I am running a Naim amp which is fairly sensitive to interference compared to some brands. With the amp at 1/4 volume, I can hear a quiet but fairly noticeable hum when the HifiBerry DAC+ Pro is switched on.
The cause is almost certainly the HifiBerry power adaptor, because if I power the DAC+ from my Laptop or a cheap powerbank, it runs fine but the noise is almost entirely gone. I've tried switching sockets or power boards but anything which runs from the mains has similar levels of noise.
Any suggestions how I can improve this? I gather that a linear power supply would be ideal but these are quite expensive. Since a cheap powerbank solves the noise, I am hoping there would be a similarly cheap solution using mains power.