Hi CJS
Indeed when the Luxe is very low on battery (close to the ESP32 not be able to boot) you might hear some hiss noise. In “normal” commercial bluetooth speakers the device turns off before you can hear this kind of audible instabilities, it could be also done in our software to avoid this in the future. I’m not sure how you measured your 3.8v as this threshold should be more around 3v.
Regarding your question, the power supply is not working exactly as you described, as the codec have a separate supply than the ESP32, and another one for the serial IC, and there is also a voltage booster for the audio amplifiers and all power supplies.
Otherwise I’m looking at the battery leakage in standby mode since this morning, and I’m not done yet. As I’m running some deep cylcle of charge/discharge it takes longer that I first expected to get a conclusion. I will keep you posted here.
Regarding stock, Europe is out of stock, a few units will be availbale in the UK this week. Still waiting for the big batch to arrive next week, enough to be in stock for a while.
EDIT: some Luxe will be available next week here in Germany https://www.berrybase.de/search?sSearch=raspiaudio
Cheers