Amazon.com: Audio Mixer, DIY Headphone Amplifier, Mini Stereo Mixer 4 in 1 Out with Volume Adjustment, 3.5mm Sound Selector Amplifier for PC Laptop Headphone, : Home & Kitchen
DIY Mini Audio Mixer With Sound Effect - YouTube
Rakimix 5 Channel Mixer Kit – Rakit
Build an Audio Mixer - Projects
Professional Sound Mixer Circuit - Homemade - YouTube