* Added filter gain compensation parameter

- No longer hard-wired to 0.5 (50%)

Author: kennethdmiller3

Filter.cpp

@@ -36,14 +36,8 @@ float CubicSaturate(float const x)
 #define Saturate(x) FastTanh(x)
 //#define Saturate(x) tanhf(x)
 
-// compensate for reduced gain at low frequencies as resonance increases
-// 0.0: no compensation, -12dB at low frequencies
-// 0.5: half compensation, -6dB at low frequencies
-// 1.0: full compensation, -0dB at low frequencies
-static float const GAIN_COMPENSATION = 0.5f;
-
 // filter configuration
-FilterConfig flt_config(false, FilterConfig::LOWPASS_4, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
+FilterConfig flt_config(false, FilterConfig::LOWPASS_4, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
 
 // filter envelope config
 EnvelopeConfig flt_env_config(false, 0.0f, 1.0f, 0.0f, 0.1f);
@@ -303,7 +297,7 @@ void FilterState::Setup(float const cutoff, float const resonance, float const s
 float FilterState::Update(FilterConfig const &config, float const input)
 {
 	// input with drive and gain compensation
-	float const input_adjusted = config.drive * (input + input * feedback * GAIN_COMPENSATION);
+	float const input_adjusted = input * config.drive * (1.0f + feedback * config.compensation);
 
 #if FILTER == FILTER_IMPROVED_MOOG
 

Filter.h

@@ -56,6 +56,9 @@ class FilterConfig
 	// drive parameter
 	float drive;
 
+	// gain compensation
+	float compensation;
+
 	// resonance parameter
 	float resonance;
 
@@ -68,9 +71,10 @@ class FilterConfig
 	// key follow
 	float key_follow;
 
-	FilterConfig(bool const enable, Mode const mode, float const drive, float const resonance, float const cutoff_base, float const cutoff_lfo, float const cutoff_env, float const cutoff_env_vel, float const key_follow)
+	FilterConfig(bool const enable, Mode const mode, float const drive, float const compensation, float const resonance, float const cutoff_base, float const cutoff_lfo, float const cutoff_env, float const cutoff_env_vel, float const key_follow)
 		: enable(enable)
 		, drive(drive)
+		, compensation(compensation)
 		, resonance(resonance)
 		, cutoff_base(cutoff_base)
 		, cutoff_lfo(cutoff_lfo)

MenuFLT.cpp

@@ -30,6 +30,9 @@ namespace Menu
 		case DRIVE:
 			UpdatePercentageProperty(flt_config.drive, sign, modifiers, 0, 10);
 			break;
+		case COMPENSATION:
+			UpdatePercentageProperty(flt_config.compensation, sign, modifiers, 0, 1);
+			break;
 		case RESONANCE:
 			UpdatePercentageProperty(flt_config.resonance, sign, modifiers, 0, 4);
 			break;
@@ -81,6 +84,9 @@ namespace Menu
 		case DRIVE:
 			PrintItemFloat(hOut, pos, flags, "Drive:    % 7.1f%%", flt_config.drive * 100.0f);
 			break;
+		case COMPENSATION:
+			PrintItemFloat(hOut, pos, flags, "Gain Comp:% 7.1f%%", flt_config.compensation * 100.0f);
+			break;
 		case RESONANCE:
 			PrintItemFloat(hOut, pos, flags, "Resonance:% 7.1f%%", flt_config.resonance * 100.0f);
 			break;

MenuFLT.h

@@ -18,6 +18,7 @@ namespace Menu
 			TITLE,
 			MODE,
 			DRIVE,
+			COMPENSATION,
 			RESONANCE,
 			CUTOFF_BASE,
 			CUTOFF_LFO,