From 77da69c220dbb7cdccf3b316e567e6ae69a0579d Mon Sep 17 00:00:00 2001
From: Damien Zammit <damien@zamaudio.com>
Date: Mon, 23 Nov 2020 18:21:54 +1100
Subject: ZamTube: Simplify circuit with no Ci capacitor - no sound quality
 loss

---
 plugins/ZamTube/ZamTubePlugin.cpp |  5 +----
 plugins/ZamTube/wdfcircuits.h     | 16 ++++------------
 2 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/plugins/ZamTube/ZamTubePlugin.cpp b/plugins/ZamTube/ZamTubePlugin.cpp
index 4d7c453..7783700 100644
--- a/plugins/ZamTube/ZamTubePlugin.cpp
+++ b/plugins/ZamTube/ZamTubePlugin.cpp
@@ -299,7 +299,6 @@ void ZamTubePlugin::activate()
 	
 	// Passive components
 	/* Original WDF preamp
-	ci[0] = 100e-9;
 	rg[0] = 20e+3;
 	rk[0] = 1e+3;
 	ck[0] = 10e-6;
@@ -310,7 +309,6 @@ void ZamTubePlugin::activate()
 	*/
 	
 	/* Matt's preamp */
-	ci[0] = 100e-9;
 	rg[0] = 1e-3;
 	rk[0] = 1200.; // 820 originally
 	ck[0] = 50e-6;
@@ -320,7 +318,6 @@ void ZamTubePlugin::activate()
 	ro[0] = 470e+3;
 
 	/* CLA's preamp
-	ci[0] = 1.0e-7;
 	rg[0] = 5.6e+3;
 	rk[0] = 1.5e+3;
 	ck[0] = 4.7e-6;
@@ -333,7 +330,7 @@ void ZamTubePlugin::activate()
 	int pre = 0;
 	float volumepot = 800e+3; // 100 good at low gain, 1000 good at high gain 
 	ckt.on = false;
-	ckt.updateRValues(ci[pre], ck[pre], co[pre], e[pre], er[pre], rg[pre], volumepot, rk[pre], 1e+3, ro[pre], Fs);
+	ckt.updateRValues(ck[pre], co[pre], e[pre], er[pre], rg[pre], volumepot, rk[pre], 1e+3, ro[pre], Fs);
 	ckt.warmup_tubes();
 
         fSamplingFreq = Fs;
diff --git a/plugins/ZamTube/wdfcircuits.h b/plugins/ZamTube/wdfcircuits.h
index 816c96d..5bf2e93 100644
--- a/plugins/ZamTube/wdfcircuits.h
+++ b/plugins/ZamTube/wdfcircuits.h
@@ -40,10 +40,9 @@ public:
 		E500E = 0.;
 	}
 
-	void updateRValues(Real C_Ci, Real C_Ck, Real C_Co, Real E_E500, Real R_E500, Real R_Rg, Real R_Ri, Real R_Rk, Real R_Vi, Real R_Ro, Real sampleRate) {
+	void updateRValues(Real C_Ck, Real C_Co, Real E_E500, Real R_E500, Real R_Rg, Real R_Ri, Real R_Rk, Real R_Vi, Real R_Ro, Real sampleRate) {
 
 		Real ViR = R_Vi;
-		Real CiR = 1.0 / (2.0*C_Ci*sampleRate);
 		Real RiR = R_Ri;
 		Real RgR = R_Rg;
 		Real RoR = R_Ro;
@@ -52,10 +51,7 @@ public:
 		Real E500R = R_E500;
 		E500E = E_E500;
 		Real CoR = 1.0 / (2.0*C_Co*sampleRate);
-		Real S0_3R = (CiR + ViR);
-		S0_3Gamma1 = CiR/(CiR + ViR);
-		Assert(S0_3Gamma1 >= 0.0 && S0_3Gamma1 <= 1.0);
-		Real P0_1R = S0_3R;
+		Real P0_1R = ViR;
 		Real P0_2R = RiR;
 		Real P0_3R = 1.0 /(1.0 / P0_1R + 1.0 / P0_2R);
 		P0_3Gamma1 = 1.0 / P0_1R/(1.0 / P0_1R + 1.0 / P0_2R);
@@ -111,11 +107,10 @@ public:
 		//S0_1SetA
 		//ViGetB
 		//S0_2SetA
-		Real S0_3b3 = -(/*Cib*/ + ViE);
 		//P0_1SetA
 		//RiGetB
 		//P0_2SetA
-		Real P0_3b3 = -P0_3Gamma1*(-S0_3b3);
+		Real P0_3b3 = -P0_3Gamma1*ViE;
 		//S1_2SetA
 		Real S1_3b3 = -(P0_3b3);
 		//P1_3GetB
@@ -144,15 +139,12 @@ public:
 		//RkSetA
 		//S1_3SetA
 		//RgSetA
-		Real S1_3b2 = Vg - S1_3Gamma1*(P0_3b3 + Vg);
 		//P0_3SetA
-		Real P0_3b1 = S1_3b2  - S0_3b3 - P0_3Gamma1*(-S0_3b3);
 		//S0_3SetA
-		Real S0_3b1 = /*Cib*/ - S0_3Gamma1*(/*Cib*/ + ViE + P0_3b1);
 		//Cia = S0_3b1;
 		//RiSetA
 		//printf("Vk=%f Vg=%f Vpk=%f  in=%f out=%f\n", Vk,Vg,S2_3b3, ViE,Roa);
-		return -(Roa);
+		return Roa;
 	}
 
 private:
-- 
cgit v1.2.3