From 75f3211629ec54526b2ddbb634a023d97a3ebd88 Mon Sep 17 00:00:00 2001
From: Oleksiy <sleepy@sleepy.kiev.ua>
Date: Sun, 20 Sep 2026 01:13:50 +0300
Subject: [PATCH] Switched back to SVF bacause of the instability of Resonant
 Filter

---
 Acid/Acid.ino | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/Acid/Acid.ino b/Acid/Acid.ino
index 78ed33b..58728a6 100644
--- a/Acid/Acid.ino
+++ b/Acid/Acid.ino
@@ -7,7 +7,6 @@
 // This code is licenced under GPL v3 or later
 
 // todo:
-// debug accent handling that overloads the filter, also accent can be too short or too long if it's relying on midi note
 // add overdrive
 // frequency from CV (noteFreq) could be Q16n16 for consistency
 
@@ -15,7 +14,8 @@
 #include <MIDI.h>
 #include <Oscil.h>
 #include <MetaOscil.h>
-#include <ResonantFilter.h>
+//#include <ResonantFilter.h>
+#include <StateVariable.h>
 #include <Ead.h>
 #include <Portamento.h>
 #include <mozzi_midi.h>
@@ -99,16 +99,20 @@ Oscil <SAW_MAX_8192_AT_16384_512_NUM_CELLS, MOZZI_AUDIO_RATE> aSaw8192(SAW_MAX_8
 MetaOscil<SAW_MAX_138_AT_16384_512_NUM_CELLS, MOZZI_AUDIO_RATE, 16> aSaw {&aSaw138, &aSaw154, &aSaw182, &aSaw240, &aSaw292, &aSaw341, &aSaw390, &aSaw431, &aSaw512, &aSaw630, &aSaw744, &aSaw1170, &aSaw1638, &aSaw2730, &aSaw4096, &aSaw8192};
 
 IntMap kMapNote(         0, 4095, 24 * pitchSubSteps, 84 * pitchSubSteps );
-IntMap kMapCutoff(       0, 1023, 26,  100   );
+//IntMap kMapCutoff(       0, 1023, 26,  100   ); //for lpf
+//IntMap kMapResonance(    0, 1023, 0,   255   );
+IntMap kMapCutoff(       0, 1023, 400, 3600  );
+IntMap kMapResonance(    0, 1023, 200, 64    );
 IntMap kMapEnvMod(       0, 1023, 0,   140   );
-IntMap kMapResonance(    0, 1023, 0,   255   );
 IntMap kMapDrive(        0, 1023, 0,   400   );
 IntMap kMapAttack(       0, 1023, 1,   100   );
 IntMap kMapDecay(        0, 1023, 100, 1500  );
 IntMap kMapAccentLevel(  0, 1023, 0,   128   );
 
 Ead kEnvelope(MOZZI_CONTROL_RATE);
-LowPassFilter lpfr;
+//LowPassFilter lpf;
+StateVariable <LOWPASS> svf;
+
 Portamento <MOZZI_CONTROL_RATE> kGlide;
 
 //Global variables
@@ -271,8 +275,11 @@ void updateControl(){
   //Remap the values and assign to parameters
   int accentLevel = kMapAccentLevel(knobSVal);
   int baseCutoff = kMapCutoff(knob1Val);
-  int cutoff = accent? (baseCutoff + (((long)accentLevel * (100 - baseCutoff)) >> 7)) : baseCutoff;
-  int resonance = accent? (255 - (((long)(128 - accentLevel) * (255 - kMapResonance(knob2Val))) >> 7)) : kMapResonance(knob2Val);
+  //int cutoff = accent? (baseCutoff + (((long)accentLevel * (100 - baseCutoff)) >> 7)) : baseCutoff; //lpf version
+  int cutoff = accent? (baseCutoff + (((long)accentLevel * (3600 - baseCutoff)) >> 7)) : baseCutoff; //svf version
+  //int resonance = accent? (255 - (((long)(128 - accentLevel) * (255 - kMapResonance(knob2Val))) >> 7)) : kMapResonance(knob2Val); //lpf version
+  int baseResonance = kMapResonance(knob2Val);
+  int resonance = accent? (baseResonance - (((long)accentLevel * (baseResonance - 64)) >> 7)) : baseResonance;
   int envMod = kMapEnvMod(knob3Val);
   driveAmount = kMapDrive(knob4Val);
   
@@ -319,7 +326,9 @@ void updateControl(){
 
   gain = accent? constrain(env + (((long)env * accentLevel) >> 7), 0, 255) : env; //needs finetuning
 
-  lpfr.setCutoffFreqAndResonance(constrain(cutoff + (((long)env * envMod * cutoff)>>16), 0, 255), resonance);
+  //lpf.setCutoffFreqAndResonance(constrain(cutoff + (((long)env * envMod * cutoff)>>16), 0, 255), resonance);
+  svf.setCentreFreq(cutoff + (((long)env * envMod * cutoff)>>16));
+  svf.setResonance(resonance);
 }
 
 AudioOutput updateAudio(){
@@ -329,7 +338,8 @@ AudioOutput updateAudio(){
   } else {
     signal = aSaw.next();
   }
-  signal = lpfr.next(signal); //filter
+  //signal = lpf.next(signal); //filter
+  signal = svf.next(signal);
   signal = (signal * gain); //envelope
   //signal = softClip((signal * (127 + driveAmount)) >> 9); //overdrive
   //signal = (signal * makeupGain) >> 7; //makeup gain compensation