diff --git a/MicroMDAEPiano.ino b/MicroMDAEPiano.ino
index 17957a5..c454b97 100644
--- a/MicroMDAEPiano.ino
+++ b/MicroMDAEPiano.ino
@@ -147,6 +147,7 @@ config_t configuration = {
   ENC_MIDI_CHANNEL_DEFAULT,             // midi_channel
   ENC_MIDI_SOFT_THRU_DEFAULT,           // midi_soft_thru
   ENC_MAX_POLY_DEFAULT,                 // max_poly
+  ENC_MONO_DEFAULT,                     // mono
   ENC_MASTER_PAN_DEFAULT                // pan
 };
 
@@ -245,11 +246,6 @@ void setup()
   modulator.phase(0);
   modulator.amplitude(1.0);
   modulator.offset(0.0);
-#ifdef MOD_STEREO
-  inverter.gain(-1.0); // change phase for second modulated delay (faked stereo mode)
-#else
-  inverter.gain(1.0);
-#endif
   modchorus_r.offset(15.0);
   modchorus_l.offset(15.0);
   // Butterworth filter, 12 db/octave
@@ -277,6 +273,17 @@ void setup()
   mixer_r.gain(VOL_CHORUS, 0.2);
   mixer_l.gain(VOL_CHORUS, 0.2);
 
+  // Stereo/Mono initial setup
+  if (configuration.mono == false)
+  {
+    inverter.gain(-1.0); // change phase for second modulated delay (faked stereo mode)
+  }
+  else
+  {
+    inverter.gain(1.0);
+    configuration.pan = ENC_MASTER_PAN_DEFAULT;
+  }
+
   // set master volume
   set_master_volume(master_volume);
 
diff --git a/UI.hpp b/UI.hpp
index a182ada..7f56123 100644
--- a/UI.hpp
+++ b/UI.hpp
@@ -28,16 +28,16 @@
   const uint8_t MAX_VARIABLES = 5; ///< @note Default: 5
 
   /// Configures the number of available functions per line.
-  const uint8_t MAX_FUNCTIONS = 42; ///< @note Default: 8
+  const uint8_t MAX_FUNCTIONS = 43; ///< @note Default: 8
 
   /// Configures the number of available lines per screen.
-  const uint8_t MAX_LINES = 20; ///< @note Default: 12
+  const uint8_t MAX_LINES = 22; ///< @note Default: 12
 
   /// Configures the number of available screens per menu.
   const uint8_t MAX_SCREENS = 2; ///< @note Default: 14
 
   /// Configures the number of available menus per menus system.
-  const uint8_t MAX_MENUS = 45; ///< @note Default: 8
+  const uint8_t MAX_MENUS = 46; ///< @note Default: 8
 
 */
 
@@ -56,7 +56,7 @@ int32_t encoder_value[NUM_ENCODER];
 Bounce but[NUM_ENCODER] = {Bounce(BUT_L_PIN, BUT_DEBOUNCE_MS), Bounce(BUT_R_PIN, BUT_DEBOUNCE_MS)};
 elapsedMillis back_to_main;
 
-#define NUM_MENUS 45
+#define NUM_MENUS 46
 
 #define MAIN 0
 /*************************************/
@@ -104,10 +104,11 @@ elapsedMillis back_to_main;
 #define MIDI_CHANNEL 39
 #define MIDI_SOFT_THRU 40
 #define MAX_POLY 41
+#define MONO 42
 /*************************************/
-#define STORE_QUESTION 42
+#define STORE_QUESTION 43
 /*************************************/
-#define MASTER_VOLUME 43
+#define MASTER_VOLUME 44
 /*************************************/
 
 int8_t menu_position[NUM_MENUS];
@@ -132,6 +133,7 @@ extern AudioMixer4 mixer_r;
 extern AudioMixer4 mixer_l;
 extern AudioAmplifier volume_r;
 extern AudioAmplifier volume_l;
+extern AudioAmplifier inverter;
 extern mdaEPiano* ep;
 extern config_t configuration;
 extern uint8_t sound;
@@ -285,6 +287,17 @@ char* get_midi_soft_thru_value_text(void)
   return (midi_soft_thru_value_text1);
 }
 
+char mono_value_text1[] = "      ";
+char* get_mono_value_text(void)
+{
+  if (configuration.mono == 0)
+    sprintf(mono_value_text1, "Stereo");
+  else
+    sprintf(mono_value_text1, "Mono  ");
+
+  return (mono_value_text1);
+}
+
 char yes_no_value_text1[] = "   ";
 char* get_yes_no_value_text(void)
 {
@@ -727,15 +740,17 @@ LiquidMenu save_sound_menu(lcd);
 /******************************************
    SYSTEM MENU
  ******************************************/
-#define NUM_SYSTEM_MENUS 4
+#define NUM_SYSTEM_MENUS 5
 const char system_text1[] PROGMEM = "Loudness";
 const char system_text2[] PROGMEM = "MIDI Channel";
 const char system_text3[] PROGMEM = "MIDI Soft-Thru";
 const char system_text4[] PROGMEM = "Max. Polyphony";
+const char system_text5[] PROGMEM = "Mono/Stereo";
 LiquidLine system_line1(1, 0, system_text1);
 LiquidLine system_line2(1, 1, system_text2);
 LiquidLine system_line3(1, 1, system_text3);
 LiquidLine system_line4(1, 1, system_text4);
+LiquidLine system_line5(1, 1, system_text5);
 LiquidScreen system_screen;
 LiquidMenu system_menu(lcd);
 
@@ -779,6 +794,16 @@ LiquidLine max_poly_line2(1, 1, configuration.max_poly);
 LiquidScreen max_poly_screen;
 LiquidMenu max_poly_menu(lcd);
 
+/******************************************
+   MONO/STEREO MENU
+ ******************************************/
+#define NUM_MONO_MENUS 1
+const char mono_text1[] PROGMEM = "Mono/Stereo";
+LiquidLine mono_line1(1, 0, mono_text1);
+LiquidLine mono_line2(1, 1, get_mono_value_text);
+LiquidScreen mono_screen;
+LiquidMenu mono_menu(lcd);
+
 /******************************************
    INFO MENU
  ******************************************/
@@ -1349,11 +1374,23 @@ void callback_max_poly_function(void)
 #endif
   menu_system.change_menu(max_poly_menu);
   menu_position[SYSTEM] = encoder_value[RIGHT_ENCODER];
-  encoder_value[RIGHT_ENCODER] = configuration. max_poly;
+  encoder_value[RIGHT_ENCODER] = configuration.max_poly;
   enc[RIGHT_ENCODER].write(configuration.max_poly, ENC_MAX_POLY_MIN, ENC_MAX_POLY_MAX);
   menu_system.update();
 }
 
+void callback_mono_function(void)
+{
+#ifdef SHOW_DEBUG
+  Serial.println(F("callback_mono_function"));
+#endif
+  menu_system.change_menu(mono_menu);
+  menu_position[SYSTEM] = encoder_value[RIGHT_ENCODER];
+  encoder_value[RIGHT_ENCODER] = configuration.mono;
+  enc[RIGHT_ENCODER].write(configuration.mono, ENC_MONO_MIN, ENC_MONO_MAX);
+  menu_system.update();
+}
+
 /******************************************
    INFO MENU CALLBACKS
  ******************************************/
@@ -1757,6 +1794,7 @@ void init_menus(void)
   system_screen.add_line(system_line2);
   system_screen.add_line(system_line3);
   system_screen.add_line(system_line4);
+  system_screen.add_line(system_line5);
   system_screen.set_displayLineCount(2);
   system_menu.add_screen(system_screen);
 
@@ -1764,6 +1802,7 @@ void init_menus(void)
   system_line2.attach_function(MIDI_CHANNEL, callback_midi_channel_function);
   system_line3.attach_function(MIDI_SOFT_THRU, callback_midi_soft_thru_function);
   system_line4.attach_function(MAX_POLY, callback_max_poly_function);
+  system_line5.attach_function(MONO, callback_mono_function);
 
   // setup loudness
   loudness_screen.add_line(loudness_line1);
@@ -1789,6 +1828,12 @@ void init_menus(void)
   max_poly_screen.set_displayLineCount(2);
   max_poly_menu.add_screen(max_poly_screen);
 
+  // setup mono
+  mono_screen.add_line(mono_line1);
+  mono_screen.add_line(mono_line2);
+  mono_screen.set_displayLineCount(2);
+  mono_menu.add_screen(mono_screen);
+
   // setup info menu
   info_screen.add_line(info_line1);
   info_screen.add_line(info_line2);
@@ -1845,6 +1890,7 @@ void init_menus(void)
   menu_system.add_menu(midi_channel_menu);
   menu_system.add_menu(midi_soft_thru_menu);
   menu_system.add_menu(max_poly_menu);
+  menu_system.add_menu(mono_menu);
   menu_system.add_menu(info_menu);
   menu_system.add_menu(master_volume_menu);
 
@@ -2359,6 +2405,24 @@ void set_max_poly(uint8_t value)
   ep->reset_voices();
 }
 
+void set_mono(uint8_t mode)
+{
+#ifdef SHOW_DEBUG
+  Serial.print(F("Set MONO "));
+  Serial.println(mode);
+#endif
+  if (mode == 0)
+  {
+    set_stereo(configuration.stereo);
+    inverter.gain(-1.0); // change phase for second modulated delay (faked stereo mode)
+  }
+  else
+  {
+    set_stereo(ENC_STEREO_MIN);
+    inverter.gain(1.0);
+  }
+}
+
 void set_complete_configuration(void)
 {
   set_decay(configuration.decay);
@@ -2395,6 +2459,7 @@ void set_complete_configuration(void)
   set_midi_channel(configuration.midi_channel);
   set_midi_soft_thru(configuration.midi_soft_thru);
   set_max_poly(configuration.max_poly);
+  set_mono(configuration.mono);
 }
 
 //********************************************************************************************+
@@ -2765,6 +2830,15 @@ void handle_ui(void)
             menu_system.update();
           }
         }
+        else if (menu_system.get_currentScreen() == &mono_screen)
+        {
+          if (encoder_tmp != encoder_value[RIGHT_ENCODER])
+          {
+            // value up/down
+            set_mono(encoder_tmp);
+            menu_system.update();
+          }
+        }
         else
         {
           // Move menu focus
@@ -3199,6 +3273,13 @@ void handle_ui(void)
 #endif
             goto_system_menu(MAX_POLY);
           }
+          else if (menu_system.get_currentScreen() == &mono_screen) // mono menu
+          {
+#ifdef SHOW_DEBUG
+            Serial.println(F("from mono to system"));
+#endif
+            goto_system_menu(MONO);
+          }
           else if (menu_system.get_currentScreen() == &info_screen) // info menu
           {
 #ifdef SHOW_DEBUG
diff --git a/config.h b/config.h
index 0e28e9d..49850dd 100644
--- a/config.h
+++ b/config.h
@@ -31,7 +31,7 @@
 // 128 to 64 in <ARDUINO-IDE-DIR>/cores/teensy3/AudioStream.h
 
 // arecord -f cd -Dhw:1,0 /tmp/bla.wav
-// aplaymidi -p 20:0 test.mid 
+// aplaymidi -p 20:0 test.mid
 
 //*************************************************************************************************
 //* DEVICE SETTINGS
@@ -60,7 +60,7 @@
 // CHORUS parameters
 #define CHORUS_DELAY_LENGTH_SAMPLES (16*AUDIO_BLOCK_SAMPLES) // one AUDIO_BLOCK_SAMPLES = 2.902ms
 #define WAVEFORM_MOD WAVEFORM_TRIANGLE // WAVEFORM_SINE WAVEFORM_TRIANGLE WAVEFORM_SAWTOOTH WAVEFORM_SAWTOOTH_REVERSE
-//#define MOD_STEREO 1
+
 //*************************************************************************************************
 //* DEBUG OUTPUT SETTINGS
 //*************************************************************************************************
@@ -99,7 +99,7 @@
   30: 1.22 Volts p-p
   31: 1.16 Volts p-p
 */
-#define SGTL5000_LINEOUT_LEVEL 26
+#define SGTL5000_LINEOUT_LEVEL 25
 //#define SDCARD_CS_PIN    10
 //#define SDCARD_MOSI_PIN  7
 //#define SDCARD_SCK_PIN   14
@@ -286,6 +286,10 @@
 #define ENC_MAX_POLY_MAX NVOICES
 #define ENC_MAX_POLY_DEFAULT NVOICES
 //
+#define ENC_MONO_MIN 0 // stereo
+#define ENC_MONO_MAX 1 // mono
+#define ENC_MONO_DEFAULT 1
+//
 #define ENC_MASTER_VOLUME_MIN 0
 #define ENC_MASTER_VOLUME_MAX 99
 #define ENC_MASTER_VOLUME_DEFAULT 80
@@ -351,6 +355,7 @@ struct config_t {
   uint8_t midi_channel;
   bool midi_soft_thru;
   uint8_t max_poly;
+  uint8_t mono;
   int8_t pan;
 };
 
diff --git a/mdaEPiano.cpp b/mdaEPiano.cpp
index 45af0fe..f23886a 100644
--- a/mdaEPiano.cpp
+++ b/mdaEPiano.cpp
@@ -257,7 +257,7 @@ void mdaEPiano::setOverdrive(float value)
 void mdaEPiano::setLoudness(float value)
 {
   //volume = value * 0.32258; // 0.00002 * 127^2
-  volume = value * 0.18f;
+  volume = value * 0.17f;
 }
 
 void mdaEPiano::setParameter(int32_t index, float value)