Amazon.com: Pyle 4-Channel Portable Stereo Headphone Amplifier - Professional Multi-Channel Mini Earphone Splitter Amp w/4 ¼” Balanced TRS Headphones Output Jack and 1/4' TRS Audio Input For Sound Mixer - PHA40 :
Amazon.com: Pyle 4-Channel Portable Stereo Headphone Amplifier - Professional Multi-Channel Mini Earphone Splitter Amp w/4 ¼” Balanced TRS Headphones Output Jack and 1/4' TRS Audio Input For Sound Mixer - PHA40 :
Zoom ZHA-4 Handy Headphone Amplifier ZHA-4 B&H Photo Video
Amazon.com: Fifine Headphone Amplifier 4 Channels Metal Stereo Audio Amplifier,Mini Earphone Splitter with Power Adapter-4x Quarter Inch Balanced TRS Headphones Output and TRS Audio Input for Sound Mixer-N6 : Electronics
Amazon.com: Behringer MICROAMP HA400 Ultra-Compact 4 Channel Stereo Headphone Amplifier,Silver, 4.08 x 2.25 x 1.83 inches : Electronics