I was using it with headphones, but it's malfunctioning, making a high-pitched, howling sound, possibly due to a contact issue. There are times when it doesn't happen. Other than that, there are no problems with Bluetooth, smartphone linking, or the sound library. I'm selling it at a low price, so no claims and no returns, please! I will answer your questions as quickly as possible. Here's the product description: The NUX Mighty Plug Pro is a plug-in guitar effector with a volume control button. - Brand: NUX - Model Name: Mighty Plug Pro - Function: Guitar effector - Connection Type: Plug-in - Control Buttons: Volume control button