sst::filters::TriPoleFilter Namespace Reference

This filter is an emulation of the "Threeler" VCF by Ian Fritz (https://ijfritz.byethost4.com/Threeler_board_doc.pdf). More...

Namespaces
	OnePoleHPF
	OnePoleHPF_FB
	OnePoleLPF
	OnePoleLPF_FB
	ResWaveshaper

Enumerations
enum	thr_coeffs {   thr_b0 = 0 , thr_a0 , thr_b1 , thr_a1 ,   thr_b2 , thr_a2 , thr_k , n_thr_coeff }
enum	thr_state {   thr_z0 , thr_x0 , thr_z1 , thr_x1 ,   thr_z2 , thr_x2 , thr_fb , thr_fb1 }

Functions
template<typename TuningProvider >
void	makeCoefficients (FilterCoefficientMaker< TuningProvider > *cm, float freq, float reso, int, float sampleRate, TuningProvider *provider)
template<FilterSubType subtype>
SIMD_M128	process (QuadFilterUnitState *__restrict f, SIMD_M128 in)

Variables
constexpr float	res_gain = 1.5f
constexpr float	in_gain = 4.0f
constexpr float	out_gain = 1.0f / in_gain
constexpr int	nIterGlobal = 3
constexpr int	nIterStage = 1
constexpr float	ota1bp = 0.88f
constexpr float	ota1bn = 1.0f
constexpr float	ota2bp = 0.9f
constexpr float	ota2bn = 0.97f
constexpr float	ota3bp = 0.95f
constexpr float	ota3bn = 1.025f
constexpr float	Iabc = 8.0f
constexpr float	Rload = 220.0f
const auto	res_factor_db = std::log10(Iabc * Rload)

Detailed Description

This filter is an emulation of the "Threeler" VCF by Ian Fritz (https://ijfritz.byethost4.com/Threeler_board_doc.pdf).

The filter consists of three one-pole filters with nonlinear resonance and global feedback. The filter has four "modes":

1. LPF -> LPF -> LPF
2. LPF -> HPF -> LPF
3. HPF -> LPF -> HPF
4. HPF -> HPF -> HPF The filter has three output points. For modes and three output points makes for a total of 12 sub-types.

The details of the emulation are derived in a Python notebook here: https://github.com/surge-synthesizer/surge-python/blob/main/scripts/dsp_simulations/ThreelerAnalysis.ipynb

Enumeration Type Documentation

thr_coeffs

enum thr_coeffs

Enumerator
thr_b0
thr_a0
thr_b1
thr_a1
thr_b2
thr_a2
thr_k
n_thr_coeff

thr_state

enum thr_state

Enumerator
thr_z0
thr_x0
thr_z1
thr_x1
thr_z2
thr_x2
thr_fb
thr_fb1

Function Documentation

makeCoefficients()

void sst::filters::TriPoleFilter::makeCoefficients	(	FilterCoefficientMaker< TuningProvider > *	cm,
		float	freq,
		float	reso,
		int	,
		float	sampleRate,
		TuningProvider *	provider
	)

References FilterCoefficientMaker< TuningProvider >::FromDirect(), sst::filters::n_cm_coeffs, res_factor_db, thr_a0, thr_a1, thr_a2, thr_b0, thr_b1, thr_b2, and thr_k.

Referenced by FilterCoefficientMaker< TuningProvider >::MakeCoeffs().

process()

SIMD_M128 sst::filters::TriPoleFilter::process	(	QuadFilterUnitState *__restrict	f,
		SIMD_M128	in
	)

References A, D, F, in_gain, M, n_thr_coeff, nIterGlobal, ota1bp, ota2bn, ota2bp, ota3bn, ota3bp, out_gain, res_gain, S, thr_a0, thr_a1, thr_a2, thr_b0, thr_b1, thr_b2, thr_fb, thr_fb1, thr_k, thr_x0, thr_x1, thr_x2, thr_z0, thr_z1, and thr_z2.

Variable Documentation

res_gain

constexpr float res_gain = 1.5f

constexpr

Referenced by process().

in_gain

constexpr float in_gain = 4.0f

constexpr

Referenced by process().

out_gain

constexpr float out_gain = 1.0f / in_gain

constexpr

Referenced by process().

nIterGlobal

constexpr int nIterGlobal = 3

constexpr

Referenced by process().

nIterStage

constexpr int nIterStage = 1

constexpr

ota1bp

constexpr float ota1bp = 0.88f

constexpr

Referenced by process().

ota1bn

constexpr float ota1bn = 1.0f

constexpr

ota2bp

constexpr float ota2bp = 0.9f

constexpr

Referenced by process().

ota2bn

constexpr float ota2bn = 0.97f

constexpr

Referenced by process().

ota3bp

constexpr float ota3bp = 0.95f

constexpr

Referenced by process().

ota3bn

constexpr float ota3bn = 1.025f

constexpr

Referenced by process().

Iabc

constexpr float Iabc = 8.0f

constexpr

Rload

constexpr float Rload = 220.0f

constexpr

res_factor_db

const auto res_factor_db = std::log10(Iabc * Rload)

Referenced by makeCoefficients().