      "sim": 457.89,
      "disputed": false,
      "dev_pct": 0.024017467248911274,
      "tol_pct": 10,
      "gated": true,
      "within": true,
      "note": "6L6GC (V8) screen after its own 470 Ω · 1 W stopper — same basis as BS1",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Within target",
      "summary": "22 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: C10, CF4, CF5, CF6, CF7, CF8, RG1I, RG2I. Heaters and the pilot lamp are checked separately."
      ],
      "tone": "checked"
    },
    {
      "id": "heaters",
      "title": "Heater and filament wiring",
      "status": "Partial",
      "summary": "Some circuits are checked; other heater connections remain unestablished.",
      "details": [
        "Supply-leg grouping still needs confirmation at V1, V2, V3, V4, V5.",
        "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": "Partial",
      "summary": "1 capacitor marking cannot be confirmed by the DC model.",
      "details": [
        "CTOK: CTOK.a: reaches only ground, through RTOK"
      ],
      "tone": "attention"
    }
  ],
  "corrections": [],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/6g4"
}