diff --git a/cubesatsim/cubesatsim.ino b/cubesatsim/cubesatsim.ino
index 645036ce..7607cc44 100644
--- a/cubesatsim/cubesatsim.ino
+++ b/cubesatsim/cubesatsim.ino
@@ -2021,10 +2021,11 @@ void pwm_interrupt_handler() {
 // based on code https://github.com/rgrosset/pico-pwm-audio
 //	
     pwm_clear_irq(pwm_gpio_to_slice_num(AUDIO_OUT_PIN));    
-    if (wav_position < (WAV_DATA_LENGTH<<3) - 1) { 
+//    if (wav_position < (WAV_DATA_LENGTH<<3) - 1) { 
+    if (wav_position > (buffer_size - 1)) { 
         // set pwm level 
         // allow the pwm value to repeat for 8 cycles this is >>3 
-        pwm_set_gpio_level(AUDIO_OUT_PIN, buffer[wav_position>>3]);  
+        pwm_set_gpio_level(AUDIO_OUT_PIN, buffer[wav_position]);  
         wav_position++;
     } else {
         // reset to start