diff --git a/include/BasicFilters.h b/include/BasicFilters.h
index 98c69474a..e09d40c42 100644
--- a/include/BasicFilters.h
+++ b/include/BasicFilters.h
@@ -75,34 +75,34 @@ public:
 	inline void setCoeffs( float freq )
 	{
 		// wc
-		const float wc = F_2PI * freq;
+		const float wc = F_2PI * freq / m_sampleRate;
 		const float wc2 = wc * wc;
 		const float wc3 = wc2 * wc;
 		m_wc4 = wc2 * wc2;
 
 		// k
-		const float k = wc / tanf( F_PI * freq / m_sampleRate );
+		const float k = wc / tan( wc * 0.5 );
 		const float k2 = k * k;
 		const float k3 = k2 * k;
 		m_k4 = k2 * k2;
 
 		// a
-		static const float sqrt2 = sqrtf( 2.0f );
+		static const double sqrt2 = sqrt( 2.0 );
 		const float sq_tmp1 = sqrt2 * wc3 * k;
 		const float sq_tmp2 = sqrt2 * wc * k3;
-		m_a = 4.0f * wc2 * k2 + 2.0f * sq_tmp1 + m_k4 + 2.0f * sq_tmp2 + m_wc4;
+		m_a = 1.0f / ( 4.0f * wc2 * k2 + 2.0f * sq_tmp1 + m_k4 + 2.0f * sq_tmp2 + m_wc4 );
 
 		// b
-		m_b1 = ( 4.0f * ( m_wc4 + sq_tmp1 - m_k4 - sq_tmp2 ) ) / m_a;
-		m_b2 = ( 6.0f * m_wc4 - 8.0f * wc2 * k2 + 6.0f * m_k4 ) / m_a;
-		m_b3 = ( 4.0f * ( m_wc4 - sq_tmp1 + sq_tmp2 - m_k4 ) ) / m_a;
-		m_b4 = ( m_k4 - 2.0f * sq_tmp1 + m_wc4 - 2.0f * sq_tmp2 + 4.0f * wc2 * k2 ) / m_a;
+		m_b1 = ( 4.0f * ( m_wc4 + sq_tmp1 - m_k4 - sq_tmp2 ) ) * m_a;
+		m_b2 = ( 6.0f * m_wc4 - 8.0f * wc2 * k2 + 6.0f * m_k4 ) * m_a;
+		m_b3 = ( 4.0f * ( m_wc4 - sq_tmp1 + sq_tmp2 - m_k4 ) ) * m_a;
+		m_b4 = ( m_k4 - 2.0f * sq_tmp1 + m_wc4 - 2.0f * sq_tmp2 + 4.0f * wc2 * k2 ) * m_a;
 	}
 
 	inline void setLowpass( float freq )
 	{
 		setCoeffs( freq );
-		m_a0 = m_wc4 / m_a;
+		m_a0 = m_wc4 * m_a;
 		m_a1 = 4.0f * m_a0;
 		m_a2 = 6.0f * m_a0;
 	}
@@ -110,7 +110,7 @@ public:
 	inline void setHighpass( float freq )
 	{
 		setCoeffs( freq );
-		m_a0 = m_k4 / m_a;
+		m_a0 = m_k4 * m_a;
 		m_a1 = 4.0f * m_a0;
 		m_a2 = 6.0f * m_a0;
 	}
diff --git a/include/lmms_constants.h b/include/lmms_constants.h
index 629db886c..6f50c6f8e 100644
--- a/include/lmms_constants.h
+++ b/include/lmms_constants.h
@@ -25,15 +25,28 @@
 #ifndef LMMS_CONSTANTS_H
 #define LMMS_CONSTANTS_H
 
-const double D_PI = 3.14159265358979323846;
-const double D_2PI = D_PI * 2.0;
-const double D_PI_2 = D_PI * 0.5;
-const double D_E = 2.71828182845904523536; 
+const long double LD_PI = 3.14159265358979323846264338327950288419716939937510;
+const long double LD_2PI = LD_PI * 2.0;
+const long double LD_PI_2 = LD_PI * 0.5;
+const long double LD_PI_R = 1.0 / LD_PI;
+const long double LD_PI_SQR = LD_PI * LD_PI;
+const long double LD_E = 2.71828182845904523536028747135266249775724709369995;
+const long double LD_E_R = 1.0 / LD_E;
 
-const float F_PI = (float) D_PI;
-const float F_2PI = (float) D_2PI;
-const float F_PI_2 = (float) D_PI_2;
-const float F_E = (float) D_E;
+const double D_PI = (double) LD_PI;
+const double D_2PI = (double) LD_2PI;
+const double D_PI_2 = (double) LD_PI_2;
+const double D_PI_R = (double) LD_PI_R;
+const double D_PI_SQR = (double) LD_PI_SQR;
+const double D_E = (double) LD_E;
+const double D_E_R = (double) LD_E_R;
 
+const float F_PI = (float) LD_PI;
+const float F_2PI = (float) LD_2PI;
+const float F_PI_2 = (float) LD_PI_2;
+const float F_PI_R = (float) LD_PI_R;
+const float F_PI_SQR = (float) LD_PI_SQR;
+const float F_E = (float) LD_E;
+const float F_E_R = (float) LD_E_R;
 
 #endif
diff --git a/include/lmms_math.h b/include/lmms_math.h
index 016e1a49f..7cde29153 100644
--- a/include/lmms_math.h
+++ b/include/lmms_math.h
@@ -289,4 +289,18 @@ static inline float fastSqrt( float n )
 	return u.f;
 }
 
+//! returns value furthest from zero
+template<class T>
+static inline T absMax( T a, T b )
+{
+	return qAbs<T>(a) > qAbs<T>(b) ? a : b;
+}
+
+//! returns value nearest to zero
+template<class T>
+static inline T absMin( T a, T b )
+{
+	return qAbs<T>(a) < qAbs<T>(b) ? a : b;
+}
+
 #endif
diff --git a/plugins/Bitcrush/Bitcrush.cpp b/plugins/Bitcrush/Bitcrush.cpp
index e9ab9639a..84f5b45ba 100644
--- a/plugins/Bitcrush/Bitcrush.cpp
+++ b/plugins/Bitcrush/Bitcrush.cpp
@@ -30,6 +30,8 @@ const int OS_RATE = 5;
 const float OS_RATIO = 1.0f / OS_RATE;
 const float CUTOFF_RATIO = 0.353553391f;
 const int SILENCEFRAMES = 10;
+const float OS_RESAMPLE [5] = { 0.0001490062883964112, 0.1645978376763992, 0.6705063120704088,
+		0.1645978376763992, 0.0001490062883964112 };
 
 extern "C"
 {
@@ -78,7 +80,7 @@ void BitcrushEffect::sampleRateChanged()
 {
 	m_sampleRate = Engine::mixer()->processingSampleRate();
 	m_filter.setSampleRate( m_sampleRate );
-	m_filter.setLowpass( m_sampleRate * CUTOFF_RATIO );
+	m_filter.setLowpass( m_sampleRate * ( CUTOFF_RATIO * OS_RATIO ) );
 	m_needsUpdate = true;
 }
 
@@ -95,6 +97,11 @@ inline float BitcrushEffect::noise( float amt )
 
 bool BitcrushEffect::processAudioBuffer( sampleFrame* buf, const fpp_t frames )
 {
+	if( !isEnabled() || !isRunning () )
+	{
+		return( false );
+	}
+
 	// update values
 	if( m_needsUpdate || m_controls.m_rateEnabled.isValueChanged() )
 	{
@@ -219,8 +226,8 @@ bool BitcrushEffect::processAudioBuffer( sampleFrame* buf, const fpp_t frames )
 		float rsum = 0.0f;
 		for( int o = 0; o < OS_RATE; ++o )
 		{
-			lsum += m_buffer[f * OS_RATE + o][0] * OS_RATIO;
-			rsum += m_buffer[f * OS_RATE + o][1] * OS_RATIO;
+			lsum += m_buffer[f * OS_RATE + o][0] * OS_RESAMPLE[o];
+			rsum += m_buffer[f * OS_RATE + o][1] * OS_RESAMPLE[o];
 		}
 		buf[f][0] = d * buf[f][0] + w * qBound( -m_outClip, lsum, m_outClip ) * m_outGain;
 		buf[f][1] = d * buf[f][1] + w * qBound( -m_outClip, rsum, m_outClip ) * m_outGain;
diff --git a/src/core/FxMixer.cpp b/src/core/FxMixer.cpp
index 797463d0d..358e31171 100644
--- a/src/core/FxMixer.cpp
+++ b/src/core/FxMixer.cpp
@@ -100,7 +100,7 @@ inline void FxChannel::processed()
 void FxChannel::incrementDeps()
 {
 	m_dependenciesMet.ref();
-	if( m_dependenciesMet >= m_receives.size() )
+	if( m_dependenciesMet >= m_receives.size() && ! m_queued )
 	{
 		m_queued = true;
 		MixerWorkerThread::addJob( this );