diff --git a/README.md b/README.md
index 4736da0..64c9d25 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,8 @@ in the source folder) stays on the Apache 2.0 license to able to collaborate bet
 Changelog
 ---------
 #### Version 0.9.2
+* Added operator mute switch
+* Added Tune (MASTER TUNE ADJ) knob
 * Single click program select
 * Fix sysex issue with wrong machine ID
 
diff --git a/Source/EngineMkI.cpp b/Source/EngineMkI.cpp
index 351e8d3..b24345e 100644
--- a/Source/EngineMkI.cpp
+++ b/Source/EngineMkI.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 Pascal Gauthier.
+ * Copyright (C) 2015-2016 Pascal Gauthier.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -245,6 +245,7 @@ void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm,
         param.phase += param.freq << LG_N;
     }
 }
+ 
 
 const FmAlgorithm EngineMkI::algo2[32] = {
     { { 0xc1, 0x11, 0x11, 0x14, 0x01, 0x14 } }, // 1
@@ -307,7 +308,7 @@ void EngineMkI::compute_fb3(int32_t *output, FmOpParams *parms, int32_t gain01,
     for (int i = 0; i < N; i++) {
         // op 0
         gain[0] += dgain[0];
-        int32_t scaled_fb = (y0 + y) >> (fb_shift + 6);     // tsk tsk tsk: this needs some tuning
+        int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);     // tsk tsk tsk: this needs some tuning
         y0 = y;
         y = Sin::lookup(phase[0] + scaled_fb);
         y = ((int64_t)y * (int64_t)gain[0]) >> 24;
@@ -352,7 +353,7 @@ void EngineMkI::compute_fb2(int32_t *output, FmOpParams *parms, int32_t gain01,
     for (int i = 0; i < N; i++) {
         // op 0
         gain[0] += dgain[0];
-        int32_t scaled_fb = (y0 + y) >> (fb_shift + 2); // tsk tsk tsk: this needs some tuning
+        int32_t scaled_fb = (y0 + y) >> (fb_shift + 1); 
         y0 = y;
         y = Sin::lookup(phase[0] + scaled_fb);
         y = ((int64_t)y * (int64_t)gain[0]) >> 24;
@@ -371,7 +372,8 @@ void EngineMkI::compute_fb2(int32_t *output, FmOpParams *parms, int32_t gain01,
 
 /*
 void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm, int32_t *fb_buf, int feedback_shift) {
-    const int kLevelThresh = 507;
+    const uint16_t ENV_MAX = 1<<ENV_BITDEPTH;
+    const int kLevelThresh = ENV_MAX-100;
     const FmAlgorithm alg = algo2[algorithm];
     bool has_contents[3] = { true, false, false };
     
@@ -382,11 +384,11 @@ void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm, int32
         int inbus = (flags >> 4) & 3;
         int outbus = flags & 3;
         int32_t *outptr = (outbus == 0) ? output : buf_[outbus - 1].get();
-        int32_t gain1 = param.gain_out == 0 ? 511 : param.gain_out;
-        int32_t gain2 = 512-(param.level_in >> 19);
+        int32_t gain1 = param.gain_out == 0 ? (ENV_MAX-1) : param.gain_out;
+        int32_t gain2 = ENV_MAX-(param.level_in >> (28-ENV_BITDEPTH));
         param.gain_out = gain2;
         
-        if (gain1 >= kLevelThresh || gain2 >= kLevelThresh) {
+        if (gain1 <= kLevelThresh || gain2 <= kLevelThresh) {
             
             if (!has_contents[outbus]) {
                 add = false;
@@ -433,5 +435,5 @@ void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm, int32
         }
         param.phase += param.freq << LG_N;
     }
-}
-*/
+}*/
+
diff --git a/Source/PluginData.h b/Source/PluginData.h
index 24d5ee0..22cc6f2 100644
--- a/Source/PluginData.h
+++ b/Source/PluginData.h
@@ -1,6 +1,6 @@
 /**
  *
- * Copyright (c) 2014-2015 Pascal Gauthier.
+ * Copyright (c) 2014-2016 Pascal Gauthier.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -30,7 +30,7 @@
 uint8_t sysexChecksum(const uint8_t *sysex, int size);
 void exportSysexPgm(uint8_t *dest, uint8_t *src);
 
-#define SYSEX_HEADER { 0xF0, 0x43, 0x00, 0x09, 0x20, 0x00 }
+#define SYSEX_HEADER        { 0xF0, 0x43, 0x00, 0x09, 0x20, 0x00 }
 #define SYSEX_SIZE 4104
 
 class Cartridge {
@@ -99,6 +99,7 @@ public:
     }
     
     int load(const uint8_t *stream, int size) {
+        const uint8 voiceHeaderBroken[] = { 0xF0, 0x43, 0x00, 0x00, 0x20, 0x00 };
         uint8 voiceHeader[] = SYSEX_HEADER;
         uint8 tmp[65535];
         uint8 *pos = tmp;
@@ -115,11 +116,13 @@ public:
                 if ( status != 0 )
                     return status;
                 memcpy(voiceData, pos+6, 4096);
+                TRACE("SYSEX Header not found, loading random data");
                 return 2;
             }
             
             pos[3] = 0;
-            if ( memcmp(pos, voiceHeader, 6) == 0 ) {
+            if ( memcmp(pos, voiceHeader, 6) == 0 || memcmp(pos, voiceHeaderBroken, 6) == 0) {
+                TRACE("SYSEX voice header found at %d", pos);
                 memcpy(voiceData, pos, SYSEX_SIZE);
                 if ( sysexChecksum(voiceData + 6, 4096) == pos[4102] )
                     status = 0;
diff --git a/Source/PluginEditor.cpp b/Source/PluginEditor.cpp
index 2e8a09a..bf18a47 100644
--- a/Source/PluginEditor.cpp
+++ b/Source/PluginEditor.cpp
@@ -115,13 +115,23 @@ void DexedAudioProcessorEditor::cartShow() {
 void DexedAudioProcessorEditor::loadCart(File file) {
     Cartridge cart;
 
-    if ( cart.load(file) < 0 ) {
+    int rc = cart.load(file);
+    
+    if ( rc < 0 ) {
         AlertWindow::showMessageBoxAsync (AlertWindow::WarningIcon,
                                           "Error",
                                           "Unable to open: " + file.getFullPathName());
         return;
     }
     
+    if ( rc != 0 ) {
+        rc = AlertWindow::showOkCancelBox(AlertWindow::QuestionIcon, "Unable to find DX7 sysex cartridge in file",
+                                          "This sysex file is not for the DX7 or it is corrupted. "
+                                          "Do you still want to load this file as random data ?");
+        if ( rc == 0 )
+            return;
+    }
+    
     processor->loadCartridge(cart);
     rebuildProgramCombobox();
     processor->setCurrentProgram(0);