I am using a Re-audio SA 90.4 800W 4-channel class D audio amplifier (https://www.amazon.com/REAudio-SA90-4-4-Channel-Digital-Amplifier/dp/B00RE9EO7K) for some underwater piezoacoustics experiment. The setup is as follows:
- The piezo cylinder is mounted in a watertight shell with +ve and -ve cables connected to one of the amplifier output channels. Impedance varies from 50-500 ohm (depending on frequency as checked with a impedance analyzer)
- The amp is powered by a labbench 80W powersupply (yes I know it's not enough but I ensured the gain was limited using gain controls of the amplifier)
- The amp is fed by a 96 KHz DAC via RCA cable (left and right cable). It has two sets of RCA ports.
During the experiment, after ~10 minutes, one of the RCA ports gave out. I suspect it's the RCA port because when I connected the inputs to the other RCA port, the setup started working as normal, until that port gave out after 10 minutes. Now the amplifier turns on but there is no output. The piezo cylinder is fine (tested with another smaller pre-amp and impedance analyzer). Note that the amp is rated for 4-8 ohms at the output but no rating is specified for the input RCA channels.
I would appreciate if someone could help me narrow down the problem. I opened the amp and did not seem to find any damaged component inside.