I have a JVC UX-D150 for ~£250 ~5 years ago https://www.amazon.co.uk/JVC-UX-D150-Wireless-Micro-Amplifier-Silver-Black/dp/B01DACR3FY which is not working.
It is as if it has no gain anymore, because you can feebly hear the source if you crank the volume up to the max.
It is good for a repair...