diff --git a/plugins/channelrx/demoddsd/dsddecoder.h b/plugins/channelrx/demoddsd/dsddecoder.h
index 566a6e623..525281a8d 100644
--- a/plugins/channelrx/demoddsd/dsddecoder.h
+++ b/plugins/channelrx/demoddsd/dsddecoder.h
@@ -70,6 +70,7 @@ public:
     void setAudioGain(float gain) { m_decoder.setAudioGain(gain); }
     void setBaudRate(int baudRate);
     void setSymbolPLLLock(bool pllLock) { m_decoder.setSymbolPLLLock(pllLock); }
+    void useHPMbelib(bool useHP) { m_decoder.useHPMbelib(useHP); }
 
 private:
     DSDcc::DSDDecoder m_decoder;
diff --git a/plugins/channelrx/demoddsd/dsddemod.cpp b/plugins/channelrx/demoddsd/dsddemod.cpp
index 9f03195a4..3e9ee2a59 100644
--- a/plugins/channelrx/demoddsd/dsddemod.cpp
+++ b/plugins/channelrx/demoddsd/dsddemod.cpp
@@ -215,6 +215,7 @@ void DSDDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
                                 m_dsdDecoder.getMbeRateIndex(),
                                 m_settings.m_volume * 10.0,
                                 m_settings.m_tdmaStereo ? 1 : 3, // left or both channels
+                                m_settings.m_highPassFilter,
                                 &m_audioFifo1);
                     }
 
@@ -230,6 +231,7 @@ void DSDDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
                                 m_dsdDecoder.getMbeRateIndex(),
                                 m_settings.m_volume * 10.0,
                                 m_settings.m_tdmaStereo ? 2 : 3, // right or both channels
+                                m_settings.m_highPassFilter,
                                 &m_audioFifo2);
                     }
 
@@ -375,6 +377,7 @@ bool DSDDemod::handleMessage(const Message& cmd)
                 << " m_udpCopyAudio: " << m_settings.m_udpCopyAudio
                 << " m_udpAddress: " << m_settings.m_udpAddress
                 << " m_udpPort: " << m_settings.m_udpPort
+                << " m_highPassFilter: "<< m_settings.m_highPassFilter
                 << " force: " << cfg.getForce();
 
         return true;
@@ -467,6 +470,11 @@ void DSDDemod::applySettings(DSDDemodSettings& settings, bool force)
         m_audioFifo2.setCopyToUDP(settings.m_slot2On && !settings.m_slot1On && settings.m_udpCopyAudio);
     }
 
+    if ((settings.m_highPassFilter != m_settings.m_highPassFilter) || force)
+    {
+        m_dsdDecoder.useHPMbelib(settings.m_highPassFilter);
+    }
+
     m_settings = settings;
 }
 
diff --git a/plugins/channelrx/demoddsd/dsddemodgui.cpp b/plugins/channelrx/demoddsd/dsddemodgui.cpp
index 00e8a5663..e74e2e6d1 100644
--- a/plugins/channelrx/demoddsd/dsddemodgui.cpp
+++ b/plugins/channelrx/demoddsd/dsddemodgui.cpp
@@ -196,6 +196,12 @@ void DSDDemodGUI::on_audioMute_toggled(bool checked)
     applySettings();
 }
 
+void DSDDemodGUI::on_highPassFilter_toggled(bool checked)
+{
+    m_settings.m_highPassFilter = checked;
+    applySettings();
+}
+
 void DSDDemodGUI::on_symbolPLLLock_toggled(bool checked)
 {
     if (checked) {
diff --git a/plugins/channelrx/demoddsd/dsddemodgui.h b/plugins/channelrx/demoddsd/dsddemodgui.h
index cede0f549..40fa8e18d 100644
--- a/plugins/channelrx/demoddsd/dsddemodgui.h
+++ b/plugins/channelrx/demoddsd/dsddemodgui.h
@@ -124,6 +124,7 @@ private slots:
     void on_fmDeviation_valueChanged(int value);
     void on_squelchGate_valueChanged(int value);
     void on_squelch_valueChanged(int value);
+    void on_highPassFilter_toggled(bool checked);
     void on_audioMute_toggled(bool checked);
     void on_symbolPLLLock_toggled(bool checked);
     void on_udpOutput_toggled(bool checked);
diff --git a/plugins/channelrx/demoddsd/dsddemodgui.ui b/plugins/channelrx/demoddsd/dsddemodgui.ui
index 1e8777b28..6ac50170c 100644
--- a/plugins/channelrx/demoddsd/dsddemodgui.ui
+++ b/plugins/channelrx/demoddsd/dsddemodgui.ui
@@ -584,7 +584,7 @@
        <widget class="QLabel" name="volumeText">
         <property name="minimumSize">
          <size>
-          <width>0</width>
+          <width>30</width>
           <height>0</height>
          </size>
         </property>
@@ -598,7 +598,7 @@
          <string>Sound volume</string>
         </property>
         <property name="text">
-         <string>2.0</string>
+         <string>10.0</string>
         </property>
         <property name="alignment">
          <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
@@ -828,7 +828,7 @@
       <item>
        <widget class="ButtonSwitch" name="highPassFilter">
         <property name="toolTip">
-         <string>Toggle audio high pass filter for mbelib (&gt;300 Hz)</string>
+         <string>Toggle audio high pass filter</string>
         </property>
         <property name="text">
          <string/>
diff --git a/plugins/samplesource/filesource/filesourcegui.cpp b/plugins/samplesource/filesource/filesourcegui.cpp
index af431da91..4d0c392c1 100644
--- a/plugins/samplesource/filesource/filesourcegui.cpp
+++ b/plugins/samplesource/filesource/filesourcegui.cpp
@@ -134,8 +134,6 @@ void FileSourceGui::handleInputMessages()
 
     while ((message = m_inputMessageQueue.pop()) != 0)
     {
-        qDebug("FileSourceGui::handleInputMessages: message: %s", message->getIdentifier());
-
         if (DSPSignalNotification::match(*message))
         {
             DSPSignalNotification* notif = (DSPSignalNotification*) message;
diff --git a/sdrbase/dsp/dspengine.cpp b/sdrbase/dsp/dspengine.cpp
index 67c93c9d6..524b57c4e 100644
--- a/sdrbase/dsp/dspengine.cpp
+++ b/sdrbase/dsp/dspengine.cpp
@@ -231,9 +231,15 @@ void DSPEngine::getDVSerialNames(std::vector<std::string>& deviceNames __attribu
 #endif
 
 #ifdef DSD_USE_SERIALDV
-void DSPEngine::pushMbeFrame(const unsigned char *mbeFrame, int mbeRateIndex, int mbeVolumeIndex, unsigned char channels, AudioFifo *audioFifo)
+void DSPEngine::pushMbeFrame(
+        const unsigned char *mbeFrame,
+        int mbeRateIndex,
+        int mbeVolumeIndex,
+        unsigned char channels,
+        bool useHP,
+        AudioFifo *audioFifo)
 {
-    m_dvSerialEngine.pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, audioFifo);
+    m_dvSerialEngine.pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, useHP, audioFifo);
 }
 #else
 void DSPEngine::pushMbeFrame(
@@ -241,6 +247,7 @@ void DSPEngine::pushMbeFrame(
         int mbeRateIndex __attribute((unused)),
         int mbeVolumeIndex __attribute((unused)),
         unsigned char channels __attribute((unused)),
+        bool useHP __attribute((unused)),
         AudioFifo *audioFifo __attribute((unused)))
 {}
 #endif
diff --git a/sdrbase/dsp/dspengine.h b/sdrbase/dsp/dspengine.h
index 144b3dbb0..7f8bac5b1 100644
--- a/sdrbase/dsp/dspengine.h
+++ b/sdrbase/dsp/dspengine.h
@@ -78,7 +78,13 @@ public:
 	bool hasDVSerialSupport();
 	void setDVSerialSupport(bool support);
 	void getDVSerialNames(std::vector<std::string>& deviceNames);
-	void pushMbeFrame(const unsigned char *mbeFrame, int mbeRateIndex, int mbeVolumeIndex, unsigned char channels, AudioFifo *audioFifo);
+	void pushMbeFrame(
+	        const unsigned char *mbeFrame,
+	        int mbeRateIndex,
+	        int mbeVolumeIndex,
+	        unsigned char channels,
+	        bool useHP,
+	        AudioFifo *audioFifo);
 
     const QTimer& getMasterTimer() const { return m_masterTimer; }
 
diff --git a/sdrbase/dsp/dvserialengine.cpp b/sdrbase/dsp/dvserialengine.cpp
index 73ef225b8..d042a2019 100644
--- a/sdrbase/dsp/dvserialengine.cpp
+++ b/sdrbase/dsp/dvserialengine.cpp
@@ -247,7 +247,13 @@ void DVSerialEngine::getDevicesNames(std::vector<std::string>& deviceNames)
     }
 }
 
-void DVSerialEngine::pushMbeFrame(const unsigned char *mbeFrame, int mbeRateIndex, int mbeVolumeIndex, unsigned char channels, AudioFifo *audioFifo)
+void DVSerialEngine::pushMbeFrame(
+        const unsigned char *mbeFrame,
+        int mbeRateIndex,
+        int mbeVolumeIndex,
+        unsigned char channels,
+        bool useLP,
+        AudioFifo *audioFifo)
 {
     std::vector<DVSerialController>::iterator it = m_controllers.begin();
     std::vector<DVSerialController>::iterator itAvail = m_controllers.end();
@@ -258,7 +264,7 @@ void DVSerialEngine::pushMbeFrame(const unsigned char *mbeFrame, int mbeRateInde
     {
         if (it->worker->hasFifo(audioFifo))
         {
-            it->worker->pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, audioFifo);
+            it->worker->pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, useLP, audioFifo);
             done = true;
         }
         else if (it->worker->isAvailable())
@@ -276,7 +282,7 @@ void DVSerialEngine::pushMbeFrame(const unsigned char *mbeFrame, int mbeRateInde
             int wNum = itAvail - m_controllers.begin();
 
             qDebug("DVSerialEngine::pushMbeFrame: push %p on empty queue %d", audioFifo, wNum);
-            itAvail->worker->pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, audioFifo);
+            itAvail->worker->pushMbeFrame(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, useLP, audioFifo);
         }
         else
         {
diff --git a/sdrbase/dsp/dvserialengine.h b/sdrbase/dsp/dvserialengine.h
index 5b7c621ba..f2248f90e 100644
--- a/sdrbase/dsp/dvserialengine.h
+++ b/sdrbase/dsp/dvserialengine.h
@@ -41,7 +41,13 @@ public:
     int getNbDevices() const { return m_controllers.size(); }
     void getDevicesNames(std::vector<std::string>& devicesNames);
 
-    void pushMbeFrame(const unsigned char *mbeFrame, int mbeRateIndex, int mbeVolumeIndex, unsigned char channels, AudioFifo *audioFifo);
+    void pushMbeFrame(
+            const unsigned char *mbeFrame,
+            int mbeRateIndex,
+            int mbeVolumeIndex,
+            unsigned char channels,
+            bool useHP,
+            AudioFifo *audioFifo);
 
 private:
     struct DVSerialController
diff --git a/sdrbase/dsp/dvserialworker.cpp b/sdrbase/dsp/dvserialworker.cpp
index 6d2b40990..8db6935a5 100644
--- a/sdrbase/dsp/dvserialworker.cpp
+++ b/sdrbase/dsp/dvserialworker.cpp
@@ -81,6 +81,8 @@ void DVSerialWorker::handleInputMessages()
             MsgMbeDecode *decodeMsg = (MsgMbeDecode *) message;
             int dBVolume = (decodeMsg->getVolumeIndex() - 30) / 2;
 
+            m_upsampleFilter.useHP(decodeMsg->getUseHP());
+
             if (m_dvController.decode(m_dvAudioSamples, decodeMsg->getMbeFrame(), decodeMsg->getMbeRate(), dBVolume))
             {
                 upsample6(m_dvAudioSamples, SerialDV::MBE_AUDIO_BLOCK_SIZE, decodeMsg->getChannels());
@@ -111,10 +113,12 @@ void DVSerialWorker::handleInputMessages()
 void DVSerialWorker::pushMbeFrame(const unsigned char *mbeFrame,
         int mbeRateIndex,
         int mbeVolumeIndex,
-        unsigned char channels, AudioFifo *audioFifo)
+        unsigned char channels,
+        bool useHP,
+        AudioFifo *audioFifo)
 {
     m_audioFifo = audioFifo;
-    m_inputMessageQueue.push(MsgMbeDecode::create(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, audioFifo));
+    m_inputMessageQueue.push(MsgMbeDecode::create(mbeFrame, mbeRateIndex, mbeVolumeIndex, channels, useHP, audioFifo));
 }
 
 bool DVSerialWorker::isAvailable()
diff --git a/sdrbase/dsp/dvserialworker.h b/sdrbase/dsp/dvserialworker.h
index a79037770..da7347037 100644
--- a/sdrbase/dsp/dvserialworker.h
+++ b/sdrbase/dsp/dvserialworker.h
@@ -54,11 +54,18 @@ public:
         SerialDV::DVRate getMbeRate() const { return m_mbeRate; }
         int getVolumeIndex() const { return m_volumeIndex; }
         unsigned char getChannels() const { return m_channels % 4; }
+        bool getUseHP() const { return m_useHP; }
         AudioFifo *getAudioFifo() { return m_audioFifo; }
 
-        static MsgMbeDecode* create(const unsigned char *mbeFrame, int mbeRateIndex, int volumeIndex, unsigned char channels, AudioFifo *audioFifo)
+        static MsgMbeDecode* create(
+                const unsigned char *mbeFrame,
+                int mbeRateIndex,
+                int volumeIndex,
+                unsigned char channels,
+                bool useHP,
+                AudioFifo *audioFifo)
         {
-            return new MsgMbeDecode(mbeFrame, (SerialDV::DVRate) mbeRateIndex, volumeIndex, channels, audioFifo);
+            return new MsgMbeDecode(mbeFrame, (SerialDV::DVRate) mbeRateIndex, volumeIndex, channels, useHP, audioFifo);
         }
 
     private:
@@ -66,17 +73,20 @@ public:
         SerialDV::DVRate m_mbeRate;
         int m_volumeIndex;
         unsigned char m_channels;
+        bool m_useHP;
         AudioFifo *m_audioFifo;
 
         MsgMbeDecode(const unsigned char *mbeFrame,
                 SerialDV::DVRate mbeRate,
                 int volumeIndex,
                 unsigned char channels,
+                bool useHP,
                 AudioFifo *audioFifo) :
             Message(),
             m_mbeRate(mbeRate),
             m_volumeIndex(volumeIndex),
             m_channels(channels),
+            m_useHP(useHP),
             m_audioFifo(audioFifo)
         {
             memcpy((void *) m_mbeFrame, (const void *) mbeFrame, SerialDV::DVController::getNbMbeBytes(m_mbeRate));
@@ -90,6 +100,7 @@ public:
             int mbeRateIndex,
             int mbeVolumeIndex,
             unsigned char channels,
+            bool useHP,
             AudioFifo *audioFifo);
 
     bool open(const std::string& serialDevice);
diff --git a/sdrbase/dsp/filtermbe.cpp b/sdrbase/dsp/filtermbe.cpp
index a4b5b0f85..2ce391587 100644
--- a/sdrbase/dsp/filtermbe.cpp
+++ b/sdrbase/dsp/filtermbe.cpp
@@ -17,40 +17,23 @@
 
 #include "filtermbe.h"
 
-const float MBEAudioInterpolatorFilter::m_a0 = 3.869430E-02;
-const float MBEAudioInterpolatorFilter::m_a1 = 7.738860E-02;
-const float MBEAudioInterpolatorFilter::m_a2 = 3.869430E-02;
-const float MBEAudioInterpolatorFilter::m_b1 = 1.392667E+00;
-const float MBEAudioInterpolatorFilter::m_b2 = -5.474446E-01;
+const float MBEAudioInterpolatorFilter::m_lpa[3] = {1.0,           1.392667E+00, -5.474446E-01};
+const float MBEAudioInterpolatorFilter::m_lpb[3] = {3.869430E-02,  7.738860E-02,  3.869430E-02};
 
-MBEAudioInterpolatorFilter::MBEAudioInterpolatorFilter()
+const float MBEAudioInterpolatorFilter::m_hpa[3] = {1.000000e+00,  1.911437E+00, -9.155749E-01};
+const float MBEAudioInterpolatorFilter::m_hpb[3] = {9.567529E-01, -1.913506E+00,  9.567529E-01};
+
+MBEAudioInterpolatorFilter::MBEAudioInterpolatorFilter() :
+        m_filterLP(m_lpa, m_lpb),
+        m_filterHP(m_hpa, m_hpb),
+        m_useHP(false)
 {
-    init();
 }
 
 MBEAudioInterpolatorFilter::~MBEAudioInterpolatorFilter()
 {}
 
-void MBEAudioInterpolatorFilter::init()
+float MBEAudioInterpolatorFilter::run(const float& sample)
 {
-    m_x[0] = 0.0f;
-    m_x[1] = 0.0f;
-    m_y[0] = 0.0f;
-    m_y[1] = 0.0f;
+    return m_useHP ? m_filterLP.run(m_filterHP.run(sample)) : m_filterLP.run(sample);
 }
-
-float MBEAudioInterpolatorFilter::run(float sample)
-{
-    float y = m_a0*sample + m_a1*m_x[0] + m_a2*m_x[1] + m_b1*m_y[0] + m_b2*m_y[1]; // this is y[n]
-
-    m_x[1] = m_x[0];
-    m_x[0] = sample;
-
-    m_y[1] = m_y[0];
-    m_y[0] = y;
-
-    return y;
-}
-
-
-
diff --git a/sdrbase/dsp/filtermbe.h b/sdrbase/dsp/filtermbe.h
index 5f3f3239b..f3d6788fb 100644
--- a/sdrbase/dsp/filtermbe.h
+++ b/sdrbase/dsp/filtermbe.h
@@ -19,35 +19,61 @@
 #define SDRBASE_DSP_FILTERMBE_H_
 
 /**
- * This is a 2 pole lowpass Chebyshev (recursive) filter at fc=0.075 using coefficients found in table 20-1 of
- * http://www.analog.com/media/en/technical-documentation/dsp-book/dsp_book_Ch20.pdf
+ * Uses the generic IIR filter internally
+ *
+ * Low pass / High pass:
+ *
+ * This is a 2 pole Chebyshev (recursive) filter using coefficients found in table 20-1 (low pass)
+ * or table 20-2 (high pass) of http://www.analog.com/media/en/technical-documentation/dsp-book/dsp_book_Ch20.pdf
+ *
+ * For low pass fc = 0.075
+ * For high oass fc = 0.01
+ *
+ * Convention taken here exchanges A and B coefficients as shown in this image:
+ * https://cdn.mikroe.com/ebooks/img/8/2016/02/digital-filter-design-chapter-03-image-2-9.gif
+ * So A applies to Y and B to X
  *
  * At the interpolated sampling frequency of 48 kHz the -3 dB corner is at 48 * .075 = 3.6 kHz which is perfect for voice
+ * The high pass has a 3 dB corner of 48 * 0.01 = 0.48 kHz
  *
- * a0= 3.869430E-02
- * a1= 7.738860E-02 b1= 1.392667E+00
- * a2= 3.869430E-02 b2= -5.474446E-01
+ * Low pass:
+ *
+ * b0 = 3.869430E-02 (a0 = 1.0)
+ * b1 = 7.738860E-02 a1 =  1.392667E+00
+ * b2 = 3.869430E-02 a2 = -5.474446E-01
+ *
+ * High pass:
+ *
+ * b0 =  9.567529E-01 (a0 = 1.0)
+ * b1 = -1.913506E+00  a1 =  1.911437E+00
+ * b2 =  9.567529E-01  a2 = -9.155749E-01
  *
  * given x[n] is the new input sample and y[n] the returned output sample:
  *
- * y[n] = a0*x[n] + a1*x[n] + a2*x[n] + b1*y[n-1] + b2*y[n-2]
+ * y[n] = b0*x[n] + b1*x[n] + b2*x[n] + a1*y[n-1] + a2*y[n-2]
  *
  * This one works directly with floats
  *
+ *
  */
+
+#include "iirfilter.h"
+
 class MBEAudioInterpolatorFilter
 {
 public:
     MBEAudioInterpolatorFilter();
     ~MBEAudioInterpolatorFilter();
 
-    void init();
-    float run(float sample);
+    void useHP(bool useHP) { m_useHP = useHP; }
+    float run(const float& sample);
 
 private:
-    float m_x[2];
-    float m_y[2];
-    static const float m_a0, m_a1, m_a2, m_b1, m_b2;
+    IIRFilter<float, 2> m_filterLP;
+    IIRFilter<float, 2> m_filterHP;
+    bool m_useHP;
+    static const float m_lpa[3], m_lpb[3]; // low pass coefficients
+    static const float m_hpa[3], m_hpb[3]; // band pass coefficients
 };
 
 
diff --git a/sdrbase/dsp/iirfilter.h b/sdrbase/dsp/iirfilter.h
index c29571171..18480c531 100644
--- a/sdrbase/dsp/iirfilter.h
+++ b/sdrbase/dsp/iirfilter.h
@@ -15,10 +15,16 @@
 // along with this program. If not, see <http://www.gnu.org/licenses/>.          //
 ///////////////////////////////////////////////////////////////////////////////////
 
+/**
+ * IIR filter
+ * See: https://cdn.mikroe.com/ebooks/img/8/2016/02/digital-filter-design-chapter-03-image-2-9.gif
+ */
+
 #ifndef SDRBASE_DSP_IIRFILTER_H_
 #define SDRBASE_DSP_IIRFILTER_H_
 
 #include <stdint.h>
+#include <string.h>
 #include <assert.h>
 
 template <typename Type, uint32_t Order> class IIRFilter
@@ -26,7 +32,8 @@ template <typename Type, uint32_t Order> class IIRFilter
 public:
     IIRFilter(const Type *a, const Type *b);
     ~IIRFilter();
-    Type run(Type sample);
+    void setCoeffs(const Type *a, const Type *b);
+    Type run(const Type& sample);
 
 private:
     Type *m_a;
@@ -40,7 +47,8 @@ template <typename Type> class IIRFilter<Type, 2>
 public:
     IIRFilter(const Type *a, const Type *b);
     ~IIRFilter();
-    Type run(Type sample);
+    void setCoeffs(const Type *a, const Type *b);
+    Type run(const Type& sample);
 
 private:
     Type m_a[3];
@@ -59,14 +67,7 @@ IIRFilter<Type, Order>::IIRFilter(const Type *a, const Type *b)
     m_x = new Type[Order];
     m_y = new Type[Order];
 
-    memcpy(m_a, a, (Order+1)*sizeof(Type));
-    memcpy(m_b, b, (Order+1)*sizeof(Type));
-
-    for (int i = 0; i < Order; i++)
-    {
-        m_x[i] = 0;
-        m_y[i] = 0;
-    }
+    setCoeffs(a, b);
 }
 
 template <typename Type, uint32_t Order>
@@ -79,30 +80,47 @@ IIRFilter<Type, Order>::~IIRFilter()
 }
 
 template <typename Type, uint32_t Order>
-Type IIRFilter<Type, Order>::run(Type sample)
+void IIRFilter<Type, Order>::setCoeffs(const Type *a, const Type *b)
 {
-    Type y = m_a[0] * sample;
+    memcpy(m_a, b, (Order+1)*sizeof(Type));
+    memcpy(m_b, a, (Order+1)*sizeof(Type));
 
-    for (int i = 0; i < Order; i++)
+    for (uint32_t i = 0; i < Order; i++)
     {
-        y += m_a[i+1] * m_x[i] + m_b[i+1] * m_y[i];
+        m_x[i] = 0;
+        m_y[i] = 0;
+    }
+}
+
+
+template <typename Type, uint32_t Order>
+Type IIRFilter<Type, Order>::run(const Type& sample)
+{
+    Type y = m_b[0] * sample;
+
+    for (uint32_t i = Order; i > 0; i--)
+    {
+        y += m_b[i] * m_x[i-1] + m_a[i] * m_y[i-1];
+
+        if (i > 1) // shift
+        {
+            m_x[i-1] = m_x[i-2];
+            m_y[i-1] = m_y[i-2];
+        }
     }
 
+    // last shift
     m_x[0] = sample;
     m_y[0] = y;
 
-    memcpy(&m_x[1], &m_x[0], (Order-1)*sizeof(Type));
+    return y;
 }
 
+
 template <typename Type>
 IIRFilter<Type, 2>::IIRFilter(const Type *a, const Type *b)
 {
-    m_a[0] = a[0];
-    m_a[1] = a[1];
-    m_a[2] = a[2];
-    m_b[0] = b[0];
-    m_b[1] = b[1];
-    m_b[2] = b[2];
+    setCoeffs(a, b);
 }
 
 template <typename Type>
@@ -111,9 +129,24 @@ IIRFilter<Type, 2>::~IIRFilter()
 }
 
 template <typename Type>
-Type IIRFilter<Type, 2>::run(Type sample)
+void IIRFilter<Type, 2>::setCoeffs(const Type *a, const Type *b)
 {
-    Type y = m_a[0]*sample + m_a[1]*m_x[0] + m_a[2]*m_x[1] + m_b[1]*m_y[0] + m_b[2]*m_y[1]; // this is y[n]
+    m_a[0] = a[0];
+    m_a[1] = a[1];
+    m_a[2] = a[2];
+    m_b[0] = b[0];
+    m_b[1] = b[1];
+    m_b[2] = b[2];
+    m_x[0] = 0;
+    m_x[1] = 0;
+    m_y[0] = 0;
+    m_y[1] = 0;
+}
+
+template <typename Type>
+Type IIRFilter<Type, 2>::run(const Type& sample)
+{
+    Type y = m_b[0]*sample + m_b[1]*m_x[0] + m_b[2]*m_x[1] + m_a[1]*m_y[0] + m_a[2]*m_y[1]; // this is y[n]
 
     m_x[1] = m_x[0];
     m_x[0] = sample;