diff --git a/abogen/conversion.py b/abogen/conversion.py
index 66386dd..ae26807 100644
--- a/abogen/conversion.py
+++ b/abogen/conversion.py
@@ -348,7 +348,11 @@ class ConversionThread(QThread):
                 # Set split_pattern to \n+ which will split on one or more newlines
                 split_pattern = r"\n+"
                 
-                loaded_voice = get_new_voice(tts, self.voice, self.use_gpu)
+                # Check if the voice is a formula and load it if necessary
+                if '*' in self.voice:
+                    loaded_voice = get_new_voice(tts, self.voice, self.use_gpu)
+                else:
+                    loaded_voice = self.voice
                 
                 for result in tts(
                     chapter_text,
diff --git a/abogen/gui.py b/abogen/gui.py
index 23b44ed..f5bfe0b 100644
--- a/abogen/gui.py
+++ b/abogen/gui.py
@@ -1049,13 +1049,17 @@ class abogen(QWidget):
                 else self.subtitle_mode
             )
             
-            voice_formula = self.voice_formula.toPlainText()
-            
+            # if voice formula is not None, use the selected voice
+            if self.mixed_voice_state:
+                formula_components = [f"{weight} * {name}" for name, weight in self.mixed_voice_state]
+                voice_formula = " + ".join(filter(None, formula_components))
+            else:
+                voice_formula = self.selected_voice
+
             self.conversion_thread = ConversionThread(
                 self.selected_file,
                 self.selected_lang,
                 speed,
-                #self.selected_voice,
                 voice_formula,
                 self.save_option,
                 self.selected_output_folder,