Frequently, depending on the settings when the audio file was created, the audio files volume may be very low. Our product is designed to "expect" normal music audio done by studios at industry standard settings. If your audio files audio is much quieter than that, then it may be difficult for you to adjust the volume enough using the controller or your phone to compensate for this.This is most obvious to hear if you can play a standard "professional" music file and the volume is fine, but when you play your audio recording (without changing any settings), the volume is way to low. This means that your audio files volume is not to industry standards.But there is a fairly easy solution.There are several free tools online available to increase the volume of an audio file. We've had customers for years use CloudConvert successfully to convert most file types to other file types as well as make adjustments to the audio file. Here's a link to it: cloudconvert.com/mp3-converterWe suggest you set the bit rate to 128 kbps. Then increase or decrease the volume for you if you need to change the volume of the original file. Additionally, you can tell it to trim audio off the end of the file if you have extra audio dead space you need to get rid of.After using the tool, just save the new mp3 file to your computer and then transfer it to the controllers memory as directed in the user guide. Of course, please feel free to contact us if you need additional assistance.