I installed several mods on my GBA: an IPS display, upgraded speaker and amp, lithium battery, and a FlashCart. Since the GBA was never designed to power all of this hardware, I was repeatedly advised (on Reddit and various GBA modding sites) to add a Power Cleaner.
The Power Cleaner itself is a flexible PCB carrying six additional capacitors. It is designed to “piggyback” onto the original capacitors on the GBA motherboard, and the layout makes installation extremely straightforward. Just tin the pads, tin both ends of the existing capacitors, and solder the Power Cleaner to them so the pads make solid contact. The process is quick and forgiving; just be careful not to overheat the stock capacitors or you risk lifting them.
As for the results, I cannot say with certainty how dramatic the improvement is. I still notice a faint hum or buzz from the speaker at high volume. From what I have learned since installing it, this mod is not meant to eliminate the noise entirely, only reduce it. I also did not do a before and after test since I installed all my mods at once. Still, I am confident that without the Power Cleaner the noise would be more noticeable.
I originally expected total silence, so I was tempted to rate this lower, but that was before I understood the realistic limitations. Given the circumstances, and the fact that it likely is improving stability, I think it is a worthwhile addition for anyone doing similar upgrades.
And one last note: despite jokingly being called a “guinea pig,” I genuinely loved the paper packaging. Great move, ZedLabs!