HeadAMP – Four Output Stereo Headphone Amp – ART Pro Audio
HPFX – Headphone Mixer/Amplifier – ART Pro Audio
Presonus HP4 Headphone AMP/Mixer – Raines Africa
Amazon.com: Riworal 4 Channels Headphone Amplifier with 1/4" and 1/8" TRS Jack Input for Dj Mixer Headphone Mixer Amps Headphone Splitter with Separate Volume Control Output for Speaker Or Monitor Headphone :
jamming - Is there a device that would be a mixer with multiple outputs to jam with headphones? - Music: Practice & Theory Stack Exchange