Blackstar POLAR 2 Audio InterfaceFeel and response of a real guitar amp The only audio interface in the market with a FET input stage and Enhance feature that mimics the behaviour, characteristics, and electronics normally found on the input stage of a valve guitar amplifier. Plugging a guitar directly into a normal audio interface produces an anaemic signal with peaky transients, which makes playing through amp plugins sound like a plugin, not an amp. With the flick of a switch,