I decided to try to go back to the setup of the first Writing Machine, with individually amplified channels. Only now, twelve years had passed, and it would be much easier to produce the number of desired channels. In the Rogues, I had already used quite inexpensive digital amplifier circuit boards, but now I wanted to amplify 24 channels, so the boards would have to be very cheap.
I think I ordered in total five or more models, some monophonic, some stereophonic, where the price per channel came down to around 2 to 3 EUR. I compared them in terms of the clarity of sound, amount of noise and distortion, and their overall capacity to produce a strong enough signal on the piezo discs.
I knew from the original piece, that transformer coils made for 100V amplification would help to match the high impedance of the piezos with the low impedance of the amplifiers, and indeed this worked well again. But now I would also have to get hold of many of those coils, and it turned out they are quite expensive in themselves. In the end it was more feasible to do without the coils but get a slightly stronger amplifier. The one I ended up with is the third depicted here, based on the Texas Instruments TPA3110 chip.
The circuit board design, offered basically identical by various different vendors, sports a prominent light blue heat sink, which will eventually be visible in the installation.