I wanted to make music with my iPad, a small MIDI controller (AKAI MPK Mini), and a collection of old phones and tablets each running a dedicated “instrument.” I wanted the setup to be versatile and fun, but also extremely compact - small enough to fit in a laptop case.
One challenge for this was merging all the audio signals together. Since each device has its own volume control, level knobs were able to be omitted from this passive mixer. The internals are a simple array of resistors soldered in a “dead bug” floating fashion. The case is made from laser cut scrap acrylic. The mixer takes up to 8 inputs via 3.5mm TRS jacks and sends them to 2 3.5mm TRS outputs. Because it is not powered, it must be plugged into an output that has amplification. Part of the setup includes as FiiO E6 headphone amplifier. Theoretically, the setup could be used for performances with the headphones plugged into one output as a monitor and the other output plugged into the PA.
