{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "ac15",
  "url": "https://circuitcodex.com/amps/ac15/",
  "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": "ac15",
    "name_style": "Vox AC15-style",
    "family": "vox",
    "era": {
      "start": 1960,
      "end": 1963
    },
    "wattage": 15,
    "tubes": [
      "EF86",
      "ECC83",
      "ECC83",
      "ECC83",
      "ECC82",
      "EL84",
      "EL84",
      "EZ81"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "EZ81"
      },
      "bias": "cathode",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "top-cut"
    },
    "lineage": {
      "derived_from": [],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "JMI factory drawing OA/031 — title block reads 'JENNINGS MUSICAL INDUSTRIES LTD. / \"VOX AC.15\" AMPLIFIER CIRCUIT No. 3 / DRAWING FOR WORKS USE ONLY / Scale: N/A / DATE 29-4-60', with a modifications box noting 'C42 ADDED 7-2-61' and a deletion. THIS is the revision documented here — the third AC15 circuit, the one that reinstated the phase-shifting vibrato as an integral part of the amplifier. Complement read from the drawing: EF86 (Normal channel), ECC83 phase inverter, ECC83 Vibrato/Tremolo first stage, ECC82 modulator, ECC83 vibrato oscillator, 2x EL84, EZ81 rectifier. Values read directly from the drawing where its published scan resolves them: EL84 pair on one shared 130 ohm / 5 W cathode resistor with a 50 uF / 50 V bypass, 100 ohm screen stoppers, 1.5 kohm grid stoppers, 220 kohm grid leaks; 100 kohm phase-inverter anode loads with a 1.2 kohm shared cathode over a 47 kohm tail; 250 kohm log Top Cut with a 0.005 uF cap; 22 kohm supply droppers; EF86 stage on a 220 kohm anode load, 1 M screen feed, 2.2 kohm / 25 uF cathode; annotated working voltages +315 V rail, +90 V EF86 anode, +220 V phase-inverter anode, +310 V EL84 anodes, and +325 V at the reservoir ahead of the choke — the one annotation outside the part of the amplifier this netlist models; Haddon mains and output transformers, Radiospares choke; asterisks mark the alternate values for the AC15 Bass. Not reproduced here; archived at the Vox AC30 history site.",
        "url": "https://www.voxac30.org.uk/vox_ac15_third_circuit.html"
      },
      {
        "desc": "Published redrawn 1960 AC15 schematic hosted by Hoffman Amplifiers — the legibility cross-reference. It is a modern redraw, not a factory document, but it resolves every value the OA/031 scan leaves ambiguous and it agrees with the factory drawing everywhere both can be read, including the shared 130 ohm output cathode resistor, the 100 ohm screens, the 47 kohm phase-inverter tail and the annotated working voltages. Where the two differ it is only in modern preferred values for the same part — 0.0047 uF against the drawing's 0.005 uF Top Cut cap, 47 uF against the drawing's 50 uF cathode can, 220 pF against the drawing's 250 pF Brilliance cap — and the FACTORY value is the one recorded in this entry.",
        "url": "https://el34world.com/Hoffman/files/AC15_schematic.png"
      },
      {
        "desc": "Vox AC30 history archive, 'The Vox AC/15 - third circuit, mid 1960 on' — the dating and identity evidence for this revision: OA/031 drawn 29 April 1960 and signed off by Dick Denney, alongside the AC30/4 and AC30/6 drawings OA/032 and OA/026 of the same date; production from serial numbers around 4060 into the 5000s; the EL84 cathode resistor named as R22 on the drawing and given as 130 ohms, a value chosen in late 1957; transformers commissioned from Haddon, choke from Radiospares; 'Normal' and 'Bass' voicings marked on the drawing with asterisks.",
        "url": "https://www.voxac30.org.uk/vox_ac15_third_circuit.html"
      },
      {
        "desc": "Independent published circuit analysis of the vintage Vox AC15 — third reading of the same stage values (EF86 220 kohm anode load, 1 M screen feed, 2.2 kohm / 25 uF cathode; long-tailed-pair inverter with 100 kohm anode loads, 1.2 kohm cathode and 47 kohm tail; EL84 pair on 130 ohms shared cathode bias with 100 ohm screen stoppers) and of the working voltages, agreeing with the factory drawing",
        "url": "https://www.ampbooks.com/mobile/classic-circuits/vox-ac15/"
      },
      {
        "desc": "Vox AC30 history archive, 'The Vox AC30/6, black control panels' — the evidence for what happened to the EF86 when the design was scaled up. Two AC30/6 circuits are documented: the early one, first drawn 29 April 1960 (drawing OA/026, the same date as this amp's OA/031), which carries the EF86 on the Normal channel; and the post-'list of changes' circuit introduced in May 1961, in which 'the EF86 is replaced by an ECC83 - one half each for the first stage of the Brilliant and Normal channels', alongside changes lifting gain and treble response",
        "url": "https://www.voxac30.org.uk/vox_ac30_6_black_panels.html"
      },
      {
        "desc": "Philips/Mullard EL84 data sheet, January 1969 (A.F. Output Pentode) — anchor for the CC0 EL84 tube model and its noval basing: Va=250 V, Vg2=250 V, Vg1=-7.3 V -> Ia=48 mA, Ig2=5.5 mA, S=11.3 mA/V, mu(g1-g2)=19",
        "url": "https://frank.pocnet.net/sheets/010/e/EL84.pdf"
      },
      {
        "desc": "Philips/Mullard EF86 data sheet, January 1970 (A.F. Pentode) — anchor for the CC0 EF86 tube model and its noval basing: Va=250 V, Vg2=140 V, Vg1=-2.2 V -> Ia=3.0 mA, Ig2=0.6 mA, S=2.2 mA/V, mu(g1-g2)=38. Its operating-characteristics table also publishes the exact 220 kohm / 1 M / 2.2 kohm A.F.-amplifier network this amp's Normal channel uses",
        "url": "https://frank.pocnet.net/sheets/010/e/EF86.pdf"
      },
      {
        "desc": "Philips EZ81 data sheet, January 1970 (Double Anode Rectifying Tube) — basing and the anode characteristic (fig. 7Z00030-5.26.ha) behind the CC0 EZ81 model; the sheet tabulates no per-anode voltage drop, only whole-rectifier system rows, so that model's anchor is read from the published curve and is labelled as such",
        "url": "https://frank.pocnet.net/sheets/010/e/EZ81.pdf"
      }
    ],
    "verification": {
      "status": "draft"
    },
    "added": "2026-08-02T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ],
    "sections": {
      "V5": "excluded — the Vibrato/Tremolo channel's two gain stages (both sections), left out with the whole channel: they share one derived supply node with the oscillator, which has no static operating point",
      "V6": "excluded — the Vibrato/Tremolo modulator, left out with the whole channel (see V5)",
      "V7": "excluded — the Vibrato/Tremolo phase-shift oscillator (one section) and the section that feeds Depth (the other): a running oscillator has no static operating point"
    }
  },
  "parts": {
    "notes": "Where the factory drawing and the published redraw give different values for the same part, the FACTORY value is listed and the redraw's modern equivalent noted alongside. Coupling and cathode-bypass capacitor VALUES are open at DC and do not enter the operating-point netlist; they are listed for completeness. Parts belonging to the Vibrato/Tremolo channel are marked — that channel is outside the DC netlist's scope (see the circuit story), so its values are read from the drawing but not simulated; the parts of it whose wiring the published scan does not resolve carry no designator and are drawn on the schematic as annotation, not as asserted connections. Asterisked values on the drawing mark the alternate parts for the AC15 Bass; the Normal-voicing values are the ones listed.",
    "items": [
      {
        "ref": "JN1",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Normal channel input (dual-jack arrangement)"
      },
      {
        "ref": "JN2",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Normal channel input (dual-jack arrangement)"
      },
      {
        "ref": "RIN1",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal channel input grid stopper, dual-jack arrangement"
      },
      {
        "ref": "RIN2",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal channel input grid stopper, dual-jack arrangement"
      },
      {
        "ref": "JN",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Normal channel input (single-jack arrangement, drawn as the alternate)"
      },
      {
        "ref": "RGS1",
        "part": "Carbon comp resistor",
        "value": "33 kΩ · ½ W",
        "role": "Normal channel grid stopper, single-jack arrangement"
      },
      {
        "ref": "RG1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Normal channel input grid leak"
      },
      {
        "ref": "JV1",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Vibrato/Tremolo channel input (dual-jack arrangement)"
      },
      {
        "ref": "JV2",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Vibrato/Tremolo channel input (dual-jack arrangement)"
      },
      {
        "ref": "RIN3",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Vibrato/Tremolo input grid stopper"
      },
      {
        "ref": "RIN4",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Vibrato/Tremolo input grid stopper"
      },
      {
        "ref": "JV",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Vibrato/Tremolo channel input (single-jack arrangement)"
      },
      {
        "ref": "RGS2",
        "part": "Carbon comp resistor",
        "value": "33 kΩ · ½ W",
        "role": "Vibrato/Tremolo grid stopper, single-jack arrangement"
      },
      {
        "ref": "RG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Vibrato/Tremolo input grid leak"
      },
      {
        "ref": "RD1",
        "part": "Power resistor",
        "value": "22 kΩ · 3 W",
        "role": "Rail dropper, +315 V → Normal-channel supply node"
      },
      {
        "ref": "CF1",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Normal-channel supply smoothing"
      },
      {
        "ref": "RL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "EF86 anode load"
      },
      {
        "ref": "RS1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "EF86 screen-grid feed"
      },
      {
        "ref": "CS1",
        "part": "Film capacitor",
        "value": "0.1 µF",
        "role": "EF86 screen-grid bypass"
      },
      {
        "ref": "RK1",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "EF86 cathode bias"
      },
      {
        "ref": "CK1",
        "part": "Electrolytic capacitor",
        "value": "25 µF",
        "role": "EF86 cathode bypass"
      },
      {
        "ref": "CO1",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "EF86 anode → Brilliance switch → Normal volume"
      },
      {
        "ref": "SWBRIL",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Brilliance switch — closed it shorts CBR out for full-range coupling, open it leaves CBR in circuit (panel-marked for the Normal channel)"
      },
      {
        "ref": "CBR",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Series treble-only coupling cap, bridged by the Brilliance switch (the published redraw prints 220 pF)"
      },
      {
        "ref": "VR1",
        "part": "Log potentiometer",
        "value": "500 kΩ",
        "role": "Normal channel volume"
      },
      {
        "ref": "RD2",
        "part": "Power resistor",
        "value": "22 kΩ · 3 W",
        "role": "Rail dropper, +315 V → phase-inverter supply node"
      },
      {
        "ref": "CF2",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Phase-inverter supply smoothing"
      },
      {
        "ref": "CIN1",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Normal volume → phase-inverter grid (side A)"
      },
      {
        "ref": "CIN2",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Vibrato/Tremolo volume → phase-inverter grid (side B)"
      },
      {
        "ref": "RLA",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Phase-inverter anode load (side A)"
      },
      {
        "ref": "RLB",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Phase-inverter anode load (side B)"
      },
      {
        "ref": "RGA",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Phase-inverter grid leak (side A), returned to the tail junction"
      },
      {
        "ref": "RGB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Phase-inverter grid leak (side B), returned to the tail junction"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "1.2 kΩ · ½ W",
        "role": "Phase-inverter shared cathode resistor"
      },
      {
        "ref": "RT2",
        "part": "Carbon comp resistor",
        "value": "47 kΩ · ½ W",
        "role": "Phase-inverter tail (junction → ground)"
      },
      {
        "ref": "VR3",
        "part": "Log potentiometer",
        "value": "250 kΩ",
        "role": "Top Cut — in series with a cap across the two phase-inverter outputs"
      },
      {
        "ref": "CTC",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Top Cut capacitor (the published redraw prints 0.0047 µF)"
      },
      {
        "ref": "CC1",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Phase inverter → EL84 grid (upper)"
      },
      {
        "ref": "CC2",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Phase inverter → EL84 grid (lower)"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "EL84 grid leak (upper), returned to ground"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "EL84 grid leak (lower), returned to ground"
      },
      {
        "ref": "RST1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "EL84 grid stopper (upper)"
      },
      {
        "ref": "RST2",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "EL84 grid stopper (lower)"
      },
      {
        "ref": "RSC1",
        "part": "Power resistor",
        "value": "100 Ω · 3 W",
        "role": "EL84 screen-grid stopper (upper)"
      },
      {
        "ref": "RSC2",
        "part": "Power resistor",
        "value": "100 Ω · 3 W",
        "role": "EL84 screen-grid stopper (lower)"
      },
      {
        "ref": "R22",
        "part": "Power resistor",
        "value": "130 Ω · 5 W",
        "role": "SHARED EL84 cathode bias resistor — the whole bias arrangement for the pair (factory designator; the published redraw prints a 10 W part)"
      },
      {
        "ref": "CKO",
        "part": "Electrolytic capacitor",
        "value": "50 µF · 50 V",
        "role": "EL84 cathode bypass (the published redraw prints 47 µF)"
      },
      {
        "ref": "RD3",
        "part": "Power resistor",
        "value": "22 kΩ · 3 W",
        "role": "Vibrato/Tremolo channel rail dropper from +315 V"
      },
      {
        "ref": "CF3",
        "part": "Electrolytic capacitor",
        "value": "33 µF",
        "role": "Vibrato/Tremolo supply smoothing"
      },
      {
        "ref": "RKV1",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Vibrato/Tremolo first-stage cathode bias"
      },
      {
        "ref": "CKV1",
        "part": "Electrolytic capacitor",
        "value": "25 µF",
        "role": "Vibrato/Tremolo first-stage cathode bypass"
      },
      {
        "ref": "RKV2",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "Vibrato/Tremolo second-stage cathode bias"
      },
      {
        "ref": "RGV",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Vibrato/Tremolo inter-stage grid return"
      },
      {
        "ref": "CVC",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Vibrato/Tremolo inter-stage coupler"
      },
      {
        "ref": "VR2",
        "part": "Log potentiometer",
        "value": "500 kΩ",
        "role": "Vibrato/Tremolo channel volume"
      },
      {
        "ref": "—",
        "part": "Carbon comp resistor",
        "value": "150 kΩ · ½ W",
        "role": "Vibrato/Tremolo supply dropper (annotation only)"
      },
      {
        "ref": "—",
        "part": "Carbon comp resistor",
        "value": "12 kΩ · ½ W",
        "role": "Vibrato/Tremolo supply dropper (annotation only)"
      },
      {
        "ref": "—",
        "part": "Carbon comp resistor",
        "value": "22 kΩ · ½ W",
        "role": "Vibrato/Tremolo supply dropper (annotation only)"
      },
      {
        "ref": "—",
        "part": "Tone network (2 positions)",
        "value": "0.0022 µF / 500 pF · 68 kΩ · 330 kΩ · 500 pF / 100 pF · 22 kΩ",
        "role": "TONE I / TONE II — the switched two-position voicing network of the Vibrato/Tremolo channel (annotation only)"
      },
      {
        "ref": "—",
        "part": "Phase-shift ladder",
        "value": "5 × 0.0047 µF with 4 × 1 MΩ",
        "role": "The vibrato phase-shift chain feeding the Vibrato/Tremolo volume (annotation only)"
      },
      {
        "ref": "—",
        "part": "Modulator network",
        "value": "470 kΩ · 1 MΩ · 180 kΩ · 10 kΩ · 1.5 kΩ · 47 kΩ · 0.1 µF · 220 pF · 0.033 µF",
        "role": "ECC82 modulator around the phase-shift ladder (annotation only)"
      },
      {
        "ref": "—",
        "part": "Oscillator network",
        "value": "3 × 0.01 µF with 1 MΩ returns · 220 kΩ · 270 kΩ · 560 kΩ · 22 kΩ · 1.5 kΩ · 3.9 kΩ · 25 µF · 0.1 µF · 0.022 µF",
        "role": "ECC83 phase-shift oscillator — the vibrato/tremolo generator (annotation only)"
      },
      {
        "ref": "—",
        "part": "Potentiometer",
        "value": "1 MΩ",
        "role": "Depth (annotation only)"
      },
      {
        "ref": "—",
        "part": "Potentiometer",
        "value": "3 MΩ",
        "role": "Speed (annotation only)"
      },
      {
        "ref": "—",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Vibrato/Tremolo speed fast/slow — on the back of the Depth pot (annotation only)"
      },
      {
        "ref": "—",
        "part": "Footswitch",
        "value": "SPST",
        "role": "Vibrato/Tremolo on/off, remote (annotation only)"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Footswitch jack (annotation only)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "EF86",
        "role": "Normal channel pentode preamp"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Long-tailed-pair phase inverter — both channels mix here"
      },
      {
        "ref": "V3",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output (upper)"
      },
      {
        "ref": "V4",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output (lower)"
      },
      {
        "ref": "V5",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Vibrato/Tremolo channel first stage"
      },
      {
        "ref": "V6",
        "part": "Preamp tube",
        "value": "ECC82 (12AU7)",
        "role": "Vibrato/Tremolo modulator"
      },
      {
        "ref": "V7",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Vibrato/Tremolo phase-shift oscillator"
      },
      {
        "ref": "V8",
        "part": "Rectifier tube",
        "value": "EZ81 (6CA4)",
        "role": "Full-wave rectifier"
      },
      {
        "ref": "T1",
        "part": "Power transformer",
        "value": "Haddon OF 031 · HT secondary 300-0-300 V at 130 mA · 6.3 V, 4 A heater winding · primary taps 115/160/205/225/245 V",
        "role": "Mains/HT transformer"
      },
      {
        "ref": "T2",
        "part": "Output transformer",
        "value": "Haddon OA 063 · push-pull EL84 primary · 8 Ω / 15 Ω secondary taps",
        "role": "Output transformer"
      },
      {
        "ref": "CH1",
        "part": "Filter choke",
        "value": "Radiospares OA 123 · 10–20 H · 100 mA DC",
        "role": "Smoothing choke between reservoir and HT rail"
      },
      {
        "ref": "CR1",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Reservoir filter, EZ81 cathode side"
      },
      {
        "ref": "CR2",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Smoothing filter after the choke"
      },
      {
        "ref": "SW1",
        "part": "Toggle switch",
        "value": "DPST",
        "role": "Mains on/off"
      },
      {
        "ref": "SW2",
        "part": "Rotary switch",
        "value": "5-position",
        "role": "Mains voltage selector — 115/160/205/225/245 V"
      },
      {
        "ref": "SW7",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Standby — breaks the HT rail after the smoothing choke"
      },
      {
        "ref": "F1",
        "part": "Fuse",
        "value": "2 A",
        "role": "Mains fuse — value from the published redraw; the factory scan does not resolve this figure"
      },
      {
        "ref": "PL1",
        "part": "Pilot lamp",
        "value": "6.3 V",
        "role": "Panel pilot lamp"
      },
      {
        "ref": "JSPK1",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Speaker output"
      },
      {
        "ref": "JSPK2",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Speaker output (second)"
      }
    ]
  },
  "publishedVoltages": {
    "source": "JMI drawing OA/031, 'VOX AC.15 amplifier circuit No. 3', 29-4-60 — working voltages annotated beside the circuit: +325 V reservoir, +315 V rail, +90 V EF86 anode, +220 V phase-inverter anode, +310 V EL84 anodes. No tabulated valve-voltage chart is printed. Cross-checked against the same figures on a published redrawn AC15 schematic (see the sources cited on this page).",
    "nodes": {
      "BPN": {
        "chart": null,
        "note": "Normal-channel supply node, after the 22 kΩ dropper from the +315 V rail (8 µF smoothed)"
      },
      "BPPI": {
        "chart": null,
        "note": "phase-inverter supply node, after its own 22 kΩ dropper from the +315 V rail (8 µF smoothed)"
      },
      "PEF": {
        "chart": 90,
        "tol_pct": 20,
        "note": "EF86 anode — 220 kΩ load. Simulation runs about a quarter low against the printed +90 V; the verification note below explains why the gap sits in the tube model rather than the circuit"
      },
      "SEF": {
        "chart": null,
        "note": "EF86 screen grid, fed through 1 MΩ and bypassed by 0.1 µF — the pentode's gain-setting node"
      },
      "KEF": {
        "chart": null,
        "note": "EF86 cathode (2.2 kΩ, 25 µF bypass)"
      },
      "PPIA": {
        "chart": 220,
        "tol_pct": 20,
        "note": "phase-inverter anode, Normal-channel side (100 kΩ load)"
      },
      "PPIB": {
        "chart": 220,
        "tol_pct": 20,
        "note": "phase-inverter anode, Vibrato/Tremolo side (100 kΩ load) — the drawing prints one figure for the pair"
      },
      "KPI": {
        "chart": null,
        "note": "phase-inverter shared cathode, above the 1.2 kΩ resistor"
      },
      "JPI": {
        "chart": null,
        "note": "tail junction over the 47 kΩ tail — the return for both 1 MΩ grid leaks"
      },
      "S3": {
        "chart": null,
        "note": "EL84 screen grid, through its 100 Ω stopper from the rail"
      },
      "S4": {
        "chart": null,
        "note": "EL84 screen grid, through its 100 Ω stopper from the rail"
      },
      "KOUT": {
        "chart": null,
        "note": "shared EL84 cathode over the single 130 Ω resistor (50 µF bypass) — the amp's entire bias arrangement"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BPN",
      "chart": null,
      "sim": 289.109,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "Normal-channel supply node, after the 22 kΩ dropper from the +315 V rail (8 µF smoothed)",
      "dispute_note": ""
    },
    {
      "node": "BPPI",
      "chart": null,
      "sim": 287.014,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-inverter supply node, after its own 22 kΩ dropper from the +315 V rail (8 µF smoothed)",
      "dispute_note": ""
    },
    {
      "node": "PEF",
      "chart": 90,
      "sim": 66.35,
      "disputed": false,
      "dev_pct": 26.277777777777782,
      "tol_pct": 20,
      "gated": true,
      "within": false,
      "note": "EF86 anode — 220 kΩ load. Simulation runs about a quarter low against the printed +90 V; the verification note below explains why the gap sits in the tube model rather than the circuit",
      "dispute_note": ""
    },
    {
      "node": "SEF",
      "chart": null,
      "sim": 124.764,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EF86 screen grid, fed through 1 MΩ and bypassed by 0.1 µF — the pentode's gain-setting node",
      "dispute_note": ""
    },
    {
      "node": "KEF",
      "chart": null,
      "sim": 2.589,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EF86 cathode (2.2 kΩ, 25 µF bypass)",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 220,
      "sim": 223.41,
      "disputed": false,
      "dev_pct": 1.5499999999999985,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter anode, Normal-channel side (100 kΩ load)",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 220,
      "sim": 223.41,
      "disputed": false,
      "dev_pct": 1.5499999999999985,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter anode, Vibrato/Tremolo side (100 kΩ load) — the drawing prints one figure for the pair",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": null,
      "sim": 61.315,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-inverter shared cathode, above the 1.2 kΩ resistor",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": null,
      "sim": 59.788,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "tail junction over the 47 kΩ tail — the return for both 1 MΩ grid leaks",
      "dispute_note": ""
    },
    {
      "node": "S3",
      "chart": null,
      "sim": 314.594,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid, through its 100 Ω stopper from the rail",
      "dispute_note": ""
    },
    {
      "node": "S4",
      "chart": null,
      "sim": 314.594,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid, through its 100 Ω stopper from the rail",
      "dispute_note": ""
    },
    {
      "node": "KOUT",
      "chart": null,
      "sim": 11.184,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "shared EL84 cathode over the single 130 Ω resistor (50 µF bypass) — the amp's entire bias arrangement",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Outside target",
      "summary": "1 of 3 reference nodes falls outside its stated tolerance.",
      "details": [
        "This compares simulated DC conditions with the cited reference. It does not test sound, physical construction or every part of the circuit."
      ],
      "tone": "attention"
    },
    {
      "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.",
        "15 sheet-only parts are explicitly excluded: CBR, CF3, CKV1, CVC, F1, RD3, RG2, RGS2, RGV, RIN1, RIN2, RIN3, RIN4, RKV1, RKV2. 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 V2, V5, V6, V7.",
        "JMI published no board-layout sheet for the AC15 and none was located; this board is the Circuit Codex's own arrangement, so no factory drawing can establish its heater legs."
      ],
      "tone": "attention"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Checked",
      "summary": "6 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": [],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/ac15"
}