PAM 8403 with Bluetooth - First Impressions

The PAM 8403 that I ordered from Ali Express arrived yesterday. Just hooked it up with my Diamond IV for testing. What a nice surprise!

A really serious amplifier, plays loud at 72 dB at 1 metre without distortion, and good bass. No trace of class D metallica. There is that slight mid to high range emptiness, but this was swiftly corrected with a equalizer setting, and this is Bluetooth 4 after all, from my HTC explorer legacy device.

My previous 8403 burned out when I shorted out the speakers terminals I think, so must be careful. A great reference amp. Really nice.

Connected to '4 Ohm' speakers it played for a few minutes then I heard a sudden 'motoring' noise, shut off the power immediately. The noise even cut out the "Bluetooth mode" voice message when turning on and off.

Switched back to my 8 Ohm Diamond 4s and everything was fine. Overheating? Anyone encountered this?
Yes, thanks, that may explain it, because I was using a low voltage power supply - batteries - 4.5 V at most, and it did experience the problem when
driving 4 Ohm speakers.

Also, note to myself:

I have had a similar problem - I crocodile clipped the power and left in and left speaker connections maybe there was a short circuit, which is why I will be going for boards with pre-connected output pins instead of having to solder these.

The entire board gets very hot, the chip gets very hot as well. Very disappointing. No sound out of the speaker. Every instruction I see says do not connect the output grounds. Maybe I did.
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And batteries? 9V maybe? It does have a low current cut off. Maybe that's it.
My mistake, I was thinking of my LM386. Of course I am using 3 x 1.5 V. Some people use capacitors in the power supply circuit:

2023-03-01 7:51 am2023-03-01 7:51 am
Its got a 4 farad super cap on the power rail, the PAM 8403 amp that I was using previously would work for a few minutes on 4 farad cap alone, but it is still possible that a peek would be so much higher than average that it saps the power.