I have a raspberry pi 4 with hifiberry amp 2 running volumio.
When connected to these speakers: https://www.definitivetechnology.com/products/aw6500 when volume is turned past ~50% sound starts to cut out and becomes non responsive.
When connected to these speakers it seems to work fine with higher volumes:
https://www.polkaudio.com/en-us/product/outdoor-speakers/atrium5
The power supply output is 24v / 1.8A https://images-na.ssl-images-amazon.com/images/I/61ddkRVJhaL._AC_SY355_.jpg
Your power supply isn't powerful enough. 1.8A are way too low. This is our recommenden power supply for the Amp2:
https://www.hifiberry.com/shop/accessories/power-hifiberry-80/
Would this power supply work?
24V with 2 options:
HiFiBerry US store is out of stock on their power supply: https://hifiberry.us/product/meanwell-18v-ac-adapter/
We do not recommend 24V, but 12-20V. I won't recommend 3rd party power supplies that haven't been tested by us.
if you don't want to get the HiFiBerry power supply from our shop, have a look for the Meanwell GS60A18-P1J or GST60A18-p1J that should be available from many dealers.
Other power supplies might work just as well if they provide at least stable 3.5A.
OK thanks - I have ordered the Meanwell GST60A18-P1J - will report back after I receive it!