diff --git a/UI.hpp b/UI.hpp
index 66f983a..a56673c 100644
--- a/UI.hpp
+++ b/UI.hpp
@@ -232,9 +232,9 @@ void setup_ui(void) {
   lcd.setFont(u8x8_font_amstrad_cpc_extended_f);
 #endif
   lcd.setCursor(1, 0);
-  lcd.print("MicroDexed");
+  lcd.print(F("MicroDexed"));
   lcd.setCursor(0, 1);
-  lcd.print("(c)parasiTstudio");
+  lcd.print(F("(c)parasiTstudio"));
 
 #ifdef I2C_DISPLAY
   // set special chars for scrollbar
@@ -703,7 +703,7 @@ void lcdml_menu_display(void)
         }
         else {
           lcd.setCursor((_LCDML_DISP_cols - 1), n);
-          lcd.print(' ');
+          lcd.print(F(" "));
         }
       }
     }
@@ -948,7 +948,7 @@ void UI_func_chorus_frequency(uint8_t param)
 
     lcd.setCursor(0, 1);
     lcd_display_float(configuration.chorus_frequency / 10.0, 2, 1, false, true, false);
-    lcd.print(" Hz");
+    lcd.print(F(" Hz"));
 
     modulator.frequency(configuration.chorus_frequency / 10.0);
   }
@@ -995,15 +995,15 @@ void UI_func_chorus_waveform(uint8_t param)
     {
       case 0:
         modulator.begin(WAVEFORM_TRIANGLE);
-        lcd.print("[TRIANGLE]");
+        lcd.print(F("[TRIANGLE]"));
         break;
       case 1:
         modulator.begin(WAVEFORM_SINE);
-        lcd.print("[SINE    ]");
+        lcd.print(F("[SINE    ]"));
         break;
       default:
         modulator.begin(WAVEFORM_TRIANGLE);
-        lcd.print("[TRIANGLE]");
+        lcd.print(F("[TRIANGLE]"));
         break;
     }
   }
@@ -1708,9 +1708,9 @@ void UI_func_volume(uint8_t param)
   for (uint8_t i = 0; i < LCD_cols; i++)
   {
     if (i < int((LCD_cols - 2) * configuration.vol / 100.0))
-      lcd.print("*");
+      lcd.print(F("*"));
     else
-      lcd.print(" ");
+      lcd.print(F(" "));
   }
   lcd.show(1, 0, 1, "[");
   lcd.show(1, 15, 1, "]");
diff --git a/config.h b/config.h
index 12869bf..0be817d 100644
--- a/config.h
+++ b/config.h
@@ -45,12 +45,16 @@
 //* DEVICE SETTINGS
 //*************************************************************************************************
 
-// MIDI
+//*************************************************************************************************
+//* MIDI HARDWARE SETTINGS
+//*************************************************************************************************
 //#define MIDI_DEVICE_DIN Serial1
 #define MIDI_DEVICE_USB 1
 #define MIDI_DEVICE_USB_HOST 1
 
-// AUDIO
+//*************************************************************************************************
+//* AUDIO HARDWARE SETTINGS
+//*************************************************************************************************
 // If nothing is defined Teensy internal DAC is used as audio output device!
 // Left and right channel audio signal is presented on pins A21 and A22.
 #define AUDIO_DEVICE_USB
@@ -62,9 +66,8 @@
 #define PT8211_AUDIO
 
 //*************************************************************************************************
-//* MIDI SETTINGS
+//* MIDI SOFTWARE SETTINGS
 //*************************************************************************************************
-
 #define DEFAULT_MIDI_CHANNEL MIDI_CHANNEL_OMNI
 #define MIDI_MERGE_THRU 1
 #define SYSEXBANK_DEFAULT 0
@@ -83,7 +86,7 @@
 //#define USE_REVERB 1
 
 //*************************************************************************************************
-//* AUDIO SETTINGS
+//* AUDIO SOFTWARE SETTINGS
 //*************************************************************************************************
 // https://rechneronline.de/funktionsgraphen/
 #ifndef TEENSY_AUDIO_BOARD
@@ -142,7 +145,6 @@
 #endif 
 
 #define CONTROL_RATE_MS 50
-
 #define BACK_FROM_VOLUME_MS 1000
 
 //*************************************************************************************************
@@ -157,7 +159,6 @@
 //*************************************************************************************************
 //* HARDWARE SETTINGS
 //*************************************************************************************************
-
 #if defined(__IMXRT1062__) //Teensy-4.0
 #define TEENSY4
 #endif
@@ -249,9 +250,8 @@
 
 // Some optimizations
 #define USE_TEENSY_DSP 1
-#define SUM_UP_AS_INT 1
 
-/* HELPER MACROS */
+// HELPER MACROS
 #define TIME_MS2SAMPLES(x) floor(uint32_t(x) * AUDIO_SAMPLE_RATE / 1000)
 #define SAMPLES2TIME_MS(x) float(uint32_t(x) * 1000 / AUDIO_SAMPLE_RATE)
 // Modulated delay options
@@ -368,12 +368,6 @@ struct config_t {
   uint8_t engine;
 };
 
-// struct for smoothing value changes
-struct value_change_t {
-  float diff;
-  uint16_t steps;
-};
-
 inline float mapfloat(float val, float in_min, float in_max, float out_min, float out_max)
 {
   return (val - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
diff --git a/effect_stereo_mono.cpp b/effect_stereo_mono.cpp
index 6ceae55..8eb9067 100644
--- a/effect_stereo_mono.cpp
+++ b/effect_stereo_mono.cpp
@@ -45,6 +45,7 @@ void AudioEffectStereoMono::update(void)
   {
     if (block[0] && block[1])
     {
+#ifdef USE_OLD_STEREO_TO_MONO
       int16_t *bp[2] = { block[0]->data, block[1]->data };
 
       for (uint16_t i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
@@ -54,6 +55,15 @@ void AudioEffectStereoMono::update(void)
         bp[0]++;
         bp[1]++;
       }
+#else
+      // device every channel by 2 
+      arm_shift_q15(block[0]->data, -1, block[0]->data, AUDIO_BLOCK_SAMPLES);
+      arm_shift_q15(block[1]->data, -1, block[1]->data, AUDIO_BLOCK_SAMPLES);
+      // add channel 2 to channel 1
+      arm_add_q15(block[0]->data, block[1]->data, block[0]->data, AUDIO_BLOCK_SAMPLES);
+      // copy channel 1 to channel 2
+      arm_copy_q15(block[0]->data, block[1]->data, AUDIO_BLOCK_SAMPLES);
+#endif
     }
   }