I have a couple of these amplifier boards:
https://www.ebay.co.uk/p/Xh-m253-Tda8954th-Core-BTL-Mode-HIFI-Class-420w-High-Power-Mono-Digital-Amp-Z4w4/21020333806
Based on this:
https://www.nxp.com/docs/en/data-sheet/TDA8954.pdf
I am trying to test them for a project and am using a raspberry pi headphone out as the input. I am using a 19VDC laptop charger instead of the 24V AC printed on the board (I am pretty sure the ebay ad is wrong), as there is a bridge rectifier straight after the power terminals, so this should give around 18V to the chip (I think). There is a blue power LED which is lit fine.
The headphone out works fine with headphones, and I can get the speaker working running the headphone cable straight to it, so the problem is definitely the amp.
The resistance across the input terminals of the amp is measuring infinite, would this cause a problem as headphones would obviously have a finite resistance.
Not getting anything from the speakers, and not measuring an AC voltage across the input terminals (not sure if I should be able to with a standard multimeter?)
What have I missed? Any help appreciated!
Thanks