diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index e8bfb48b2..d2630aca4 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -5443,6 +5443,7 @@ FurnaceGUI::FurnaceGUI():
   displayPendingIns(false),
   pendingInsSingle(false),
   displayPendingRawSample(false),
+  snesFilterHex(false),
   vgmExportVersion(0x171),
   drawHalt(10),
   zsmExportTickRate(60),
diff --git a/src/gui/gui.h b/src/gui/gui.h
index e20656f7a..30a97a684 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -1039,7 +1039,7 @@ class FurnaceGUI {
   bool portrait, mobileMenuOpen;
   bool wantCaptureKeyboard, oldWantCaptureKeyboard, displayMacroMenu;
   bool displayNew, fullScreen, preserveChanPos, wantScrollList, noteInputPoly;
-  bool displayPendingIns, pendingInsSingle, displayPendingRawSample;
+  bool displayPendingIns, pendingInsSingle, displayPendingRawSample, snesFilterHex;
   bool willExport[32];
   int vgmExportVersion;
   int drawHalt;
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index 1b793a2fb..967624a5d 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -19,6 +19,7 @@
 
 #include "gui.h"
 #include "misc/cpp/imgui_stdlib.h"
+#include <imgui.h>
 
 bool FurnaceGUI::drawSysConf(int chan, DivSystem type, DivConfig& flags, bool modifyOnChange) {
   bool altered=false;
@@ -1273,19 +1274,51 @@ bool FurnaceGUI::drawSysConf(int chan, DivSystem type, DivConfig& flags, bool mo
         } rightClickable
       }
 
+      if (ImGui::Button(snesFilterHex?"Hex##SNESFHex":"Dec##SNESFHex")) {
+        snesFilterHex=!snesFilterHex;
+      }
+      ImGui::SameLine();
       ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x); // wavetable text input size found here
       if (ImGui::InputText("##MMLWave",&mmlStringSNES)) {
         int actualData[256];
         int discardIt=0;
         memset(actualData,0,256*sizeof(int));
-        decodeMMLStrW(mmlStringSNES,actualData,discardIt,-128,127,false);
+        decodeMMLStrW(mmlStringSNES,actualData,discardIt,snesFilterHex?0:-128,snesFilterHex?255:127,snesFilterHex);
+        if (snesFilterHex) {
+          for (int i=0; i<8; i++) {
+            if (actualData[i]>=128) actualData[i]-=256;
+          }
+        }
         memcpy(echoFilter,actualData,8*sizeof(int));
         altered=true;
       }
       if (!ImGui::IsItemActive()) {
-        encodeMMLStr(mmlStringSNES,echoFilter,8,-1,-1,false);
+        int actualData[8];
+        for (int i=0; i<8; i++) {
+          if (echoFilter[i]<0 && snesFilterHex) {
+            actualData[i]=echoFilter[i]+256;
+          } else {
+            actualData[i]=echoFilter[i];
+          }
+        }
+        encodeMMLStr(mmlStringSNES,actualData,8,-1,-1,snesFilterHex);
       }
 
+      int filterSum=(
+        echoFilter[0]+
+        echoFilter[1]+
+        echoFilter[2]+
+        echoFilter[3]+
+        echoFilter[4]+
+        echoFilter[5]+
+        echoFilter[6]+
+        echoFilter[7]
+      );
+
+      ImGui::PushStyleColor(ImGuiCol_Text,(filterSum<-128 || filterSum>127)?uiColors[GUI_COLOR_LOGLEVEL_WARNING]:uiColors[GUI_COLOR_TEXT]);
+      ImGui::Text("sum: %d",filterSum);
+      ImGui::PopStyleColor();
+
       if (altered) {
         e->lockSave([&]() {
           flags.set("volScaleL",127-vsL);