class

`SushiDSP::Triode12AX7`

Stateless Koren 12AX7 triode: plate current plus Norman's soft grid-conduction law.

Declared in: include/SushiDSP/circuits/models/Triode12AX7.hpp

Parameters are transcribed from docs/reference/spice/models/12ax7_koren.sub. The two branch voltages are v[0] = Vgk and v[1] = Vpk; the two branch currents are i[0] = Ig and i[1] = Ip. A DK solver wants the currents and the Jacobian at the same operating point, so current_and_jacobian() carries the physics and current()/jacobian() forward to it. Every entry point is allocation-free, throw-free and safe on the audio thread.

Static public attributes

static constexpr std::size_t kBranchCount = 2

Branch 0 is the grid, branch 1 is the plate.

static constexpr double kMu = 100.0

Amplification factor MU (12ax7_koren.sub).

static constexpr double kKp = 600.0

Koren's grid-drive sharpness KP (12ax7_koren.sub).

static constexpr double kKvb = 300.0

Koren's knee-softening constant KVB (12ax7_koren.sub).

static constexpr double kKg1 = 1060.0

Koren's perveance divisor KG1 (12ax7_koren.sub).

static constexpr double kKx = 1.4

Koren's plate-current exponent KX (12ax7_koren.sub).

static constexpr double kGridCurrentScale = 1.0e-6

Norman grid-current scale IG0, in amperes (12ax7_koren.sub).

static constexpr double kGridThresholdVolts = 0.5

Norman grid-conduction threshold VGAMMA, in volts (12ax7_koren.sub).

static constexpr double kGridTransitionVolts = 0.15

Norman grid-conduction transition width VTG, in volts (12ax7_koren.sub).

Public member functions

void current_and_jacobian(const std::array< double, 2 > &v, std::array< double, 2 > &i, std::array< std::array< double, 2 >, 2 > &j) const

Evaluates both branch currents and the 2x2 Jacobian at one operating point.

The plate law's root, softplus, logistic and E1^(kx-1) are shared between the current and its derivative, and E1^kx is formed as E1^(kx-1) * E1 rather than by a second pow. current() and jacobian() forward here.

Parameters

v: Branch voltages: v[0] = Vgk, v[1] = Vpk, in volts.
i: Receives the branch currents: i[0] = Ig, i[1] = Ip, in amperes.
j: Receives the 2x2 Jacobian j[a][b] = d i_a / d v_b in siemens.

void current(const std::array< double, 2 > &v, std::array< double, 2 > &i) const

Evaluates the grid and plate currents at one operating point.

Parameters

v: Branch voltages: v[0] = Vgk, v[1] = Vpk, in volts.
i: Receives the branch currents: i[0] = Ig, i[1] = Ip, in amperes.

void jacobian(const std::array< double, 2 > &v, std::array< std::array< double, 2 >, 2 > &j) const

Evaluates the branch-current Jacobian j[a][b] = d i_a / d v_b at one point.

Parameters

v: Branch voltages: v[0] = Vgk, v[1] = Vpk, in volts.
j: Receives the 2x2 Jacobian in siemens; j[0][1] is exactly zero because the grid current depends on Vgk alone.