Ground loop/hum with record player preamp to DAC+ ADC & AAmp60


I have a Pi3 with a DAC+ADC & a AAmp60 powered by a 18v 3.5A power brick. I'd like to use a turntable with this setup and have a Preamp (Pro-Ject Phono Box) that I've connected to the DAC+ RCA inputs. It technically works but there's a horrific hum that I assume is caused by a ground loop.

What's a safe and sensible approach to remove the ground loop? I'd guess I could share a ground to the Pi, or perhaps power both the Preamp and Pi+Amp with the same supply (they're both 18v)? But I'm quite hesitant when I don't really know what I'm doing so thought I'd post here first.

Any suggestions would be very welcome. Thanks!


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