Package Includes: (4) Beyerdynamic DT-990-PRO-250 Open Back Studio Reference Monitor Headphones(1) Rockville RHPA4 4 Channel Professional Headphone Amplifier Stereo or Mono Amp Description: The DT 990 PRO is an open dynamic headphone for studio applications. Due to a weight reduction of the diaphragm an excellent sound reproduction quality is achieved. Its rugged design with a spring steel headband ensures a secure fit and withstands all demands. Soft headband and ear cushioning systems ensure a high comfort over long periods of time. Features: DT 990 PRO Professional Open Back Dynamic Monitoring Headphones Open diffuse-field studio headphone Professional version of the many times awarded “DT 990” Extremely lightweight diaphragm for superb impulse performance Excellent sound reproduction Comfortable fit due to rugged adjustable soft padded headband construction Robust easy serviceable construction as all parts are replaceable Single-sided cable Velour circumaural ear pads Transmission type : Wired Headphone design (operating principle) : Open Headphone impedance : 250 ohms Headphone frequency response : 5 - 35.000 Hz Nominal sound pressure : 96 dB Construction : Circumaural (around the ear) Cable & plug : Coiled connecting cable with mini-jack plug (3.5 mm) & ¼“ adapter (6.35 mm) Net weight without packaging : 380 g Click Here To View The User Manual (Link Opens In A New Window) Click Here To View The Specification Sheet (Link Opens In A New Window) Features of RHPA4: Rockville RHPA4 4-Channel Professional Headphone Amplifier Inputs: ¼” and 3.5 mm input Stereo or Mono switch We include (4) ¼” TRS and (4) 3.5 mm headphone outputs run in parallel which means you can actually run 8 headphones (2 per channel) 4 Outputs each output has individual volume controls Thick metal shell casing High quality potentiometer knobs for each channel Power On” LED. DC 5V USB power supply has low power consumption BUS powered means you can get power to the unit from a power bank or through the USB on a computer or laptop Rubber feet Specifications: Input Impedance: 22K ohm Max. Input Level: +22dB Output Impedance: Min. 16Ohm Max. Gain: 20dB/Channel S/N Ratio: >98dB Frequency Response: 20 - 20 kHz S/N Ratio: > 90dB (ref 0dBu) THD: =1000mA via USB Power Adaptor Dimensions: 4.6” x 3” x 2.36” Weight: 0.85 Lbs 0dBu = 0.775Vrms Includes: Headphone amplifier USB charging cable with charging brick Owners-manual Warranty card Applications: Studio recording