You probably have a lot of devices in your home that need to connect to speakers. Your TV, your stereo, your computer, and many other gadgets require speakers, or at least benefit from them. But you obviously don’t want to buy separate speakers for every individual unit. If your speakers or stereo receiver don’t have enough inputs, you could follow Redditor liamOSM’s lead and build a simple analog stereo mixer.
liamOSM has a pair of nice bookshelf speakers on his desk that are fed by a Lepy 2020 amplifier. That’s a compact amplifier that just has a single 3.5mm audio input. But liamOSM wanted to be able to connect both his Amazon Echo and his computer to the speakers. A really low-tech solution would be to use a Y-splitter cable, but then the relative volumes of the Amazon Echo and computer couldn’t be controlled.
The solution liamOSM came up with is a basic analog stereo mixer. That was made using just four resistors and two dual-ganged potentiometers. The inputs from each device are fed through the potentiometers to an output that goes to the amplifier. All liamOSM has to do is turn the potentiometers to adjust the relative volume of the corresponding input. Those were soldered onto a homemade PCB, and then placed inside a small 3D-printed enclosure. Now liamOSM has two inputs for his amplifier that can be used simultaneously.