I decided to see how low you can get in costs for amplifiers suitable to drive a piezo buzzer sound installation. Basically you get all sort of digital amplifier ICs soldered on a small board with a basic circuit around.

This is the first one I'm testing which comes at ~2 EUR for a mono channel. The board is described as based on TDA2030. It can run off 6 to 12 V (I am using a 12V power supply), has four input pins for line signal and power, and a screw terminal for the amplified output. There is a small potentiometre that can be used to attenuate the amplification. I ended up having it turned down most of the way.

The amplified signal is fed to a single piezo buzzer using an intermediary transformer coil designed for 100V technique, in this case achieving a better match between the typical output impedance of an audio amplifier (suitable to 4 to 8 Ohms) and the higher impedance of the piezos (around 200 Ohms can be measured at DC).

With the forgiving test sound file of spoken word, the quality seems ok, if you make sure the piezo is not distorting mechanically.