Great device, just plug & play, no batteries needed, just add it between mic & I mic input to boost volume (absolute godsend with a Traktor S5 .. now mic works flawlessly). Only downside, no instructions, nothing, not even a piece of paper with a diagram.. but it?s easy to use & can be left & forgotten. Great piece of Kit, Native Instruments should bundle this with the S4 / S5, now people can finally hear the mic!,