So I just wanted to share my setup which is a Raspberry PI 3 with Allo Digione HAT connected via SPDIF to a pair of Nubert NuPro A-700 active speakers which have a 1A USB 2.0 port on the back.
In my pursuit of keeping ground noise low and not create any ground loops (although the speakers USB ports are galvanically isolated anyways) I figured it would be neat if I could power my PI directly from this port. However the 1A are too low of a peak current for the PI. Now I found this product: Mission USB Power Cable for Fire TV Stick | Mission Accessories which is 21 EUR on amazon.
The direct amazon.de Link is https://www.amazon.de/gp/product/B078KSHVCS/
amazon.com Link is https://www.amazon.com/dp/B078KSHVCS/
It is basically a 2000 mAh Li-ion battery buffer meant for an Amazon FireTV stick. But it can power anything with a Micro USB power port. And sure enough it does power my PI 3 no problem. It will trickle charge the battery from the 1A USB 2.0 (or even a 500mA USB 1.0) port and can buffer any peaks the PI produces.
Given that the Pi 3 only consumes around 470 mA and even the Pi 4 only around 680 mA with the DigiOne HAT attached playing music, this battery buffer should work fine for both (the Pi 4 with a micro USB to USB-C adapter). Both PIs were running Ropieee with Wifi disabled and no external display.
I found this product extremely handy and figured I’d share with all of you.