The Calrad 10-115A Compact headphone amplifier is ideal for any application where a line level source needs to be monitored. It is also suitable for use with portable devices whose headphone output does not provide adequate audio output levels. Stereo RCA and 3.5mm input jacks for line level source signals. Seperate output connectivity for using 1/4” or 3.5mm stereo headphones. Power is supplied by a dc power supply (Included) or a micro USB jack for portable use. Analog rotary style volume control with on\off power switch. Visible front panel red power LED.