Firestone Audio Cute CURVE Headphone Amp - Silver Amplifier Structure : Coupling capacitor less, Push-Pull with Class-B Headphone Impedence : 32 ohm to 600 ohm Connectivity: Line Input : 1 of RCA jack/Line Output : 1 of 6.4mm phone jack Gain Control : Low (attenuation 20dB) / High (normal) Frequency response (From 40Hz to 15kHz) : 40Hz +0.01dB, 15kHz -0.02dB