tubes.lib

Vacuum tube amplifier stage emulations from the Guitarix project. The transfer curve of each tube is stored as a precomputed table (tubetable_*), interpolated at run time; tubestage wraps one table into a complete gain stage with its cathode-capacitor highpass. The T1_*/T2_*/T3_* functions below instantiate the first, second and third preamp stage of each supported tube model.

The models are normally used through their own namespace:

tu = library("tubes.lib");
process = tu.T1_12AX7 : *(preamp) : tu.T2_12AX7;

References

rtable

Read one entry of a waveform table (rdtable with the index truncated to an int).

Usage

rtable(table, r) : _

Where:

  • table: a waveform primitive
  • r: the index to read (truncated to an int)

Test

tu = library("tubes.lib");
tu_rtable_test = tu.rtable(waveform{0.0, 1.0, 2.0, 3.0}, 2);

inverse

Change the sign of the input signal x.

Usage

_ : inverse : _

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tu_inverse_test = os.osc(440) : tu.inverse;

ccopysign

Compose the magnitude of f with the sign of x, following the sign convention below.

Usage

ccopysign(f, x) : _

Where:

  • f: the signal giving the magnitude
  • x: the signal giving the sign

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tu_ccopysign_test = tu.ccopysign(0.5, os.osc(440));

sign, invsign

Sign (-1 for x<0, 1 otherwise) and reversed sign (1 for x<0, -1 otherwise) of a signal x.

Usage

_ : sign : _
_ : invsign : _

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tu_sign_test = os.osc(440) : tu.sign;
tu_invsign_test = os.osc(440) : tu.invsign;

interpolation

Interpolate linearly between the entries i and i+1 of a table with coefficient f.

Usage

interpolation(table, f, i) : _

Where:

  • table: a waveform primitive
  • f: interpolation coefficient between 0 and 1
  • i: the lower table index

Test

tu = library("tubes.lib");
tu_interpolation_test = tu.interpolation(waveform{0.0, 1.0, 2.0, 3.0}, 0.5, 1);

boundIndex

Bound an index to the table boundaries [0, size-1].

Usage

boundIndex(size, index) : _

Test

tu = library("tubes.lib");
tu_boundIndex_test = tu.boundIndex(2000, 2500);

boundFactor

Interpolation factor bounded at the table edges: the fractional part factor - index in range, clipped to 0 below the table (hold the first entry) and to 1 above it (reach the last entry, which sits one past size-1 — the tables are allocated one point larger for exactly this purpose).

Usage

boundFactor(size, factor, index) : _

Where:

  • size: the table size (kept for signature compatibility)
  • factor: the unbounded fractional index
  • index: the bounded integer index (from boundIndex)

Test

tu = library("tubes.lib");
tu_boundFactor_test = tu.boundFactor(2000, 1500.5, 1500);

tubeF

Look up x in a transfer-curve table with linear interpolation: maps the input range starting at low onto the table entries, step entries per input unit, bounded to the table edges.

Usage

_ : tubeF(table, low, high, step, size) : _

Where:

  • table: a waveform primitive holding the transfer curve
  • low: input value mapped to the first entry
  • high: input value mapped to the last entry (informative)
  • step: number of table entries per input unit
  • size: the table size used for bounding

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tu_tubeF_test = os.osc(440) : tu.tubeF(tu.tubetable_12AX7_0, -5, 5, 200, 2000);

getFactor

The interpolation factor tubeF feeds to interpolation: the fractional part of the table index of x, bounded at the table edges.

Usage

getFactor(low, step, size, x) : _

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tu_getFactor_test = tu.getFactor(-5, 200, 2000, os.osc(440));

tubestage, tubestage130_20, tubestageF

tubestage — response plots

One complete triode gain stage: table-driven waveshaping followed by the highpass formed by the cathode capacitor and resistor. tubestageF(tb,vplus,divider,fck,Rk,Vk0) is the fully parameterized form; tubestage(tb,fck,Rk,Vk0) uses the standard 250V supply with divider 40, and tubestage130_20(tb,fck,Rk,Vk0) a 130V supply with divider 20.

Usage

_ : tubestage(tb,fck,Rk,Vk0) : _
_ : tubestage130_20(tb,fck,Rk,Vk0) : _
_ : tubestageF(tb,vplus,divider,fck,Rk,Vk0) : _

Where:

  • tb: a tube transfer-curve table (one of the tubetable_* waveforms)
  • vplus: supply voltage in Volts (tubestageF only)
  • divider: output voltage divider factor (tubestageF only)
  • fck: cutoff frequency in Hz of the cathode highpass
  • Rk: cathode resistor value in Ohms
  • Vk0: quiescent cathode voltage in Volts

Test

tu = library("tubes.lib");
os = library("oscillators.lib");
tubestage_test = os.osc(440) : tu.tubestage(tu.tubetable_12AX7_0, 86.0, 2700.0, 1.581656);
tubestage130_20_test = os.osc(440) : tu.tubestage130_20(tu.tubetable_6DJ8_0, 86.0, 2700.0, 1.863946);
tubestageF_test = os.osc(440) : tu.tubestageF(tu.tubetable_12AX7_0, 250.0, 40.0, 86.0, 2700.0, 1.581656);

T1_12AX7, T2_12AX7, T3_12AX7

T1_12AX7 — response plots

First, second and third preamp stage of a 12AX7 (high-gain dual triode, the classic guitar preamp tube), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_12AX7 : _

T1_12AT7, T2_12AT7, T3_12AT7

T1_12AT7 — response plots

First, second and third preamp stage of a 12AT7 (medium-gain dual triode), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_12AT7 : _

T1_12AU7, T2_12AU7, T3_12AU7

T1_12AU7 — response plots

First, second and third preamp stage of a 12AU7 (low-gain dual triode), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_12AU7 : _

T1_6V6, T2_6V6, T3_6V6

T1_6V6 — response plots

First, second and third preamp stage of a 6V6 (beam power tetrode, wired as a triode), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_6V6 : _

T1_6DJ8, T2_6DJ8, T3_6DJ8

T1_6DJ8 — response plots

First, second and third preamp stage of a 6DJ8 / ECC88 (low-noise dual triode), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_6DJ8 : _

T1_6C16, T2_6C16, T3_6C16

T1_6C16 — response plots

First, second and third preamp stage of a 6C16 (single triode), with the bias values used by the Guitarix amplifiers.

Usage

_ : T1_6C16 : _

tubetable_6C16_0, tubetable_6C16_1, tubetable_6C16_rtable_0, tubetable_6C16_rtable_1

Precomputed transfer-curve tables of the 6C16 triode, sampled at the two operating points used by the T1_6C16..T3_6C16 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage(tubetable_6C16_0,fck,Rk,Vk0) : _
tubetable_6C16_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_6C16_test = tu.tubetable_6C16_rtable_0(100), tu.tubetable_6C16_rtable_1(100);

tubetable_6DJ8_0, tubetable_6DJ8_1, tubetable_6DJ8_rtable_0, tubetable_6DJ8_rtable_1

Precomputed transfer-curve tables of the 6DJ8 triode, sampled at the two operating points used by the T1_6DJ8..T3_6DJ8 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage130_20(tubetable_6DJ8_0,fck,Rk,Vk0) : _
tubetable_6DJ8_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_6DJ8_test = tu.tubetable_6DJ8_rtable_0(100), tu.tubetable_6DJ8_rtable_1(100);

tubetable_6V6_0, tubetable_6V6_1, tubetable_6V6_rtable_0, tubetable_6V6_rtable_1

Precomputed transfer-curve tables of the 6V6 tube, sampled at the two operating points used by the T1_6V6..T3_6V6 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage(tubetable_6V6_0,fck,Rk,Vk0) : _
tubetable_6V6_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_6V6_test = tu.tubetable_6V6_rtable_0(100), tu.tubetable_6V6_rtable_1(100);

tubetable_12AT7_0, tubetable_12AT7_1, tubetable_12AT7_rtable_0, tubetable_12AT7_rtable_1

Precomputed transfer-curve tables of the 12AT7 triode, sampled at the two operating points used by the T1_12AT7..T3_12AT7 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage(tubetable_12AT7_0,fck,Rk,Vk0) : _
tubetable_12AT7_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_12AT7_test = tu.tubetable_12AT7_rtable_0(100), tu.tubetable_12AT7_rtable_1(100);

tubetable_12AU7_0, tubetable_12AU7_1, tubetable_12AU7_rtable_0, tubetable_12AU7_rtable_1

Precomputed transfer-curve tables of the 12AU7 tube, sampled at the two operating points used by the T1_12AU7..T3_12AU7 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage(tubetable_12AU7_0,fck,Rk,Vk0) : _
tubetable_12AU7_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_12AU7_test = tu.tubetable_12AU7_rtable_0(100), tu.tubetable_12AU7_rtable_1(100);

tubetable_12AX7_0, tubetable_12AX7_1, tubetable_12AX7_rtable_0, tubetable_12AX7_rtable_1

Precomputed transfer-curve tables of the 12AX7 triode, sampled at the two operating points used by the T1_12AX7..T3_12AX7 stages (_0 and _1). The _rtable_* forms read one raw entry.

Usage

_ : tubestage(tubetable_12AX7_0,fck,Rk,Vk0) : _
tubetable_12AX7_rtable_0(r) : _

Test

tu = library("tubes.lib");
tubetable_12AX7_test = tu.tubetable_12AX7_rtable_0(100), tu.tubetable_12AX7_rtable_1(100);