diff --git a/src/engine/platform/sound/su.cpp b/src/engine/platform/sound/su.cpp
index a2fd7653..6637bfa7 100644
--- a/src/engine/platform/sound/su.cpp
+++ b/src/engine/platform/sound/su.cpp
@@ -238,44 +238,65 @@ void SoundUnit::NextSample(short* l, short* r) {
   tnsL=(nsL[0]+nsL[1]+nsL[2]+nsL[3]+nsL[4]+nsL[5]+nsL[6]+nsL[7])>>2;
   tnsR=(nsR[0]+nsR[1]+nsR[2]+nsR[3]+nsR[4]+nsR[5]+nsR[6]+nsR[7])>>2;
 
+  IL1=minval(32767,maxval(-32767,tnsL))>>8;
+  IL2=minval(32767,maxval(-32767,tnsR))>>8;
+
   // write input lines to sample memory
   if (ILSIZE&64) {
     if (++ilBufPeriod>=((1+(FIL1>>4))<<2)) {
       ilBufPeriod=0;
       unsigned short ilLowerBound=pcmSize-((1+(ILSIZE&63))<<7);
+      short next;
       if (ilBufPos<ilLowerBound) ilBufPos=ilLowerBound;
       switch (ILCTRL&3) {
         case 0:
           ilFeedback0=ilFeedback1=pcm[ilBufPos];
-          pcm[ilBufPos]=IL0+((pcm[ilBufPos]*(FIL1&15))>>4);
+          next=((signed char)IL0)+((pcm[ilBufPos]*(FIL1&15))>>4);
+          if (next<-128) next=-128;
+          if (next>127) next=127;
+          pcm[ilBufPos]=next;
           if (++ilBufPos>=pcmSize) ilBufPos=ilLowerBound;
           break;
         case 1:
           ilFeedback0=ilFeedback1=pcm[ilBufPos];
-          pcm[ilBufPos]=IL1+((pcm[ilBufPos]*(FIL1&15))>>4);
+          next=((signed char)IL1)+((pcm[ilBufPos]*(FIL1&15))>>4);
+          if (next<-128) next=-128;
+          if (next>127) next=127;
+          pcm[ilBufPos]=next;
           if (++ilBufPos>=pcmSize) ilBufPos=ilLowerBound;
           break;
         case 2:
           ilFeedback0=ilFeedback1=pcm[ilBufPos];
-          pcm[ilBufPos]=IL2+((pcm[ilBufPos]*(FIL1&15))>>4);
+          next=((signed char)IL2)+((pcm[ilBufPos]*(FIL1&15))>>4);
+          if (next<-128) next=-128;
+          if (next>127) next=127;
+          pcm[ilBufPos]=next;
           if (++ilBufPos>=pcmSize) ilBufPos=ilLowerBound;
           break;
         case 3:
           ilFeedback0=pcm[ilBufPos];
-          pcm[ilBufPos]=IL1+((pcm[ilBufPos]*(FIL1&15))>>4);
+          next=((signed char)IL1)+((pcm[ilBufPos]*(FIL1&15))>>4);
+          if (next<-128) next=-128;
+          if (next>127) next=127;
+          pcm[ilBufPos]=next;
           if (++ilBufPos>=pcmSize) ilBufPos=ilLowerBound;
           ilFeedback1=pcm[ilBufPos];
-          pcm[ilBufPos]=IL2+((pcm[ilBufPos]*(FIL1&15))>>4);
+          next=((signed char)IL2)+((pcm[ilBufPos]*(FIL1&15))>>4);
+          if (next<-128) next=-128;
+          if (next>127) next=127;
+          pcm[ilBufPos]=next;
           if (++ilBufPos>=pcmSize) ilBufPos=ilLowerBound;
           break;
       }
     }
-    if (ILSIZE&128) {
-      tnsL+=ilFeedback1*(signed char)FILVOL;
-      tnsR+=ilFeedback0*(signed char)FILVOL;
-    } else {
-      tnsL+=ilFeedback0*(signed char)FILVOL;
-      tnsR+=ilFeedback1*(signed char)FILVOL;
+    if (ILCTRL&4) {
+      if (ILSIZE&128) {
+        tnsL+=ilFeedback1*(signed char)FILVOL;
+        tnsR+=ilFeedback0*(signed char)FILVOL;
+      } else {
+        tnsL+=ilFeedback0*(signed char)FILVOL;
+        tnsR+=ilFeedback1*(signed char)FILVOL;
+      }
     }
   }
 
diff --git a/src/engine/platform/su.cpp b/src/engine/platform/su.cpp
index 4320798a..6c6b0b32 100644
--- a/src/engine/platform/su.cpp
+++ b/src/engine/platform/su.cpp
@@ -529,6 +529,16 @@ void DivPlatformSoundUnit::reset() {
   lfoMode=0;
   lfoSpeed=255;
   delay=500;
+
+  // set initial IL status
+  ilCtrl=initIlCtrl;
+  ilSize=initIlSize;
+  fil1=initFil1;
+  echoVol=initEchoVol;
+  rWrite(0x9c,echoVol);
+  rWrite(0x9d,ilCtrl);
+  rWrite(0xbc,ilSize);
+  rWrite(0xbd,fil1);
 }
 
 bool DivPlatformSoundUnit::isStereo() {
@@ -555,6 +565,10 @@ void DivPlatformSoundUnit::setFlags(unsigned int flags) {
   for (int i=0; i<8; i++) {
     oscBuf[i]->rate=rate;
   }
+  initIlCtrl=3|(flags&4);
+  initIlSize=((flags>>8)&63)|((flags&4)?0x40:0)|((flags&8)?0x80:0);
+  initFil1=flags>>16;
+  initEchoVol=flags>>24;
 
   sampleMemSize=flags&16;
 
@@ -575,7 +589,7 @@ const void* DivPlatformSoundUnit::getSampleMem(int index) {
 }
 
 size_t DivPlatformSoundUnit::getSampleMemCapacity(int index) {
-  return (index==0)?(sampleMemSize?65536:8192):0;
+  return (index==0)?((sampleMemSize?65536:8192)-((initIlSize&64)?((1+(initIlSize&63))<<7):0)):0;
 }
 
 size_t DivPlatformSoundUnit::getSampleMemUsage(int index) {
diff --git a/src/engine/platform/su.h b/src/engine/platform/su.h
index e882c398..9972599d 100644
--- a/src/engine/platform/su.h
+++ b/src/engine/platform/su.h
@@ -97,6 +97,9 @@ class DivPlatformSoundUnit: public DivDispatch {
   std::queue<QueuedWrite> writes;
   unsigned char lastPan;
   bool sampleMemSize;
+  unsigned char ilCtrl, ilSize, fil1;
+  unsigned char initIlCtrl, initIlSize, initFil1;
+  signed char echoVol, initEchoVol;
 
   int cycles, curChan, delay;
   short tempL;
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index 4cc1784a..3259f00c 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -129,11 +129,11 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
     }
     case DIV_SYSTEM_SOUND_UNIT: {
       ImGui::Text("CPU rate:");
-      if (ImGui::RadioButton("6.18MHz (NTSC)",(flags&15)==0)) {
-        copyOfFlags=(flags&(~15))|0;
+      if (ImGui::RadioButton("6.18MHz (NTSC)",(flags&3)==0)) {
+        copyOfFlags=(flags&(~3))|0;
       }
-      if (ImGui::RadioButton("5.95MHz (PAL)",(flags&15)==1)) {
-        copyOfFlags=(flags&(~15))|1;
+      if (ImGui::RadioButton("5.95MHz (PAL)",(flags&3)==1)) {
+        copyOfFlags=(flags&(~3))|1;
       }
       ImGui::Text("Chip revision (sample memory):");
       if (ImGui::RadioButton("A/B/E (8K)",(flags&16)==0)) {
@@ -142,6 +142,42 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
       if (ImGui::RadioButton("D/F (64K)",(flags&16)==16)) {
         copyOfFlags=(flags&(~16))|16;
       }
+      bool echo=flags&4;
+      if (ImGui::Checkbox("Enable echo",&echo)) {
+        copyOfFlags=(flags&(~4))|(echo<<2);
+      }
+      bool flipEcho=flags&8;
+      if (ImGui::Checkbox("Swap echo channels",&flipEcho)) {
+        copyOfFlags=(flags&(~8))|(flipEcho<<3);
+      }
+      ImGui::Text("Echo delay:");
+      int echoBufSize=(flags&0x3f00)>>8;
+      if (CWSliderInt("##EchoBufSize",&echoBufSize,0,63)) {
+        if (echoBufSize<0) echoBufSize=0;
+        if (echoBufSize>63) echoBufSize=63;
+        copyOfFlags=(flags&~0x3f00)|(echoBufSize<<8);
+      } rightClickable
+      ImGui::Text("Echo resolution:");
+      int echoResolution=(flags&0xf00000)>>20;
+      if (CWSliderInt("##EchoResolution",&echoResolution,0,15)) {
+        if (echoResolution<0) echoResolution=0;
+        if (echoResolution>15) echoResolution=15;
+        copyOfFlags=(flags&(~0xf00000))|(echoResolution<<20);
+      } rightClickable
+      ImGui::Text("Echo feedback:");
+      int echoFeedback=(flags&0xf0000)>>16;
+      if (CWSliderInt("##EchoFeedback",&echoFeedback,0,15)) {
+        if (echoFeedback<0) echoFeedback=0;
+        if (echoFeedback>15) echoFeedback=15;
+        copyOfFlags=(flags&(~0xf0000))|(echoFeedback<<16);
+      } rightClickable
+      ImGui::Text("Echo volume:");
+      int echoVolume=(signed char)((flags&0xff000000)>>24);
+      if (CWSliderInt("##EchoVolume",&echoVolume,-128,127)) {
+        if (echoVolume<-128) echoVolume=-128;
+        if (echoVolume>127) echoVolume=127;
+        copyOfFlags=(flags&(~0xff000000))|(((unsigned char)echoVolume)<<24);
+      } rightClickable
       break;
     }
     case DIV_SYSTEM_GB: {