I have a special love for small battery-powered amps! An odd thing to admit, perhaps, but they are intertwined in my DIY journey due to an extensive period of playing around with circuit bending. For those not familiar with the term, circuit bending is the manipulation of and tinkering with battery-powered noise-making toys and objects with little to no theory. Simply adding capacitance with fingers or creative short-circuiting is very much the circuit bending way. As such, you must ensure you are only connected to battery-powered amps for your physical well-being. This LM386 audio amplifier could be the perfect desk amp for your sonic experiments!
Supplied as just the PCB, this small board once populated will output up to 700mW into a 8-ohm speaker. Small 8-ohm speakers are pretty easy to find, even salvaged from a toy. It should be noted the LM386 audio amplifier circuit can drive quite large speakers, although without huge amounts of volume. There is an excellent video on the product page with this circuit built into a vintage guitar practice amp which shows what the little amp can do. Of course, being a small board, you could also mount the device inside your noise-making project for portable electronic noise-making fun.
The documentation link has a list of the common components you’ll need to source to complete this design and you’ll need to also add a 9V battery to get this up and running. The LM386 is a flexible amplifier and can be used for a lot of different projects, not just audio. Its internal schematic is a great starting place if you want to learn about amplifiers inside integrated circuits!