{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "6161",
  "url": "https://circuitcodex.com/amps/6161/",
  "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": "6161",
    "name_style": "Valco 6161-style",
    "family": "other",
    "era": {
      "start": 1960,
      "end": 1968
    },
    "wattage": 14,
    "tubes": [
      "12AX7",
      "12AX7",
      "12AX7",
      6973,
      6973,
      "5Y3GT"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "5Y3GT"
      },
      "bias": "cathode",
      "phase_inverter": "paraphase",
      "tone_stack": "single-knob"
    },
    "lineage": {
      "derived_from": [],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Valco factory drawing, title block 'Valco Model 6161' set vertically along the left edge of the sheet — THIS is the revision documented here. Complement read from the drawing: V1 12AX7 (both channels, one half each), V2 12AX7 (paraphase phase inverter, both halves), V3 12AX7 (tremolo oscillator and its cathode-follower output, both halves), V4 and V5 6973, V6 5Y3-GT. Values read directly from the drawing: 6973 pair on ONE shared 250 Ω cathode resistor with a 35 µF/50 V bypass and no bias supply; screens taken from their own supply node, not from taps on the output-transformer primary; 270 kΩ inverter anode loads with a 270 kΩ/12 kΩ divider feeding the inverted half's grid, 2.2 kΩ (0.05 µF bypassed) and 3.9 kΩ (unbypassed) inverter cathodes; 0.01 µF inverter-to-grid couplers; 470 kΩ grid leak on one output grid, the divider itself on the other; supply chain 20 µF reservoir → 1 kΩ · 1 W → 10 µF screen node → 15 kΩ → 10 µF B1 rail, with a further 100 kΩ dropper and 0.05 µF decoupling per preamp channel; both channels on 270 kΩ plate loads and 470 kΩ grid leaks, channel 1 on an unbypassed 2.2 kΩ cathode and channel 2 on 1.5 kΩ with a 35 µF bypass; each channel fed by a pair of jacks marked Treble and Bass through a 0.005 µF coupler and a 100 kΩ mixing resistor; 500 kΩ volume per channel with a 0.0005 µF bright cap, the two wipers summed through 270 kΩ each into a single 500 kΩ tone control working on 0.005 µF; power transformer E-3693A, output transformer 340-6, two 10-inch 550-3 speakers. The drawing prints NO voltages of any kind. Not reproduced here; archived at el34world's Valco schematic library.",
        "url": "https://el34world.com/charts/Schematics/files/Valco/Valco_6161.pdf"
      },
      {
        "desc": "Published redrawn schematic of the Supro 1624T, captioned 'Supro 1624T' and signed 'Drawn by Ryan@ClassicTubeAmps.com' — the legibility cross-reference and the corroborating second reading. The 1624T is the Supro-badged sibling of this chassis, and the two published drawings agree part for part on the whole supply chain (20 µF / 1 kΩ · 1 W / 10 µF / 15 kΩ / 10 µF), on the shared 250 Ω output cathode resistor and its 35 µF bypass, on the 270 kΩ/12 kΩ paraphase divider and the 470 kΩ leak on the opposite output grid, and on the 2.2 kΩ-bypassed / 3.9 kΩ-unbypassed inverter cathodes. Where the redraw's lettering is ambiguous the FACTORY drawing is the value recorded: the redraw prints the output cathode resistor as '250K 7W', which the Valco drawing gives plainly as 250, and which a published measurement (below) confirms by reading 24 V across it.",
        "url": "https://el34world.com/charts/Schematics/files/Supro/Supro_1624t_schematic_263.pdf"
      },
      {
        "desc": "Published measurement set taken on a 1965 Supro 1624T and posted to The Amp Garage by Stevem, 17 August 2022 — the only voltage reference this entry has, since the drawing prints none. Reported: HT secondary 336 V AC per leg unloaded and 323 V loaded at idle; '6973 plate=369', '6973 screen=350', '6973 grid resistor =250 ohm, idle voltage 24'; preamp readings by socket, 212 V/2.36 V and 118 V/0.980 V on one bottle, 132 V/1.12 V and 173 V/1.6 V on another, 286 V/2.4 V and 219 V/0.680 V on the third; 16 W RMS into 8 Ω at clipping, 19.6 W peak. Used as measurements, never as a chart — see the operating-point table.",
        "url": "https://ampgarage.com/forum/viewtopic.php?t=35643"
      },
      {
        "desc": "Dealer documentation of a 1960 Gretsch 6161 Electromatic Twin at Cream City Music — the earliest dated example this entry can cite for the complement on the drawing: '5Y3, 6973 (2), 12AX7 (3)', rated '14 Watts', controls 'Volume, Tremolo, Tone', and a note that ClassicTone was 'the original OEM transformer manufacturer for Valco/Gretsch in the 50s and 60s'. The Gretsch-badged 6161 is this Valco chassis; the 14 W figure is the period rating recorded in this entry's wattage field.",
        "url": "https://www.creamcitymusic.com/vintage-gretsch-6161-electromatic-twin-14w-1x12-tube-combo-amp-1960/"
      },
      {
        "desc": "Steel Guitar Forum service thread on a 1957 Gretsch 6161 — evidence that the 6161 model number covers more than one circuit, and an independent naming of the inverter. That amp is described as '2 6V6's on the output, 2 6SQ7 triodes (preamp and tremolo) and a 12AX7' phase inverter, with 'later versions' carrying 6973 output tubes; the poster names the inverter arrangement 'paraphase', which is what the drawing documented here also shows. Its 6V6 pair sits on a 330 Ω cathode resistor dropping 21 V at idle — the same one-shared-resistor bias arrangement at a different value.",
        "url": "https://bb.steelguitarforum.com/viewtopic.php?t=354380"
      },
      {
        "desc": "Wikipedia, 'Valco' — the maker chronology behind this entry's era bracket and the new Supro/Valco line history: Valco was established in 1940 by Victor Smith, Al Frost and Louis Dopyera, formerly of the National Dobro Company, the name coming from their initials plus the abbreviation for company; it built instruments and amplifiers under Supro, Airline, National and Oahu and also 'produced amplifiers under contract for Gretsch, Harmony, and Kay'; in 1967 it merged with the Kay Musical Instrument Company and the merged company folded the following year.",
        "url": "https://en.wikipedia.org/wiki/Valco"
      },
      {
        "desc": "RCA 6973 data sheet, 10-60 (Beam Power Tube, 9-pin miniature) — anchor for the CC0 6973 tube model and the ratings that make this output stage what it is: Va=250 V, Vg2=250 V, Vg1=-15 V → Ia=46 mA, Ig2=3.5 mA, gm=4800 µmho; design-maximum 12 W plate dissipation, 2 W screen, 330 V screen, and a separate 410 V ceiling that applies only when the screens are tapped on the output-transformer primary — which this circuit does not do. See the 6973 tube page and this corpus's tube-model methodology.",
        "url": "https://frank.pocnet.net/sheets/049/6/6973.pdf"
      }
    ],
    "verification": {
      "status": "draft"
    },
    "added": "2026-08-08T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ],
    "sections": {
      "V3A": "excluded — the tremolo's phase-shift oscillator: a running oscillator shifted by grid-leak detection has no static operating point; its missing plate current reads B1 and every node below it a few volts high, so those nodes are informational"
    }
  },
  "parts": {
    "notes": "Capacitor values are open at DC and do not enter the operating-point netlist; they are listed for completeness, and the ones whose BOTH leads land on a named DC node are modelled anyway so the push-pull phase and the decoupling placement are fixed in the data. Wattages are the drawing's where it prints them (1000-1W, 250-7W) and the era's implied ½ W elsewhere; the drawing marks no tolerances. The output cathode resistor is the part to get right: a published redraw of the Supro-badged sibling letters it '250K 7W', the factory drawing gives it as 250, and a published measurement reads 24 V across it at idle — 250 Ω is the value, and 250 kΩ would bias the pair off.",
    "items": [
      {
        "ref": "V1",
        "part": "Tube",
        "value": "12AX7",
        "role": "Both preamp channels, one triode each"
      },
      {
        "ref": "V2",
        "part": "Tube",
        "value": "12AX7",
        "role": "Paraphase phase inverter, both triodes"
      },
      {
        "ref": "V3",
        "part": "Tube",
        "value": "12AX7",
        "role": "Tremolo — phase-shift oscillator (V3A, excluded from the netlist) and cathode-follower output (V3B)"
      },
      {
        "ref": "V4",
        "part": "Tube",
        "value": "6973",
        "role": "Output beam power tube"
      },
      {
        "ref": "V5",
        "part": "Tube",
        "value": "6973",
        "role": "Output beam power tube"
      },
      {
        "ref": "V6",
        "part": "Rectifier tube",
        "value": "5Y3GT",
        "role": "Full-wave rectifier"
      },
      {
        "ref": "T1",
        "part": "Power transformer",
        "value": "Valco E-3693A",
        "role": "Mains transformer — centre-tapped HT winding (grounded), 5 V rectifier winding, 6.3 V heater winding. The drawing prints the part number and no winding voltages"
      },
      {
        "ref": "T2",
        "part": "Output transformer",
        "value": "Valco 340-6",
        "role": "Output transformer, centre-tapped primary; the centre tap is the reservoir node"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Channel 1 input, panel-marked Treble"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Channel 1 input, panel-marked Bass"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Channel 2 input, panel-marked Treble"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Channel 2 input, panel-marked Bass"
      },
      {
        "ref": "CIN1",
        "part": "Coupling capacitor",
        "value": "0.005 µF",
        "role": "Channel 1 Treble-jack input coupler — mounts at the jacks"
      },
      {
        "ref": "CIN2",
        "part": "Coupling capacitor",
        "value": "0.005 µF",
        "role": "Channel 2 Treble-jack input coupler — mounts at the jacks"
      },
      {
        "ref": "RMX1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel 1 Bass-jack mixing resistor — mounts at the jacks"
      },
      {
        "ref": "RMX2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel 2 Bass-jack mixing resistor — mounts at the jacks"
      },
      {
        "ref": "RD3",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel 1 supply dropper, B1 → channel 1 node"
      },
      {
        "ref": "CF4",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Channel 1 supply decoupling"
      },
      {
        "ref": "RL1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel 1 plate load"
      },
      {
        "ref": "RG1",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Channel 1 grid leak — straight off the input node, no grid stopper on this channel"
      },
      {
        "ref": "RK1",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Channel 1 cathode bias — UNBYPASSED, no can on this channel"
      },
      {
        "ref": "CV1",
        "part": "Coupling capacitor",
        "value": "0.005 µF",
        "role": "Channel 1 plate → volume coupler"
      },
      {
        "ref": "RD4",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Channel 2 supply dropper, B1 → channel 2 node"
      },
      {
        "ref": "CF5",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Channel 2 supply decoupling"
      },
      {
        "ref": "RL2",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel 2 plate load"
      },
      {
        "ref": "RGS1",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Channel 2 grid stopper"
      },
      {
        "ref": "RG2",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Channel 2 grid leak"
      },
      {
        "ref": "RK2",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "Channel 2 cathode bias — SHARED with the tremolo follower V3B, which is the tremolo mechanism"
      },
      {
        "ref": "CK2",
        "part": "Electrolytic capacitor",
        "value": "35 µF · 50 V",
        "role": "Channel 2 cathode bypass"
      },
      {
        "ref": "CP2",
        "part": "Mica capacitor",
        "value": "500 pF",
        "role": "Channel 2 plate-to-ground treble cut — the cap channel 1 does not have"
      },
      {
        "ref": "CI1",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Channel 2 interstage coupler, first of two in series"
      },
      {
        "ref": "RI1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel 2 interstage shunt to ground, between the two 0.005 µF couplers"
      },
      {
        "ref": "CI2",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Channel 2 interstage coupler, second of two in series"
      },
      {
        "ref": "VR1",
        "part": "Log potentiometer",
        "value": "500 kΩ-A",
        "role": "Channel 1 volume"
      },
      {
        "ref": "CB1",
        "part": "Mica capacitor",
        "value": "500 pF",
        "role": "Bright cap, channel 1 volume top → wiper"
      },
      {
        "ref": "RM1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel 1 mixing resistor, volume wiper → mixer node"
      },
      {
        "ref": "VR2",
        "part": "Log potentiometer",
        "value": "500 kΩ-A",
        "role": "Channel 2 volume"
      },
      {
        "ref": "CB2",
        "part": "Mica capacitor",
        "value": "500 pF",
        "role": "Bright cap, channel 2 volume top → wiper"
      },
      {
        "ref": "RM2",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel 2 mixing resistor, volume wiper → mixer node"
      },
      {
        "ref": "CT1",
        "part": "Mica capacitor",
        "value": "500 pF",
        "role": "Fixed treble shunt, mixer node → ground"
      },
      {
        "ref": "CT2",
        "part": "Film capacitor",
        "value": "0.005 µF",
        "role": "Tone capacitor, mixer node → Tone control"
      },
      {
        "ref": "VR3",
        "part": "Log potentiometer",
        "value": "500 kΩ-A",
        "role": "Tone — the amp's only tone control, shared by both channels; wired as a rheostat with its wiper grounded"
      },
      {
        "ref": "CPI",
        "part": "Mica capacitor",
        "value": "300 pF",
        "role": "Mixer node → inverter driver grid coupler"
      },
      {
        "ref": "RL3",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Inverter driver plate load (V2A)"
      },
      {
        "ref": "RG3",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Inverter driver grid leak"
      },
      {
        "ref": "RK3",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Inverter driver cathode bias"
      },
      {
        "ref": "CK3",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Inverter driver cathode bypass"
      },
      {
        "ref": "RL4",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Inverter inverted-side plate load (V2B)"
      },
      {
        "ref": "RK4",
        "part": "Carbon comp resistor",
        "value": "3.9 kΩ · ½ W",
        "role": "Inverter inverted-side cathode bias — left UNBYPASSED, which is what sets that half's gain"
      },
      {
        "ref": "RPA",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Paraphase divider, upper leg — V5 grid down to the V2B grid tap; doubles as most of V5's grid leak"
      },
      {
        "ref": "RPB",
        "part": "Carbon comp resistor",
        "value": "12 kΩ · ½ W",
        "role": "Paraphase divider, lower leg — the V2B grid tap down to ground"
      },
      {
        "ref": "CC1",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Inverter driver plate → V5 grid"
      },
      {
        "ref": "CC2",
        "part": "Coupling capacitor",
        "value": "0.01 µF",
        "role": "Inverter inverted-side plate → V4 grid"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "V4 grid leak"
      },
      {
        "ref": "RKO",
        "part": "Power resistor",
        "value": "250 Ω · 7 W",
        "role": "SHARED 6973 cathode bias resistor — the whole bias arrangement for the pair, with no bias supply anywhere in the amp"
      },
      {
        "ref": "CKO",
        "part": "Electrolytic capacitor",
        "value": "35 µF · 50 V",
        "role": "6973 cathode bypass"
      },
      {
        "ref": "CF1",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 450 V",
        "role": "Reservoir can — the 6973 plate node and the output-transformer centre tap"
      },
      {
        "ref": "RD1",
        "part": "Power resistor",
        "value": "1 kΩ · 1 W",
        "role": "Reservoir → 6973 screen node"
      },
      {
        "ref": "CF2",
        "part": "Electrolytic capacitor",
        "value": "10 µF · 450 V",
        "role": "6973 screen node smoothing"
      },
      {
        "ref": "RD2",
        "part": "Carbon comp resistor",
        "value": "15 kΩ · ½ W",
        "role": "Screen node → B1, the preamp and inverter rail"
      },
      {
        "ref": "CF3",
        "part": "Electrolytic capacitor",
        "value": "10 µF · 450 V",
        "role": "B1 rail smoothing"
      },
      {
        "ref": "—",
        "part": "Speaker",
        "value": "10 in · 550-3 (×2)",
        "role": "Two 10-inch speakers (annotation only)"
      },
      {
        "ref": "—",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Mains-side capacitor, drawn as C1 across the primary (annotation only)"
      },
      {
        "ref": "—",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Mains on/off, ganged with the line-reverse arrangement (annotation only)"
      },
      {
        "ref": "—",
        "part": "Fuse",
        "value": "2 A",
        "role": "Mains fuse (annotation only)"
      },
      {
        "ref": "—",
        "part": "Neon indicator",
        "value": "neon",
        "role": "Pilot lamp — a neon across the mains side, not a 6.3 V bulb (annotation only)"
      },
      {
        "ref": "RTO1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Tremolo oscillator plate load, taps B1 (oscillator excluded from the netlist)"
      },
      {
        "ref": "RTOK",
        "part": "Carbon comp resistor",
        "value": "1 kΩ · ½ W",
        "role": "Tremolo oscillator cathode bias"
      },
      {
        "ref": "RTOG",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Tremolo oscillator grid stopper"
      },
      {
        "ref": "CTO1",
        "part": "Film capacitor",
        "value": "0.03 µF",
        "role": "Tremolo phase-shift ladder capacitor, plate end"
      },
      {
        "ref": "CTO2",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Tremolo phase-shift ladder capacitor, middle"
      },
      {
        "ref": "CTO3",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Tremolo phase-shift ladder capacitor, grid end"
      },
      {
        "ref": "RTOR1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Tremolo phase-shift ladder return"
      },
      {
        "ref": "RTOR2",
        "part": "Carbon comp resistor",
        "value": "1.5 MΩ · ½ W",
        "role": "Tremolo phase-shift ladder return"
      },
      {
        "ref": "RSPD",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Speed control series resistor"
      },
      {
        "ref": "VR4",
        "part": "Log potentiometer",
        "value": "500 kΩ-A",
        "role": "Tremolo Speed — wired as a rheostat off the ladder's first node"
      },
      {
        "ref": "CTOUT",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Tremolo oscillator output coupler"
      },
      {
        "ref": "RTOUT",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Tremolo output series resistor ahead of the footswitch"
      },
      {
        "ref": "SW1",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "Tremolo on/off, in series with the oscillator output"
      },
      {
        "ref": "—",
        "part": "Jack socket",
        "value": "1/4 in",
        "role": "Footswitch jack (annotation only)"
      },
      {
        "ref": "RTI1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Intensity network, first leg after the footswitch jack"
      },
      {
        "ref": "CTI1",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Intensity network shunt, first node"
      },
      {
        "ref": "RTI2",
        "part": "Carbon comp resistor",
        "value": "1.5 MΩ · ½ W",
        "role": "Intensity network, second leg"
      },
      {
        "ref": "CTI2",
        "part": "Film capacitor",
        "value": "0.05 µF",
        "role": "Intensity network shunt, second node — parallels the follower's 270 kΩ grid return"
      },
      {
        "ref": "RGS2",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Tremolo follower grid stopper"
      },
      {
        "ref": "RTI",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Tremolo follower grid return — the foot of the Intensity network"
      },
      {
        "ref": "—",
        "part": "Toggle switch",
        "value": "SPST",
        "role": "The A–A pair. The drawing brings BOTH output-tube grid nodes out to markers lettered A and resolves them no further; the published redraw of the Supro-badged sibling draws an SPST switch bridging exactly those two nodes, which shorts the grids together and silences the amplifier. Annotation only, and DC-free either way"
      }
    ]
  },
  "publishedVoltages": {
    "source": "No voltages are printed on the Valco 6161 drawing. Reference figures are a published measurement set taken on a 1965 Supro 1624T — the same 3×12AX7 / 2×6973 / 5Y3-GT chassis with an identical supply chain and output stage — reporting 369 V at the 6973 plates (driven here), 350 V at the 6973 screens, and 24 V across the 250 Ω shared cathode resistor. See the sources cited on this page for the link.",
    "nodes": {
      "BP2": {
        "chart": 350,
        "tol_pct": 20,
        "note": "6973 screen node — the 10 µF can after the 1 kΩ · 1 W dropper. This circuit gives its screens their own supply node; it does NOT tap them on the output-transformer primary, which is the other arrangement the 6973 data sheet rates"
      },
      "KOUT": {
        "chart": 24,
        "tol_pct": 20,
        "note": "shared 6973 cathode over the single 250 Ω · 7 W resistor (35 µF bypass) — the amp's entire bias arrangement, for both bottles, with no bias supply anywhere"
      },
      "B1": {
        "chart": null,
        "note": "informational — preamp and inverter rail after the 15 kΩ dropper. Reads high by construction: the excluded tremolo oscillator's 270 kΩ plate load taps this node (see the netlist's scope note)"
      },
      "BC1": {
        "chart": null,
        "note": "informational — channel 1 supply node, after its own 100 kΩ dropper from B1 (0.05 µF decoupling)"
      },
      "BC2": {
        "chart": null,
        "note": "informational — channel 2 supply node, after its own 100 kΩ dropper from B1 (0.05 µF decoupling)"
      },
      "P1A": {
        "chart": null,
        "note": "informational — channel 1 plate, 270 kΩ load over an UNBYPASSED 2.2 kΩ cathode"
      },
      "K1A": {
        "chart": null,
        "note": "informational — channel 1 cathode, 2.2 kΩ with no bypass can"
      },
      "P1B": {
        "chart": null,
        "note": "informational — channel 2 plate, 270 kΩ load"
      },
      "K1B": {
        "chart": null,
        "note": "informational — channel 2 cathode, 1.5 kΩ with a 35 µF bypass. This node carries TWO tubes' cathode current: the tremolo follower V3B lands on it directly, which is why it idles well above a normal 12AX7 cathode and why the tremolo works at all (see the circuit story)"
      },
      "P2A": {
        "chart": null,
        "note": "informational — paraphase driver plate (270 kΩ load), the half that drives V5's grid"
      },
      "K2A": {
        "chart": null,
        "note": "informational — driver cathode, 2.2 kΩ bypassed by 0.05 µF"
      },
      "P2B": {
        "chart": null,
        "note": "informational — paraphase inverted-side plate (270 kΩ load), the half that drives V4's grid"
      },
      "K2B": {
        "chart": null,
        "note": "informational — inverted-side cathode, 3.9 kΩ left UNBYPASSED; that degeneration is what trims this half's gain down to the 23.5× the 270 kΩ/12 kΩ divider asks for"
      },
      "G2B": {
        "chart": null,
        "note": "informational — the paraphase tap itself, where the 270 kΩ from V5's grid meets the 12 kΩ to ground. Idles at exactly 0 V: there is no grid-current model (a stated limitation of the corpus's tube models)"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 350,
      "sim": 359.813,
      "disputed": false,
      "dev_pct": 2.8037142857142823,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "6973 screen node — the 10 µF can after the 1 kΩ · 1 W dropper. This circuit gives its screens their own supply node; it does NOT tap them on the output-transformer primary, which is the other arrangement the 6973 data sheet rates",
      "dispute_note": ""
    },
    {
      "node": "KOUT",
      "chart": 24,
      "sim": 25.137,
      "disputed": false,
      "dev_pct": 4.7375000000000025,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared 6973 cathode over the single 250 Ω · 7 W resistor (35 µF bypass) — the amp's entire bias arrangement, for both bottles, with no bias supply anywhere",
      "dispute_note": ""
    },
    {
      "node": "B1",
      "chart": null,
      "sim": 310.787,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — preamp and inverter rail after the 15 kΩ dropper. Reads high by construction: the excluded tremolo oscillator's 270 kΩ plate load taps this node (see the netlist's scope note)",
      "dispute_note": ""
    },
    {
      "node": "BC1",
      "chart": null,
      "sim": 258.372,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 1 supply node, after its own 100 kΩ dropper from B1 (0.05 µF decoupling)",
      "dispute_note": ""
    },
    {
      "node": "BC2",
      "chart": null,
      "sim": 285.217,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 2 supply node, after its own 100 kΩ dropper from B1 (0.05 µF decoupling)",
      "dispute_note": ""
    },
    {
      "node": "P1A",
      "chart": null,
      "sim": 116.849,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 1 plate, 270 kΩ load over an UNBYPASSED 2.2 kΩ cathode",
      "dispute_note": ""
    },
    {
      "node": "K1A",
      "chart": null,
      "sim": 1.153,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 1 cathode, 2.2 kΩ with no bypass can",
      "dispute_note": ""
    },
    {
      "node": "P1B",
      "chart": null,
      "sim": 216.178,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 2 plate, 270 kΩ load",
      "dispute_note": ""
    },
    {
      "node": "K1B",
      "chart": null,
      "sim": 2.478,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — channel 2 cathode, 1.5 kΩ with a 35 µF bypass. This node carries TWO tubes' cathode current: the tremolo follower V3B lands on it directly, which is why it idles well above a normal 12AX7 cathode and why the tremolo works at all (see the circuit story)",
      "dispute_note": ""
    },
    {
      "node": "P2A",
      "chart": null,
      "sim": 144.665,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — paraphase driver plate (270 kΩ load), the half that drives V5's grid",
      "dispute_note": ""
    },
    {
      "node": "K2A",
      "chart": null,
      "sim": 1.354,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — driver cathode, 2.2 kΩ bypassed by 0.05 µF",
      "dispute_note": ""
    },
    {
      "node": "P2B",
      "chart": null,
      "sim": 181.962,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — paraphase inverted-side plate (270 kΩ load), the half that drives V4's grid",
      "dispute_note": ""
    },
    {
      "node": "K2B",
      "chart": null,
      "sim": 1.861,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — inverted-side cathode, 3.9 kΩ left UNBYPASSED; that degeneration is what trims this half's gain down to the 23.5× the 270 kΩ/12 kΩ divider asks for",
      "dispute_note": ""
    },
    {
      "node": "G2B",
      "chart": null,
      "sim": 0,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — the paraphase tap itself, where the 270 kΩ from V5's grid meets the 12 kΩ to ground. Idles at exactly 0 V: there is no grid-current model (a stated limitation of the corpus's tube models)",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Within target",
      "summary": "2 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.",
        "6 sheet-only parts are explicitly excluded: CB1, CB2, CIN1, CIN2, RMX1, RMX2. 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.",
        "Valco published no board-layout sheet for the 6161 and none was located; this board is derived from the circuit drawing, so no factory drawing can establish its heater legs."
      ],
      "tone": "attention"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Checked",
      "summary": "5 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/6161"
}