In my experience Humming noise comes from two main but not exclusive sources, 1. RF interference (Radio Frequency Interference) - or - 2. A bad or weak ground.
However in your case you're dealing with phono outputs and there can be some impedance matching issues involved. Check your amp input for an alternative phono setting. If that doesn't pan out, you could directly ground the phono to the amp being used. If that solves the problem then you've answered your question.
Hope I helped.
Andrew
Synesthesia Studios
However in your case you're dealing with phono outputs and there can be some impedance matching issues involved. Check your amp input for an alternative phono setting. If that doesn't pan out, you could directly ground the phono to the amp being used. If that solves the problem then you've answered your question.
Hope I helped.
Andrew
Synesthesia Studios