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Fix bugs with ladder filter feedback and highpass modes #203

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merged 2 commits into from
Sep 20, 2024
Merged

Fix bugs with ladder filter feedback and highpass modes #203

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0dd093c
Fix bug with ladder filter feedback and first stage
ndonald2 Feb 23, 2024
20107ec
Use scaled drive factor in ladder
ndonald2 Apr 19, 2024
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11 changes: 5 additions & 6 deletions Source/Filters/ladder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@
// Huovilainen New Moog (HNM) model as per CMJ jun 2006
// Richard van Hoesel, v. 1.03, Feb. 14 2021
// v1.7 (Infrasonic/Daisy) add configurable filter mode
// v1.6 (Infrasonic/Daisy) removes polyphase FIR, uses 2x linear
// v1.6 (Infrasonic/Daisy) removes polyphase FIR, uses 4x linear
// oversampling for performance reasons
// v1.5 adds polyphase FIR or Linear interpolation
// v1.4 FC extended to 18.7kHz, max res to 1.8, 4x oversampling,
Expand Down Expand Up @@ -70,20 +70,19 @@ void LadderFilter::Init(float sample_rate)

float LadderFilter::Process(float in)
{
float input = in * drive_;
float input = in * drive_scaled_;
float total = 0.0f;
float interp = 0.0f;
for(size_t os = 0; os < kInterpolation; os++)
{
float u = (interp * oldinput_ + (1.0f - interp) * input)
- (z1_[3] - pbg_ * input) * K_ * Qadjust_;
float in_interp = (interp * oldinput_ + (1.0f - interp) * input);
float u = in_interp - (z1_[3] - pbg_ * in_interp) * K_ * Qadjust_;
u = fast_tanh(u);
float stage1 = LPF(u, 0);
float stage2 = LPF(stage1, 1);
float stage3 = LPF(stage2, 2);
float stage4 = LPF(stage3, 3);
total += weightedSumForCurrentMode(
{input, stage1, stage2, stage3, stage4})
total += weightedSumForCurrentMode({u, stage1, stage2, stage3, stage4})
* kInterpolationRecip;
interp += kInterpolationRecip;
}
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