Purchased in 1998 at Guitar Center in New York, this Electro-Harmonix Big Muff allows for tone adjustment with its three knobs. As it's an early model, it doesn't have a red indicator light on the body. I currently don't own an amplifier, so I haven't been able to confirm its functionality. Please be aware of this. A new 9V battery is included. - Model Name: Big Muff - Brand: Electro-Harmonix - Number of Knobs: 3 - Input Jacks: 1 - Output Jacks: 1 Thank you for looking.