Expand your headphone monitoring capabilities with the addition of this 4-channel Headphone Amplifier from Monoprice!This amplifier features four 1/4 (6.35mm) amplified headphone outputs, each with its own independent volume control. It features an extremely clean amplifier circuit, which produces a signal-to-noise ratio greater than 98dB. It accepts line-level audio input over the stereo RCA jacks on the back or headphone level through the optional 1/4 TRS jack. A switch on the back allows you to choose a mono or stereo output. The amplifier is powered by the included 12 VDC/500mA AC adapter.Specifications:* Inputs: 2x RCA and 1x 1/4 (6.35mm) TRS* Input Impedance: 100 Kilohms (unbalanced)* Outputs: 4x 1/4 (6.35mm) TRS* Output Impedance: minimum 10 ohms per channel* Maximum Output Level: +22dB* Maximum Gain: 20dB per channel* Signal to Noise Ratio: > 98dB*** 30-day easy returns. No restocking fee. Free lifetime technical support. 1 year warranty. ***