{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "aa1164",
  "url": "https://circuitcodex.com/amps/aa1164/",
  "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": "aa1164",
    "name_style": "Blackface Princeton Reverb-style",
    "family": "blackface",
    "era": {
      "start": 1964,
      "end": 1967
    },
    "wattage": 12,
    "tubes": [
      "12AX7",
      "12AT7",
      "12AX7",
      "12AX7",
      "6V6GT",
      "6V6GT",
      "5U4GB"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "5U4GB"
      },
      "bias": "fixed",
      "phase_inverter": "cathodyne",
      "tone_stack": "tb"
    },
    "lineage": {
      "derived_from": [],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Fender \"Princeton Reverb-Amp AA1164\" drawing (drawing no. D 045427 rev A, sheet 1 of 2 schematic + sheet 2 of 2 layout): every component value AND the printed voltage chart read directly from the published sheets. Supply chain +420 (rectifier reservoir / output-transformer centre tap) - 1k-1W - +400 (6V6 screens, reverb-driver transformer, tremolo plate load) - 18k-1W - +320 - 18k-1W - +240 (preamp and phase-inverter rail); 6V6 plates +410 with grids on a -34 V fixed-bias line through 220k 5% leaks and no screen stoppers; preamp plates +160 over 100k with 1500 Ohm cathodes at +1.3/+1.2; reverb driver 12AT7 both sections paralleled, 2200 Ohm shared cathode at +8.0 into TR3; reverb recovery 220k grid resistor, 100k plate; driver stage cathode 1500 Ohm bypassed in series with an unbypassed 47 Ohm carrying the 2700 Ohm speaker feedback; split-load phase inverter 56k plate / 1k + 56k cathode reading +200/+50/+49 with a 1M grid leak returned to the 1k-56k junction; tremolo oscillator 220k plate load and 3300 Ohm cathode at +260/+2.4 injecting into the bias line through a 250k-L Intensity control. Transformers TR1-125P1B (340-0-340 V), TR2-125A10B, TR3-125A20B. Notice: \"Voltages read to ground with electronic voltmeter. Values shown + or - 20%. All resistors 1/2 watt 10% tolerance if not specified. All capacitors at least 400 volt rating if not specified.\" The preamp bottle is labelled 7025 (a 12AX7 alias). Tone stack re-read at lug level 2026-08-03: the sheet draws the AA964's two-knob ladder (100k slope + 250p off the plate node, 0.1 to the treble-lug/bass node, bass rheostat over the 0.047/6.8k foot, treble-wiper output; the layout sheet mounts the 6.8k on the bass pot, grounded to its case). Not reproduced here; archived at EL34World",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_reverb_aa1164.pdf"
      },
      {
        "desc": "Fender AA1164 schematic sheet, archived separately from the two-sheet drawing — a second print of the same supply-chain values and the same voltage chart",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_reverb_aa1164_schem.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-08-02T00:00:00.000Z",
      "max_deviation_pct": 11.5
    },
    "contributors": [
      "TheAnalogMaker"
    ],
    "sections": {
      "V4A": "excluded — the tremolo's phase-shift oscillator: a running oscillator has no static operating point; its missing ~0.6 mA reads BB, BC and BD about half a volt high"
    }
  },
  "parts": {
    "notes": "The schematic draws both instrument jacks (1 and 2) with their normalling contacts; this sheet draws them as the two input labels, with the 1 MΩ leak at jack 1's tip, jack side of its 68 kΩ stopper, where both K-FD pages put it. Tube reference designators run from the input end of the chassis (V1 nearest the jacks) — the drawing labels socket types, not V-numbers, and the section split shown here is read off the layout sheet's per-pin voltages. Tremolo-oscillator and reverb-tank interconnect parts are listed, but the oscillator's DC point is excluded from the netlist (see the circuit story). The 125P1B is the power transformer Fender shared across the Champ, the Princeton and the Princeton Reverb, and the HT winding is not annotated the same way on every sheet: this drawing prints 340-0-340 V, as does the Princeton AA964, while the Champ AA764 sheet prints 320-0-320 V for the same part number. Each entry records the figure its own drawing prints.",
    "items": [
      {
        "ref": "R1a",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Input grid stopper (jack 1)"
      },
      {
        "ref": "R1b",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Input grid stopper (jack 2)"
      },
      {
        "ref": "RGN1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Input leak, jack 1's tip to ground (jack side of R1a); the grid's DC return through R1a"
      },
      {
        "ref": "RLN1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1a plate load"
      },
      {
        "ref": "RKN1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V1a cathode bias"
      },
      {
        "ref": "CKN1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V1a cathode bypass"
      },
      {
        "ref": "CT",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Treble cap"
      },
      {
        "ref": "VRT",
        "part": "Audio-taper potentiometer",
        "value": "250 kΩ-A",
        "role": "Treble"
      },
      {
        "ref": "RS",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Tone-stack slope resistor"
      },
      {
        "ref": "CB1",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "Tone-stack bass cap, slope node to the bass pot"
      },
      {
        "ref": "VRB",
        "part": "Audio-taper potentiometer",
        "value": "250 kΩ-A",
        "role": "Bass"
      },
      {
        "ref": "CB2",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "Tone-stack middle-leg cap, slope node to the bleed resistor"
      },
      {
        "ref": "RSL",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "Tone-stack bleed resistor"
      },
      {
        "ref": "VRVOL",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ-A",
        "role": "Volume"
      },
      {
        "ref": "RLN2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1b plate load"
      },
      {
        "ref": "RKN2",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V1b cathode bias"
      },
      {
        "ref": "CKN2",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V1b cathode bypass"
      },
      {
        "ref": "CC1",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "V1b output coupling"
      },
      {
        "ref": "RMIX",
        "part": "Carbon comp resistor",
        "value": "3.3 MΩ · ½ W",
        "role": "Dry-signal mixing resistor into the driver grid"
      },
      {
        "ref": "CMIX",
        "part": "Mica capacitor",
        "value": "10 pF",
        "role": "Bright cap across the dry mixing resistor"
      },
      {
        "ref": "RMR",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Reverb mixing resistor (Reverb wiper → driver grid)"
      },
      {
        "ref": "CRS",
        "part": "Coupling capacitor",
        "value": "500 pF",
        "role": "Reverb send coupling to the driver grid"
      },
      {
        "ref": "RGRD",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Reverb-driver grid leak"
      },
      {
        "ref": "RKRD",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Reverb-driver shared cathode bias"
      },
      {
        "ref": "CKRD",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Reverb-driver cathode bypass"
      },
      {
        "ref": "TR3",
        "part": "Reverb transformer",
        "value": "Fender 125A20B",
        "role": "Reverb driver → tank input"
      },
      {
        "ref": "TANK",
        "part": "Reverb tank",
        "value": "spring reverb unit",
        "role": "Reverb delay line (input and output jacks)"
      },
      {
        "ref": "RGR1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Reverb-recovery grid resistor (tank output)"
      },
      {
        "ref": "RLR1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3a plate load"
      },
      {
        "ref": "RKR1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V3a cathode bias"
      },
      {
        "ref": "CKR1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V3a cathode bypass"
      },
      {
        "ref": "CCR1",
        "part": "Coupling capacitor",
        "value": "0.003 µF",
        "role": "Reverb-recovery output coupling"
      },
      {
        "ref": "VRREV",
        "part": "Linear potentiometer",
        "value": "100 kΩ-L",
        "role": "Reverb"
      },
      {
        "ref": "RLD1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3b plate load"
      },
      {
        "ref": "RKD1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V3b cathode bias (bypassed)"
      },
      {
        "ref": "CKD1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V3b cathode bypass"
      },
      {
        "ref": "RKD2",
        "part": "Carbon comp resistor",
        "value": "47 Ω · ½ W",
        "role": "V3b unbypassed cathode resistor / feedback injection point"
      },
      {
        "ref": "RNFB",
        "part": "Carbon comp resistor",
        "value": "2.7 kΩ · ½ W",
        "role": "Negative feedback, speaker → driver cathode"
      },
      {
        "ref": "CC2",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "Driver → phase-inverter coupling"
      },
      {
        "ref": "RLPI",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Phase-inverter plate load"
      },
      {
        "ref": "RKPI",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · ½ W",
        "role": "Phase-inverter cathode bias resistor"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Phase-inverter cathode load"
      },
      {
        "ref": "RGPI",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Phase-inverter grid leak, returned to the 1 kΩ / 56 kΩ junction"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "Inverter plate → V5 grid"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "Inverter cathode → V6 grid"
      },
      {
        "ref": "RTOP",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Tremolo oscillator plate load"
      },
      {
        "ref": "RKTO",
        "part": "Carbon comp resistor",
        "value": "3.3 kΩ · ½ W",
        "role": "Tremolo oscillator cathode bias"
      },
      {
        "ref": "CKTO",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Tremolo oscillator cathode bypass"
      },
      {
        "ref": "CTO1",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Tremolo phase-shift cap, oscillator plate → Speed node"
      },
      {
        "ref": "CTO2",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Tremolo phase-shift cap, Speed node → pedal node"
      },
      {
        "ref": "CTO3",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Tremolo phase-shift cap, pedal node → oscillator grid"
      },
      {
        "ref": "RTO1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Tremolo oscillator grid leak"
      },
      {
        "ref": "RTO2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Tremolo pedal node → oscillator cathode"
      },
      {
        "ref": "RSPD",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Speed-network series resistor, with the Speed control from the Speed node to ground"
      },
      {
        "ref": "VRSPD",
        "part": "Reverse-audio potentiometer",
        "value": "3 MΩ-RA",
        "role": "Speed"
      },
      {
        "ref": "RTOUT",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Tremolo oscillator output series resistor"
      },
      {
        "ref": "CTO4",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Tremolo output shunt to ground"
      },
      {
        "ref": "CINT",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "Tremolo output coupling into the Intensity control"
      },
      {
        "ref": "VRINT",
        "part": "Linear potentiometer",
        "value": "250 kΩ-L",
        "role": "Intensity — its track runs from the 0.1 µF coupler to the bias supply's filter node, and its wiper is the −34 V grid-leak line"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V5 grid leak, from the −34 V bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V6 grid leak, from the −34 V bias line"
      },
      {
        "ref": "TR2",
        "part": "Output transformer",
        "value": "Fender 125A10B",
        "role": "Push-pull 6V6 output"
      },
      {
        "ref": "JEXT",
        "part": "Jack",
        "value": "external speaker",
        "role": "Parallel speaker output"
      },
      {
        "ref": "RB1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W · 5%",
        "role": "Bias-supply feed from the HT winding"
      },
      {
        "ref": "DB1",
        "part": "Rectifier (bias)",
        "value": "silicon diode",
        "role": "Bias-supply rectifier"
      },
      {
        "ref": "CB3",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 50 V",
        "role": "Bias-supply filter"
      },
      {
        "ref": "RB2",
        "part": "Carbon comp resistor",
        "value": "22 kΩ · ½ W",
        "role": "Bias-supply bleeder"
      },
      {
        "ref": "TR1",
        "part": "Power transformer",
        "value": "Fender 125P1B · 340-0-340 V",
        "role": "HT + heaters + rectifier filament"
      },
      {
        "ref": "CF1",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 450 V",
        "role": "Reservoir filter (+420 V, OT centre tap)"
      },
      {
        "ref": "R1K",
        "part": "Wirewound resistor",
        "value": "1 kΩ · 1 W",
        "role": "Dropper, reservoir → screen rail"
      },
      {
        "ref": "CF2",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 450 V",
        "role": "Filter, screen rail (+400 V)"
      },
      {
        "ref": "RD1",
        "part": "Wirewound resistor",
        "value": "18 kΩ · 1 W",
        "role": "Dropper, screen rail → +320 V node"
      },
      {
        "ref": "CF3",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 450 V",
        "role": "Filter, +320 V node"
      },
      {
        "ref": "RD2",
        "part": "Wirewound resistor",
        "value": "18 kΩ · 1 W",
        "role": "Dropper, +320 V → preamp rail"
      },
      {
        "ref": "CF4",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 450 V",
        "role": "Filter, preamp / phase-inverter rail (+240 V)"
      },
      {
        "ref": "RH1",
        "part": "Carbon comp resistor",
        "value": "100 Ω · ½ W",
        "role": "Heater hum-balance resistor"
      },
      {
        "ref": "RH2",
        "part": "Carbon comp resistor",
        "value": "100 Ω · ½ W",
        "role": "Heater hum-balance resistor"
      },
      {
        "ref": "F1",
        "part": "Fuse",
        "value": "1 A slo-blo",
        "role": "Mains fuse"
      },
      {
        "ref": "SW1",
        "part": "Switch",
        "value": "SPST",
        "role": "AC switch"
      },
      {
        "ref": "SW2",
        "part": "Switch",
        "value": "SPDT",
        "role": "Ground switch (period; not in modern builds)"
      },
      {
        "ref": "CDEATH",
        "part": "Ceramic capacitor",
        "value": "0.047 µF · 600 V",
        "role": "Ground-switch cap (period; not in modern builds)"
      },
      {
        "ref": "JVIB",
        "part": "Jack",
        "value": "vibrato footswitch",
        "role": "Grounds the phase-shift ladder's pedal node to stop the oscillator"
      },
      {
        "ref": "JREV",
        "part": "Jack",
        "value": "reverb footswitch",
        "role": "Wired to the Reverb Output jack's tip — the recovery grid — so the closed pedal grounds the grid and mutes the reverb"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Preamp input stage + second stage (V1a/V1b)"
      },
      {
        "ref": "V2",
        "part": "Preamp/driver tube",
        "value": "12AT7",
        "role": "Reverb driver (both sections paralleled)"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Reverb recovery + driver/mixer stage (V3a/V3b)"
      },
      {
        "ref": "V4",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Tremolo oscillator (DC point excluded) + split-load phase inverter (V4a/V4b)"
      },
      {
        "ref": "V5",
        "part": "Power tube",
        "value": "6V6GT",
        "role": "Push-pull output (inverter-plate side)"
      },
      {
        "ref": "V6",
        "part": "Power tube",
        "value": "6V6GT",
        "role": "Push-pull output (inverter-cathode side)"
      },
      {
        "ref": "V7",
        "part": "Rectifier tube",
        "value": "5U4GB",
        "role": "Full-wave rectifier"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender AA1164 Princeton Reverb-Amp drawing, printed voltages: +420 (reservoir / OT centre tap), +410 (6V6 plates), +400 (6V6 screens, reverb-driver plate), +320 (middle supply node), +260/+2.4 (tremolo oscillator, excluded), +240 (preamp / phase-inverter rail), +200/+50/+49 (phase inverter), +160 (preamp, reverb-recovery and driver plates), +8.0 (reverb-driver cathode), +1.3 and +1.2 (preamp cathodes), -34 (6V6 fixed bias)",
    "nodes": {
      "BB": {
        "chart": 400,
        "tol_pct": 8,
        "note": "screen / reverb-driver rail, solved through the 1 kΩ-1 W dropper from the +420 reservoir"
      },
      "BC": {
        "chart": 320,
        "tol_pct": 8,
        "note": "middle supply node between the two 18 kΩ-1 W droppers; nothing else taps it, so the chart's two 80 V drops must match"
      },
      "BD": {
        "chart": 240,
        "tol_pct": 8,
        "note": "preamp and phase-inverter rail, after the second 18 kΩ-1 W dropper"
      },
      "PN1": {
        "chart": 160,
        "tol_pct": 20,
        "note": "preamp input-stage plate, 100 kΩ from +240"
      },
      "KN1": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "preamp input-stage cathode over 1.5 kΩ"
      },
      "PN2": {
        "chart": 160,
        "tol_pct": 20,
        "note": "preamp second-stage plate, 100 kΩ from +240"
      },
      "KN2": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "preamp second-stage cathode over 1.5 kΩ"
      },
      "PRD": {
        "chart": 400,
        "tol_pct": 20,
        "note": "reverb-driver 12AT7 plate (paralleled sections), off the screen rail through the TR3 primary DCR"
      },
      "KRD": {
        "chart": 8,
        "tol_pct": 20,
        "note": "reverb-driver 12AT7 shared cathode over 2.2 kΩ"
      },
      "PR1": {
        "chart": 160,
        "tol_pct": 20,
        "note": "reverb-recovery plate, 100 kΩ from +240"
      },
      "KR1": {
        "chart": 1.2,
        "tol_pct": 20,
        "note": "reverb-recovery cathode over 1.5 kΩ"
      },
      "PD1": {
        "chart": 160,
        "tol_pct": 20,
        "note": "driver / mixer plate, 100 kΩ from +240"
      },
      "KD1": {
        "chart": 1.2,
        "tol_pct": 20,
        "note": "driver / mixer cathode, 1.5 kΩ above the 47 Ω feedback resistor"
      },
      "PPI": {
        "chart": 200,
        "tol_pct": 20,
        "note": "split-load phase-inverter plate, 56 kΩ from +240"
      },
      "KPI": {
        "chart": 50,
        "tol_pct": 20,
        "note": "split-load phase-inverter cathode, above the 1 kΩ"
      },
      "JPI": {
        "chart": 49,
        "tol_pct": 20,
        "note": "phase-inverter 1 kΩ / 56 kΩ junction — the grid-leak return that biases the stage"
      },
      "G61": {
        "chart": -34,
        "tol_pct": 8,
        "note": "6V6 (V5) grid, fixed bias through the 220 kΩ-5% leak from the −34 V supply"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BB",
      "chart": 400,
      "sim": 407.492,
      "disputed": false,
      "dev_pct": 1.8730000000000044,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "screen / reverb-driver rail, solved through the 1 kΩ-1 W dropper from the +420 reservoir",
      "dispute_note": ""
    },
    {
      "node": "BC",
      "chart": 320,
      "sim": 327.592,
      "disputed": false,
      "dev_pct": 2.372499999999995,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "middle supply node between the two 18 kΩ-1 W droppers; nothing else taps it, so the chart's two 80 V drops must match",
      "dispute_note": ""
    },
    {
      "node": "BD",
      "chart": 240,
      "sim": 247.693,
      "disputed": false,
      "dev_pct": 3.2054166666666717,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "preamp and phase-inverter rail, after the second 18 kΩ-1 W dropper",
      "dispute_note": ""
    },
    {
      "node": "PN1",
      "chart": 160,
      "sim": 160.819,
      "disputed": false,
      "dev_pct": 0.5118749999999928,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "preamp input-stage plate, 100 kΩ from +240",
      "dispute_note": ""
    },
    {
      "node": "KN1",
      "chart": 1.3,
      "sim": 1.303,
      "disputed": false,
      "dev_pct": 0.23076923076922243,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "preamp input-stage cathode over 1.5 kΩ",
      "dispute_note": ""
    },
    {
      "node": "PN2",
      "chart": 160,
      "sim": 160.819,
      "disputed": false,
      "dev_pct": 0.5118749999999928,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "preamp second-stage plate, 100 kΩ from +240",
      "dispute_note": ""
    },
    {
      "node": "KN2",
      "chart": 1.3,
      "sim": 1.303,
      "disputed": false,
      "dev_pct": 0.23076923076922243,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "preamp second-stage cathode over 1.5 kΩ",
      "dispute_note": ""
    },
    {
      "node": "PRD",
      "chart": 400,
      "sim": 406.765,
      "disputed": false,
      "dev_pct": 1.6912499999999966,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-driver 12AT7 plate (paralleled sections), off the screen rail through the TR3 primary DCR",
      "dispute_note": ""
    },
    {
      "node": "KRD",
      "chart": 8,
      "sim": 7.998,
      "disputed": false,
      "dev_pct": 0.024999999999997247,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-driver 12AT7 shared cathode over 2.2 kΩ",
      "dispute_note": ""
    },
    {
      "node": "PR1",
      "chart": 160,
      "sim": 160.819,
      "disputed": false,
      "dev_pct": 0.5118749999999928,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-recovery plate, 100 kΩ from +240",
      "dispute_note": ""
    },
    {
      "node": "KR1",
      "chart": 1.2,
      "sim": 1.303,
      "disputed": false,
      "dev_pct": 8.583333333333332,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-recovery cathode over 1.5 kΩ",
      "dispute_note": ""
    },
    {
      "node": "PD1",
      "chart": 160,
      "sim": 162.01,
      "disputed": false,
      "dev_pct": 1.2562499999999943,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "driver / mixer plate, 100 kΩ from +240",
      "dispute_note": ""
    },
    {
      "node": "KD1",
      "chart": 1.2,
      "sim": 1.325,
      "disputed": false,
      "dev_pct": 10.416666666666668,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "driver / mixer cathode, 1.5 kΩ above the 47 Ω feedback resistor",
      "dispute_note": ""
    },
    {
      "node": "PPI",
      "chart": 200,
      "sim": 193.047,
      "disputed": false,
      "dev_pct": 3.476500000000002,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "split-load phase-inverter plate, 56 kΩ from +240",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 50,
      "sim": 55.622,
      "disputed": false,
      "dev_pct": 11.244,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "split-load phase-inverter cathode, above the 1 kΩ",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": 49,
      "sim": 54.646,
      "disputed": false,
      "dev_pct": 11.52244897959184,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter 1 kΩ / 56 kΩ junction — the grid-leak return that biases the stage",
      "dispute_note": ""
    },
    {
      "node": "G61",
      "chart": -34,
      "sim": -34,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6V6 (V5) grid, fixed bias through the 220 kΩ-5% leak from the −34 V supply",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "17 reference nodes are within tolerance. Maintainer verification is recorded for 2026-08-02; changes since then are awaiting maintainer re-review.",
      "details": [
        "The circuit's facts (netlist, reference voltages, parts list, both drawings' connections, capacitor polarity marks and heater declarations) have changed since the maintainer's review, or no review fingerprint is on record yet. The badge stands on its date until the maintainer re-reviews.",
        "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.",
        "10 sheet-only parts are explicitly excluded: CB3, CDEATH, DB1, F1, R1a, R1b, RB1, RB2, RH1, RH2. 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, V2, V3, V4.",
        "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": "2 capacitor markings cannot be confirmed by the DC model.",
      "details": [
        "CKTO: CKTO.b: reaches only ground, through RKTO",
        "CKD1: CKD1.b: on KD1B, which has no simulated volts"
      ],
      "tone": "attention"
    }
  ],
  "corrections": [
    {
      "id": "aa1164-input-reverb-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "aa1164"
      ],
      "title": "AA1164 input grid leak and reverb footswitch",
      "description": "The 1 MΩ input leak now hangs from jack 1's tip, on the jack side of its 68 kΩ resistor, and the reverb footswitch jack connects to the reverb recovery grid, as the factory drawing shows. The schematic had the leak on the grid and the footswitch on the reverb control's wiper. No operating point changes.",
      "commit": "dbfa9ab1200623c104fe4669d263333c40364212",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/dbfa9ab1200623c104fe4669d263333c40364212"
    },
    {
      "id": "aa1164-speed-sections-2026-09-22",
      "date": "2026-09-22",
      "amps": [
        "aa1164"
      ],
      "title": "AA1164 Speed-control connection and input-valve sections",
      "description": "The schematic now straps the Speed control's wiper to the lug carrying the ground resistor and assigns the input and second-stage valve sections to the factory drawing's pins. The schematic and board comparison now agrees for this circuit.",
      "commit": "6cc33f1",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/6cc33f1"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/aa1164"
}