Yoommo

Headphone Splitter, Syncwire Nylon-Braided [0.75FT/23CM] Stereo Audio Jack Splitter Cable - 3.5mm Male to 2X 3.5mm Female Aux Extension Cord for Apple, Samsung, Smartphones, Media Players - Black

AudioQuest - DragonFly Red USB DAC/Headphone Amplifier

FiiO A3 Portable Headphone Amplifier (Black)

FiiO Q5 Bluetooth aptX and DSD-Capable DAC Amplifier for iPhone, iPod, iPad & Computers with Coaxial/Optical/USB/Line/Bluetooth input

FiiO Q1 Portable USB DAC Amplifier

Headphone Audio Splitter Cable, POSUGEAR 3.5mm Male to 3.5mm Dual Female Stereo Aux Headset Y Splitter Jack Nylon Braided Cable Gold Plated Earphone Plug for Phones, Speakers, PCs, MP3 Players and Mor

FiiO E10K USB DAC and Headphone Amplifier (Titanium)

OPPO HA-2SE Portable Headphone Amplifier & DAC

BoomCloud 360 BoomStick In-Line Wired Headphone Audio Enchancer Amp and Signal Processor - Black

CHORD Electronics Mojo, ultimate DAC/Headphone Amplifier, USB, Coaxial, and Optical, Black