diff --git a/papers/format.md b/papers/format.md
index ca8092a5a..97e22a4e5 100644
--- a/papers/format.md
+++ b/papers/format.md
@@ -810,6 +810,9 @@ size | description
   1  | vib depth
   1  | am depth
  23  | reserved
+ --- | **Sound Unit data** (>=104)
+  1  | use sample
+  1  | switch roles of phase reset timer and frequency
 ```
 
 # wavetable
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 6f969efc9..256b0c96d 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -45,8 +45,8 @@
 #define BUSY_BEGIN_SOFT softLocked=true; isBusy.lock();
 #define BUSY_END isBusy.unlock(); softLocked=false;
 
-#define DIV_VERSION "dev103"
-#define DIV_ENGINE_VERSION 103
+#define DIV_VERSION "dev104"
+#define DIV_ENGINE_VERSION 104
 
 // for imports
 #define DIV_VERSION_MOD 0xff01
diff --git a/src/engine/instrument.cpp b/src/engine/instrument.cpp
index a76588561..4d274e18c 100644
--- a/src/engine/instrument.cpp
+++ b/src/engine/instrument.cpp
@@ -528,6 +528,10 @@ void DivInstrument::putInsData(SafeWriter* w) {
     w->writeC(0);
   }
 
+  // Sound Unit
+  w->writeC(su.useSample);
+  w->writeC(su.switchRoles);
+
   blockEndSeek=w->tell();
   w->seek(blockStartSeek,SEEK_SET);
   w->writeI(blockEndSeek-blockStartSeek-4);
@@ -1075,6 +1079,12 @@ DivDataErrors DivInstrument::readInsData(SafeReader& reader, short version) {
     for (int k=0; k<23; k++) reader.readC();
   }
 
+  // Sound Unit
+  if (version>=104) {
+    su.useSample=reader.readC();
+    su.switchRoles=reader.readC();
+  }
+
   return DIV_DATA_SUCCESS;
 }
 
diff --git a/src/engine/instrument.h b/src/engine/instrument.h
index 18bf2c5f7..1c25988e4 100644
--- a/src/engine/instrument.h
+++ b/src/engine/instrument.h
@@ -437,6 +437,14 @@ struct DivInstrumentWaveSynth {
     param4(0) {}
 };
 
+struct DivInstrumentSoundUnit {
+  bool useSample;
+  bool switchRoles;
+  DivInstrumentSoundUnit():
+    useSample(false),
+    switchRoles(false) {}
+};
+
 struct DivInstrument {
   String name;
   bool mode;
@@ -450,6 +458,7 @@ struct DivInstrument {
   DivInstrumentFDS fds;
   DivInstrumentMultiPCM multipcm;
   DivInstrumentWaveSynth ws;
+  DivInstrumentSoundUnit su;
   
   /**
    * save the instrument to a SafeWriter.
diff --git a/src/engine/platform/su.cpp b/src/engine/platform/su.cpp
index 2d1a38932..4320798ab 100644
--- a/src/engine/platform/su.cpp
+++ b/src/engine/platform/su.cpp
@@ -256,12 +256,12 @@ int DivPlatformSoundUnit::dispatch(DivCommand c) {
   switch (c.cmd) {
     case DIV_CMD_NOTE_ON: {
       DivInstrument* ins=parent->getIns(chan[c.chan].ins,DIV_INS_SU);
-      if (chan[c.chan].pcm && ins->type!=DIV_INS_AMIGA) {
-        chan[c.chan].pcm=(ins->type==DIV_INS_AMIGA);
+      if (chan[c.chan].pcm && !(ins->type==DIV_INS_AMIGA || ins->su.useSample)) {
+        chan[c.chan].pcm=(ins->type==DIV_INS_AMIGA || ins->su.useSample);
         writeControl(c.chan);
         writeControlUpper(c.chan);
       }
-      chan[c.chan].pcm=(ins->type==DIV_INS_AMIGA);
+      chan[c.chan].pcm=(ins->type==DIV_INS_AMIGA || ins->su.useSample);
       if (c.value!=DIV_NOTE_NULL) {
         chan[c.chan].baseFreq=NOTE_FREQUENCY(c.value);
         chan[c.chan].freqChanged=true;
diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index f991b9e2a..8e405251e 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -3093,13 +3093,17 @@ void FurnaceGUI::drawInsEdit() {
           P(ImGui::Checkbox("Don't test/gate before new note",&ins->c64.noTest));
           ImGui::EndTabItem();
         }
-        if (ins->type==DIV_INS_AMIGA) if (ImGui::BeginTabItem("Sample")) {
+        if (ins->type==DIV_INS_AMIGA || ins->type==DIV_INS_SU) if (ImGui::BeginTabItem((ins->type==DIV_INS_SU)?"Sound Unit":"Sample")) {
           String sName;
           if (ins->amiga.initSample<0 || ins->amiga.initSample>=e->song.sampleLen) {
             sName="none selected";
           } else {
             sName=e->song.sample[ins->amiga.initSample]->name;
           }
+          if (ins->type==DIV_INS_SU) {
+            P(ImGui::Checkbox("Use sample",&ins->su.useSample));
+            P(ImGui::Checkbox("Switch roles of frequency and phase reset timer",&ins->su.switchRoles));
+          }
           if (ImGui::BeginCombo("Initial Sample",sName.c_str())) {
             String id;
             for (int i=0; i<e->song.sampleLen; i++) {
@@ -3110,14 +3114,16 @@ void FurnaceGUI::drawInsEdit() {
             }
             ImGui::EndCombo();
           }
-          P(ImGui::Checkbox("Use wavetable (Amiga only)",&ins->amiga.useWave));
-          if (ins->amiga.useWave) {
-            int len=ins->amiga.waveLen+1;
-            if (ImGui::InputInt("Width",&len,2,16)) {
-              if (len<2) len=2;
-              if (len>256) len=256;
-              ins->amiga.waveLen=(len&(~1))-1;
-              PARAMETER
+          if (ins->type==DIV_INS_AMIGA) {
+            P(ImGui::Checkbox("Use wavetable (Amiga only)",&ins->amiga.useWave));
+            if (ins->amiga.useWave) {
+              int len=ins->amiga.waveLen+1;
+              if (ImGui::InputInt("Width",&len,2,16)) {
+                if (len<2) len=2;
+                if (len>256) len=256;
+                ins->amiga.waveLen=(len&(~1))-1;
+                PARAMETER
+              }
             }
           }
           ImGui::BeginDisabled(ins->amiga.useWave);