Little Dot MK IV mk 4 SE Headphone Tube Amplifier Pre-Amplifier Little Dot MK IV is our flagship headphone amplifier/pre-amplifier in the Little Dot MK-series Little Dot MK IV can drive them easily with effortless dynamics (45Vp-p!) , subterranean bass, cavernous soundstage, and precise 3-D imaging Little Dot MK IV also adds in user-tweaking options such as two gain switches to delivery maximum compatibility with all your headphones, regardless of impedance or sensitivity