Strange PSU

I have a 24v switching psu that for some reason when hooked up to an amp makes the sound like a distorted mess like a wireless connection dropping in and out at the same time. It reads that it outputting 24v ; when i pull the plug out the music sounds normal for a couple of seconds before the power dissipates.

It did work properly for a while, and i have tested the amp with another psu and its fine so definitely the psu.

Any ideas would be appreciated...

Thanks
MRO Supply