{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "ac30",
  "url": "https://circuitcodex.com/amps/ac30/",
  "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": "ac30",
    "name_style": "Vox AC30/6-style",
    "family": "vox",
    "era": {
      "start": 1961,
      "end": 1965
    },
    "wattage": 30,
    "tubes": [
      "ECC83",
      "ECC83",
      "EL84",
      "EL84",
      "EL84",
      "EL84",
      "ECC83",
      "ECC82",
      "ECC83",
      "GZ34"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "GZ34"
      },
      "bias": "cathode",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "top-cut"
    },
    "lineage": {
      "derived_from": [
        "ac15"
      ],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "JMI factory drawing OS/065 — title block reads 'DRG. Nº OS/065 / THE JENNINGS MUSICAL INDUSTRIES LTD. / \"VOX\" A.C.30.36 AMPLIFIER CIRCUIT / NORMAL / DRAWING FOR WORKS USE ONLY / SCALE:- N/A. DATE 29-4-60. / DRAWN. R.D. TRACED - D.W.U.', with a MODIFICATIONS box reading 'C41 ADDED 7-2-61', then the main list (R4 was 2.2K, R5 was 100K, R6 was 100Ω, R7 was 270K, R9 was 270K, R38 was 1MΩ, R39 was 150K, R40 was 12K, R68 was 1.5MΩ, R64 was 1MΩ, R74 added, C2/C5/C6/C7/C9 changed, C16 deleted, C41 changed) dated 8-5-61, then 'ISS.2 14.6.63 M.T. NOTE ADDED', 'R74 DELETED / R64 WAS 80Ω / FUSE MOD. / 230V WAS 285V' at 'ISS.3 11.10.63' with 'TITLE CHANGED, NORMAL ADDED', and 'ISS.4 11-9-64'. THIS is the revision documented here — the AC30/6 'Normal' circuit as the sheet stands after Issue 4, i.e. the post-'list of changes' amplifier in which one ECC83 replaced the EF86 across the Brilliant and Normal channels. Values read directly from the drawing where its published scan resolves them: V1 ECC83 on two 220 kΩ anode loads (R5, R6) with ONE shared 1.5 kΩ cathode resistor (R4) and a 25 µF bypass (C1), 68 kΩ input resistors (R1, R2, R12, R13) and 1 MΩ leaks (R3, R14); 500 kΩ log volumes (VR1 Normal, VR2 Brilliant) mixing into the V2a grid through 220 kΩ resistors (R7, R9); V2 ECC83 long-tailed pair on 100 kΩ anode loads (R18, R19) with a 1.2 kΩ shared cathode (R16) over a 47 kΩ tail (R15) and 1 MΩ grid leaks (R8, R17) returned to the tail junction; Cut control VR3 250 kΩ log in series with C10 0.0047 µF bridged across the two inverter outputs, with grid-drive returns R20 220 kΩ and R21 280 kΩ; four EL84s (V3-V6) on 1.5 kΩ grid stoppers (R22, R23, R27, R28) and 100 Ω screen stoppers (R25, R26, R29, R30) off the same rail as the anodes, sharing ONE 50 Ω cathode resistor (R24) bypassed by 250 µF · 25 V (C11); two 22 kΩ rail droppers (R10, R11) each with an 8 µF can (C4, C8); GZ34 rectifier (V10) off a 280-0-280 V 160 mA secondary into a 10-20 H 100 mA choke (CH.1) and two 16 µF · 450 V cans; output transformer T1 at 4 kΩ anode-to-anode with 8 Ω and 15 Ω taps; annotated working voltages +320 V rail, +290 V front-end anode supply, +170 V at each V1 anode, +1.6 V at V1's cathode, +230 V at each inverter anode, +55 V at the inverter tail junction, and 'QUIESCENT 10v / 12.5v AT 30 WATTS' at the EL84 cathode resistor. The blue 'NEG FEED BACK' loop drawn across this copy is a later hand addition by a previous owner, not part of the circuit, and is not modelled. Not reproduced here; archived at the Vox AC30 history site.",
        "url": "https://www.voxac30.org.uk/vox_ac30_circuit_diagrams.html"
      },
      {
        "desc": "Vox AC30 history archive, 'Vox AC30/6 circuit diagrams (schematics) 1960-1974' — the identity and dating evidence for the sheet: the circuit 'was initially drawn on the 29th April 1960 by Dick Denney (RD) and traced ... by Derek Underdown (DWU)'; at least six iterations of the AC30/6 'Normal' diagram exist, one of 1960 with no list of changes, one of late 1961/early 1962, two of mid 1963 (one designated A/026), and two of September 1964 (OS/065 and A/026); 'The latest date generally given on sheets numbered as OS/065 ... is 11th September 1964'; the issue history is given as first change 7 February 1960, main list of changes 8 May 1961, ISSUE 2 14 June 1963, ISSUE 3 11 October 1963, ISSUE 4 11 September 1964, '11th Sept. 1964 is the date on or after which the modifications were incorporated in the main circuit'. The same page notes that this copy's values 'are good and legible, except in one instance, which has been supplied in red' and that 'Someone has added a potential negative feedback loop!'",
        "url": "https://www.voxac30.org.uk/vox_ac30_circuit_diagrams.html"
      },
      {
        "desc": "Vox AC30 history archive, 'The Vox AC30/6, black control panels' — what separates this circuit from the AC30/4 and from the AC15: the EF86 replaced by an ECC83, 'one half each for the first stage of the Brilliant and Normal channel', a single treble 'cut' control instead of per-channel tone controls, and the addition of the Brilliant channel; changes introduced in the May 1961 list served 'to lift the gain of the amplifier (Brilliant channel in particular) and to enhance its treble response'; transformers by Haddon Transformers Ltd of South Ruislip and the choke by Radiospares, as on the AC15",
        "url": "https://www.voxac30.org.uk/vox_ac30_6_black_panels.html"
      },
      {
        "desc": "Published Vox factory and service schematics for the later AC30 (el34world's Vox folder, a five-sheet set: AC30 Reverb 1978, AC30 Silver Jubilee, AC30 S.S. Red, AC30 Top Boost Reissue 1994, AC30 Twin Reverb with modifications) — the legibility cross-reference. None of them is a period JMI sheet, so none is used for a value here; they earn their place because the Silver Jubilee sheet carries the SAME inverter and output section, part for part, and resolves the one glyph OS/065 leaves ambiguous. Its long-tailed pair is drawn with 100 kΩ anode loads (R58, R63), a 1 kΩ2 shared cathode, a 47 kΩ tail and 1 MΩ leaks, a 250 kΩ log CUT in series with 47 n across the inverter outputs, four EL84s on 1 kΩ5 grid stoppers and 100 Ω screen stoppers, and a shared cathode resistor bypassed by 250 µF · 25 V — so the AC30/6's R19, whose multiplier glyph on the OS/065 copy reads like an ohm sign, is 100 kΩ. The AC30 Twin Reverb sheet independently shows the 5AR4/GZ34 rectifier and the 4 kΩ anode-to-anode output transformer",
        "url": "https://el34world.com/charts/Schematics/files/Vox/Vox_ac30.pdf"
      },
      {
        "desc": "Independent published circuit analysis of a later Vox AC30 output stage — a third reading of the arrangement this entry documents: four EL84s in parallel push-pull, cathode-biased on a single shared resistor with no bias supply, a DC grid bias of about -10 V, and a 4 kΩ plate-to-plate output transformer; and of the shared first stage, 220 kΩ anode load with a 1.5 kΩ shared cathode resistor, 25 µF bypass and about -1.6 V of bias. Both figures agree with the annotations on OS/065",
        "url": "https://www.ampbooks.com/mobile/classic-circuits/vox-ac30/"
      },
      {
        "desc": "Wikipedia, 'Vox AC30' — the AC30/6's three channels, and Vox swapping 'the Normal channel's EF86 preamp valve for the more common ECC83 (12AX7)' over microphony at higher volume; the AC30/4 and AC30/6 schematics 'both originally dated April 29, 1960'",
        "url": "https://en.wikipedia.org/wiki/Vox_AC30"
      },
      {
        "desc": "Philips/Mullard EL84 data sheet, January 1969 (A.F. Output Pentode) — the datasheet anchor behind the corpus's CC0 EL84 model, which this netlist's four output valves use: 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": "RCA 12AX7-A data sheet (October 1960), 'Characteristics, Class A1 Amplifier' — a readable copy of the 12AX7 average characteristics that anchor the corpus's CC0 12AX7 model, which this netlist's first stage and phase inverter use: Va=250 V / Vg=-2 V -> 1.2 mA at 1600 µmho, second point Va=100 V / Vg=-1 V -> 0.5 mA, mu=100. The model's stated anchor is RCA's Receiving Tube Manual RC-19 (1959), a printed book with no archived scan; this RCA sheet prints the same two points, so it is what a reader can actually open and check. (The URL this entry carried until 2026-09-09 has 404'd.)",
        "url": "https://frank.pocnet.net/sheets/049/1/12AX7A.pdf"
      }
    ],
    "verification": {
      "status": "draft"
    },
    "added": "2026-08-08T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ],
    "sections": {
      "V7": "excluded — the Vibrato/Tremolo channel's first stage, left out with the whole channel: its dropper chain does not resolve back to a named rail on the available scan",
      "V8": "excluded — the Vibrato/Tremolo modulator, left out with the whole channel (see V7)",
      "V9": "excluded — the Vibrato/Tremolo phase-shift oscillator: a running oscillator has no static operating point"
    }
  },
  "parts": {
    "notes": "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, and the parts whose interconnection the published scan does not resolve carry no designator. The blue negative-feedback loop drawn across this copy is a later hand addition by a previous owner and is not a part of this circuit. Two capacitor values on the sheet were silently modernised between issues — the 1961/62 printing specifies 0.05 and 0.005 µF where later sheets, this one included, print 0.047 and 0.0047 µF for the same parts; the values recorded here are the ones OS/065 letters.",
    "items": [
      {
        "ref": "J1",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Brilliant channel input 2"
      },
      {
        "ref": "J2",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Brilliant channel input 1"
      },
      {
        "ref": "R1",
        "part": "Carbon comp resistor",
        "value": "68 kΩ",
        "role": "Brilliant channel input grid stopper (J1)"
      },
      {
        "ref": "R2",
        "part": "Carbon comp resistor",
        "value": "68 kΩ",
        "role": "Brilliant channel input grid stopper (J2)"
      },
      {
        "ref": "R3",
        "part": "Carbon comp resistor",
        "value": "1 MΩ",
        "role": "Brilliant channel input grid leak"
      },
      {
        "ref": "J3",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Normal channel input 2"
      },
      {
        "ref": "J4",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Normal channel input 1"
      },
      {
        "ref": "R12",
        "part": "Carbon comp resistor",
        "value": "68 kΩ",
        "role": "Normal channel input grid stopper (J3)"
      },
      {
        "ref": "R13",
        "part": "Carbon comp resistor",
        "value": "68 kΩ",
        "role": "Normal channel input grid stopper (J4)"
      },
      {
        "ref": "R14",
        "part": "Carbon comp resistor",
        "value": "1 MΩ",
        "role": "Normal channel input grid leak"
      },
      {
        "ref": "J5",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Vibrato/Tremolo channel input 2"
      },
      {
        "ref": "J6",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Vibrato/Tremolo channel input 1"
      },
      {
        "ref": "R10",
        "part": "Power resistor",
        "value": "22 kΩ",
        "role": "Rail dropper, +320 V → front-end anode supply (printed +290 V)"
      },
      {
        "ref": "C4",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Front-end anode supply smoothing"
      },
      {
        "ref": "R5",
        "part": "Carbon comp resistor",
        "value": "220 kΩ",
        "role": "V1 anode load, Brilliant side (pin 1)"
      },
      {
        "ref": "R6",
        "part": "Carbon comp resistor",
        "value": "220 kΩ",
        "role": "V1 anode load, Normal side (pin 6)"
      },
      {
        "ref": "R4",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ",
        "role": "SHARED V1 cathode bias resistor — one network for both channels' first stages (pins 3 and 8 tied)"
      },
      {
        "ref": "C1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V1 shared cathode bypass"
      },
      {
        "ref": "C3",
        "part": "Mica capacitor",
        "value": "500 pF",
        "role": "V1 Brilliant anode → Brilliant volume — the small coupler that gives the channel its name"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "V1 Normal anode → Normal volume"
      },
      {
        "ref": "VR2",
        "part": "Log potentiometer",
        "value": "500 kΩ",
        "role": "Brilliant channel volume"
      },
      {
        "ref": "VR1",
        "part": "Log potentiometer",
        "value": "500 kΩ",
        "role": "Normal channel volume"
      },
      {
        "ref": "R9",
        "part": "Carbon comp resistor",
        "value": "220 kΩ",
        "role": "Brilliant volume wiper → phase-inverter mixing node"
      },
      {
        "ref": "R7",
        "part": "Carbon comp resistor",
        "value": "220 kΩ",
        "role": "Normal volume wiper → phase-inverter mixing node"
      },
      {
        "ref": "C5",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "Mixing node → phase-inverter grid, side A"
      },
      {
        "ref": "R11",
        "part": "Power resistor",
        "value": "22 kΩ",
        "role": "Rail dropper, +320 V → phase-inverter supply"
      },
      {
        "ref": "C8",
        "part": "Electrolytic capacitor",
        "value": "8 µF",
        "role": "Phase-inverter supply smoothing"
      },
      {
        "ref": "R18",
        "part": "Carbon comp resistor",
        "value": "100 kΩ",
        "role": "Phase-inverter anode load, side A (Brilliant + Normal)"
      },
      {
        "ref": "R19",
        "part": "Carbon comp resistor",
        "value": "100 kΩ",
        "role": "Phase-inverter anode load, side B (Vibrato/Tremolo) — the one value whose multiplier glyph this copy leaves ambiguous; see the circuit story"
      },
      {
        "ref": "R8",
        "part": "Carbon comp resistor",
        "value": "1 MΩ",
        "role": "Phase-inverter grid leak, side A, returned to the tail junction"
      },
      {
        "ref": "R17",
        "part": "Carbon comp resistor",
        "value": "1 MΩ",
        "role": "Phase-inverter grid leak, side B, returned to the tail junction"
      },
      {
        "ref": "R16",
        "part": "Carbon comp resistor",
        "value": "1.2 kΩ",
        "role": "Phase-inverter shared cathode resistor"
      },
      {
        "ref": "R15",
        "part": "Carbon comp resistor",
        "value": "47 kΩ",
        "role": "Phase-inverter tail (junction → ground)"
      },
      {
        "ref": "VR4",
        "part": "Log potentiometer",
        "value": "500 kΩ",
        "role": "Vibrato/Tremolo channel volume — feeds the inverter's other grid"
      },
      {
        "ref": "C7",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "Vibrato/Tremolo volume wiper → phase-inverter grid, side B"
      },
      {
        "ref": "VR3",
        "part": "Log potentiometer",
        "value": "250 kΩ",
        "role": "Cut — in series with C10 across the two phase-inverter outputs"
      },
      {
        "ref": "C10",
        "part": "Film capacitor",
        "value": "0.0047 µF",
        "role": "Cut capacitor"
      },
      {
        "ref": "C6",
        "part": "Coupling capacitor",
        "value": "0.15 µF",
        "role": "Phase-inverter anode A → EL84 grid-drive line A (V3 + V5)"
      },
      {
        "ref": "C9",
        "part": "Coupling capacitor",
        "value": "0.15 µF",
        "role": "Phase-inverter anode B → EL84 grid-drive line B (V4 + V6)"
      },
      {
        "ref": "R20",
        "part": "Carbon comp resistor",
        "value": "220 kΩ",
        "role": "EL84 grid-drive line A return to ground — the grid leak for V3 and V5"
      },
      {
        "ref": "R21",
        "part": "Carbon comp resistor",
        "value": "280 kΩ",
        "role": "EL84 grid-drive line B return to ground — the grid leak for V4 and V6, and the drawing's asymmetric partner to R20"
      },
      {
        "ref": "R22",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ",
        "role": "EL84 grid stopper (V3)"
      },
      {
        "ref": "R27",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ",
        "role": "EL84 grid stopper (V5)"
      },
      {
        "ref": "R23",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ",
        "role": "EL84 grid stopper (V4)"
      },
      {
        "ref": "R28",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ",
        "role": "EL84 grid stopper (V6)"
      },
      {
        "ref": "R25",
        "part": "Power resistor",
        "value": "100 Ω",
        "role": "EL84 screen-grid stopper (V3)"
      },
      {
        "ref": "R29",
        "part": "Power resistor",
        "value": "100 Ω",
        "role": "EL84 screen-grid stopper (V5)"
      },
      {
        "ref": "R26",
        "part": "Power resistor",
        "value": "100 Ω",
        "role": "EL84 screen-grid stopper (V4)"
      },
      {
        "ref": "R30",
        "part": "Power resistor",
        "value": "100 Ω",
        "role": "EL84 screen-grid stopper (V6)"
      },
      {
        "ref": "R24",
        "part": "Power resistor",
        "value": "50 Ω",
        "role": "SHARED EL84 cathode bias resistor — the whole bias arrangement for FOUR valves. The drawing annotates it 'QUIESCENT 10v / 12.5v AT 30 WATTS'"
      },
      {
        "ref": "C11",
        "part": "Electrolytic capacitor",
        "value": "250 µF · 25 V",
        "role": "EL84 shared cathode bypass"
      },
      {
        "ref": "R40",
        "part": "Carbon comp resistor",
        "value": "15 kΩ",
        "role": "Vibrato/Tremolo supply dropper"
      },
      {
        "ref": "C19",
        "part": "Electrolytic capacitor",
        "value": "32 µF",
        "role": "Vibrato/Tremolo supply smoothing"
      },
      {
        "ref": "R41",
        "part": "Carbon comp resistor",
        "value": "47 kΩ",
        "role": "Vibrato/Tremolo modulator anode network"
      },
      {
        "ref": "C41",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Vibrato/Tremolo modulator network — the capacitor the 7-2-61 modification added"
      },
      {
        "ref": "R42",
        "part": "Carbon comp resistor",
        "value": "22 kΩ",
        "role": "Vibrato/Tremolo modulator network"
      },
      {
        "ref": "R43",
        "part": "Carbon comp resistor",
        "value": "10 kΩ",
        "role": "Vibrato/Tremolo modulator anode load (V8, one section)"
      },
      {
        "ref": "R44",
        "part": "Carbon comp resistor",
        "value": "10 kΩ",
        "role": "Vibrato/Tremolo modulator anode load (V8, other section)"
      },
      {
        "ref": "—",
        "part": "Tone network",
        "value": "switched capacitor network with 1 MΩ returns",
        "role": "Vibrato/Tremolo channel voicing network ahead of the phase-shift ladder (annotation only)"
      },
      {
        "ref": "—",
        "part": "Phase-shift ladder",
        "value": "capacitor ladder with 1 MΩ returns",
        "role": "The vibrato phase-shift chain feeding the Vibrato/Tremolo volume (annotation only)"
      },
      {
        "ref": "—",
        "part": "Modulator network",
        "value": "resistor/capacitor network around V8",
        "role": "ECC82 modulator around the phase-shift ladder (annotation only)"
      },
      {
        "ref": "—",
        "part": "Oscillator network",
        "value": "three-section RC phase-shift network around V9",
        "role": "ECC83 phase-shift oscillator — the vibrato/tremolo generator (annotation only)"
      },
      {
        "ref": "—",
        "part": "Potentiometer",
        "value": "500 kΩ",
        "role": "Depth preset (annotation only)"
      },
      {
        "ref": "—",
        "part": "Potentiometer",
        "value": "2 MΩ",
        "role": "Vibrato/Tremolo Speed (annotation only)"
      },
      {
        "ref": "—",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Vibrato/Tremolo select (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": "—",
        "part": "Pilot lamp",
        "value": "not drawn",
        "role": "None on the cited drawing: OS/065 (read at 3600 x 2492) draws no pilot lamp anywhere — the mains transformer's 6.3 V winding is arrowed TO VALVE HEATERS with nothing else across it, and the mains input carries only the on/off switch and the 3 A fuse — so none is drawn on the board (annotation only)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Brilliant and Normal first stages — one half each, on a shared cathode network"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Long-tailed-pair phase inverter — all three channels mix here"
      },
      {
        "ref": "V3",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output, side A (upper)"
      },
      {
        "ref": "V5",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output, side A (parallel with V3)"
      },
      {
        "ref": "V4",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output, side B (lower)"
      },
      {
        "ref": "V6",
        "part": "Power tube",
        "value": "EL84",
        "role": "Push-pull output, side B (parallel with V4)"
      },
      {
        "ref": "V7",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Vibrato/Tremolo channel first stage"
      },
      {
        "ref": "V8",
        "part": "Preamp tube",
        "value": "ECC82 (12AU7)",
        "role": "Vibrato/Tremolo modulator"
      },
      {
        "ref": "V9",
        "part": "Preamp tube",
        "value": "ECC83 (12AX7)",
        "role": "Vibrato/Tremolo phase-shift oscillator"
      },
      {
        "ref": "V10",
        "part": "Rectifier tube",
        "value": "GZ34 (5AR4)",
        "role": "Full-wave rectifier"
      },
      {
        "ref": "T2",
        "part": "Power transformer",
        "value": "HT secondary 280-0-280 V at 160 mA · 6.3 V, 6 A heater winding · 5 V, 2 A rectifier winding · primary taps 115/160/205/225/245 V",
        "role": "Mains/HT transformer (Haddon)"
      },
      {
        "ref": "T1",
        "part": "Output transformer",
        "value": "4 kΩ anode-to-anode primary · 8 Ω / 15 Ω secondary taps",
        "role": "Output transformer (Haddon)"
      },
      {
        "ref": "CH1",
        "part": "Filter choke",
        "value": "10–20 H · 100 mA DC",
        "role": "Smoothing choke between reservoir and HT rail (Radiospares)"
      },
      {
        "ref": "C39",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Reservoir filter, GZ34 cathode side"
      },
      {
        "ref": "C40",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Smoothing filter after the choke"
      },
      {
        "ref": "F1",
        "part": "Fuse",
        "value": "3 A",
        "role": "Mains fuse"
      },
      {
        "ref": "SW4",
        "part": "Toggle switch",
        "value": "DPST",
        "role": "Mains on/off"
      },
      {
        "ref": "SW3",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Vibrato/Tremolo on/off, panel"
      },
      {
        "ref": "QS",
        "part": "Mains socket",
        "value": "3-pin",
        "role": "Mains input socket"
      },
      {
        "ref": "JSPK1",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Speaker output"
      }
    ]
  },
  "publishedVoltages": {
    "source": "JMI drawing OS/065, 'VOX A.C.30.36 AMPLIFIER CIRCUIT / NORMAL', title-block date 29-4-60, modifications through ISS.4 of 11-9-64 — working voltages annotated beside the circuit: +320 V rail, +290 V front-end anode supply, +170 V V1 anodes, +1.6 V V1 cathode, +230 V phase-inverter anodes, '565v' (56.5 V; the decimal point is not visible) at the inverter's joined cathodes, +55 V inverter tail junction, and 'QUIESCENT 10v / 12.5v AT 30 WATTS' at the shared EL84 cathode resistor. No tabulated valve-voltage chart is printed and no measurement convention is stated.",
    "nodes": {
      "BPN": {
        "chart": 290,
        "tol_pct": 20,
        "note": "front-end anode supply, after the 22 kΩ dropper R10 from the +320 V rail (8 µF C4). Simulated slightly high by construction: any current the excluded Vibrato/Tremolo chain draws from this side of the supply is not modelled"
      },
      "PV1A": {
        "chart": 170,
        "tol_pct": 20,
        "note": "V1 Brilliant-channel anode (pin 1), 220 kΩ load R5"
      },
      "PV1B": {
        "chart": 170,
        "tol_pct": 20,
        "note": "V1 Normal-channel anode (pin 6), 220 kΩ load R6 — the drawing prints the same figure at both anodes"
      },
      "KV1": {
        "chart": 1.6,
        "tol_pct": 20,
        "note": "V1's SHARED cathode (pins 3 and 8 tied), 1.5 kΩ R4 with a 25 µF bypass — one bias network for both channels' first stages, which is why neither half can be solved alone"
      },
      "BPPI": {
        "chart": null,
        "note": "phase-inverter supply node, after its own 22 kΩ dropper R11 from the +320 V rail (8 µF C8) — the drawing annotates the anodes, not this node"
      },
      "PPIA": {
        "chart": 230,
        "tol_pct": 20,
        "note": "phase-inverter anode, Brilliant/Normal side (100 kΩ load R18). Annotation revised from 285 V at ISS.3, 11-10-63"
      },
      "PPIB": {
        "chart": 230,
        "tol_pct": 20,
        "note": "phase-inverter anode, Vibrato/Tremolo side (100 kΩ load R19) — the drawing prints one figure for the pair. R19's multiplier glyph is the one value on this copy that does not resolve cleanly; see the circuit story"
      },
      "KPI": {
        "chart": 56.5,
        "tol_pct": 20,
        "note": "phase-inverter joined cathodes (V2 pins 3/8), above the 1.2 kΩ R16 — OS/065 letters '565v' there with no decimal point visible; 565 V would stand above the +320 V rail, so the figure is 56.5 V, a volt and a half above the +55 V the sheet prints at the tail junction below R16"
      },
      "JPI": {
        "chart": 55,
        "tol_pct": 20,
        "note": "tail junction over the 47 kΩ R15 — the return for both 1 MΩ grid leaks, and the drawing's one annotated figure inside the inverter's cathode circuit"
      },
      "NGA": {
        "chart": null,
        "note": "EL84 grid-drive line, side A (V3 + V5), returned to ground through R20 220 kΩ — 0 V by construction"
      },
      "NGB": {
        "chart": null,
        "note": "EL84 grid-drive line, side B (V4 + V6), returned to ground through R21 280 kΩ — the drawing's asymmetric partner to R20"
      },
      "S3": {
        "chart": null,
        "note": "EL84 screen grid (V3), through its 100 Ω stopper R25 from the rail"
      },
      "S4": {
        "chart": null,
        "note": "EL84 screen grid (V4), through its 100 Ω stopper R26"
      },
      "S5": {
        "chart": null,
        "note": "EL84 screen grid (V5), through its 100 Ω stopper R29"
      },
      "S6": {
        "chart": null,
        "note": "EL84 screen grid (V6), through its 100 Ω stopper R30"
      },
      "KOUT": {
        "chart": 10,
        "tol_pct": 20,
        "note": "shared EL84 cathode over the single 50 Ω R24 (250 µF bypass) — the amp's entire bias arrangement for four valves. The drawing's 'QUIESCENT 10v' works out at 200 mA of cathode current for the quad, 50 mA a valve"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BPN",
      "chart": 290,
      "sim": 295.347,
      "disputed": false,
      "dev_pct": 1.8437931034482689,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "front-end anode supply, after the 22 kΩ dropper R10 from the +320 V rail (8 µF C4). Simulated slightly high by construction: any current the excluded Vibrato/Tremolo chain draws from this side of the supply is not modelled",
      "dispute_note": ""
    },
    {
      "node": "PV1A",
      "chart": 170,
      "sim": 172.081,
      "disputed": false,
      "dev_pct": 1.224117647058817,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V1 Brilliant-channel anode (pin 1), 220 kΩ load R5",
      "dispute_note": ""
    },
    {
      "node": "PV1B",
      "chart": 170,
      "sim": 172.081,
      "disputed": false,
      "dev_pct": 1.224117647058817,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V1 Normal-channel anode (pin 6), 220 kΩ load R6 — the drawing prints the same figure at both anodes",
      "dispute_note": ""
    },
    {
      "node": "KV1",
      "chart": 1.6,
      "sim": 1.681,
      "disputed": false,
      "dev_pct": 5.062499999999997,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V1's SHARED cathode (pins 3 and 8 tied), 1.5 kΩ R4 with a 25 µF bypass — one bias network for both channels' first stages, which is why neither half can be solved alone",
      "dispute_note": ""
    },
    {
      "node": "BPPI",
      "chart": null,
      "sim": 291.626,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "phase-inverter supply node, after its own 22 kΩ dropper R11 from the +320 V rail (8 µF C8) — the drawing annotates the anodes, not this node",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 230,
      "sim": 227.14,
      "disputed": false,
      "dev_pct": 1.2434782608695711,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter anode, Brilliant/Normal side (100 kΩ load R18). Annotation revised from 285 V at ISS.3, 11-10-63",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 230,
      "sim": 227.14,
      "disputed": false,
      "dev_pct": 1.2434782608695711,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter anode, Vibrato/Tremolo side (100 kΩ load R19) — the drawing prints one figure for the pair. R19's multiplier glyph is the one value on this copy that does not resolve cleanly; see the circuit story",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 56.5,
      "sim": 62.165,
      "disputed": false,
      "dev_pct": 10.026548672566369,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "phase-inverter joined cathodes (V2 pins 3/8), above the 1.2 kΩ R16 — OS/065 letters '565v' there with no decimal point visible; 565 V would stand above the +320 V rail, so the figure is 56.5 V, a volt and a half above the +55 V the sheet prints at the tail junction below R16",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": 55,
      "sim": 60.617,
      "disputed": false,
      "dev_pct": 10.212727272727268,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "tail junction over the 47 kΩ R15 — the return for both 1 MΩ grid leaks, and the drawing's one annotated figure inside the inverter's cathode circuit",
      "dispute_note": ""
    },
    {
      "node": "NGA",
      "chart": null,
      "sim": 0,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 grid-drive line, side A (V3 + V5), returned to ground through R20 220 kΩ — 0 V by construction",
      "dispute_note": ""
    },
    {
      "node": "NGB",
      "chart": null,
      "sim": 0,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 grid-drive line, side B (V4 + V6), returned to ground through R21 280 kΩ — the drawing's asymmetric partner to R20",
      "dispute_note": ""
    },
    {
      "node": "S3",
      "chart": null,
      "sim": 319.482,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid (V3), through its 100 Ω stopper R25 from the rail",
      "dispute_note": ""
    },
    {
      "node": "S4",
      "chart": null,
      "sim": 319.482,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid (V4), through its 100 Ω stopper R26",
      "dispute_note": ""
    },
    {
      "node": "S5",
      "chart": null,
      "sim": 319.482,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid (V5), through its 100 Ω stopper R29",
      "dispute_note": ""
    },
    {
      "node": "S6",
      "chart": null,
      "sim": 319.482,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "EL84 screen grid (V6), through its 100 Ω stopper R30",
      "dispute_note": ""
    },
    {
      "node": "KOUT",
      "chart": 10,
      "sim": 10.625,
      "disputed": false,
      "dev_pct": 6.25,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared EL84 cathode over the single 50 Ω R24 (250 µF bypass) — the amp's entire bias arrangement for four valves. The drawing's 'QUIESCENT 10v' works out at 200 mA of cathode current for the quad, 50 mA a valve",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Within target",
      "summary": "9 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: C19, C41, F1, R40, R41, R42, R43, R44. 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, V7, V8, V9.",
        "JMI published no board-layout sheet for the AC30 and none was located; this board is derived from the circuit drawing, so no factory drawing can establish its heater legs.",
        "V1: pins [4, 5] are one leg at 6.3 V and opposite legs at 12.6 V"
      ],
      "tone": "attention"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Checked",
      "summary": "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/ac30"
}