Audio humming noise from power supply

Hello all!

I just purchased a used Virus TI synth off of Ebay. Every time I plug it into thw wall power socket, I hear a humming noise on my monitor speakers. It is very distracting. The synth can be turned off and still this happens. I do not think this is normal. This did not happen with my original synth plugged in the same way. What is causing the power supply to introduce humming into the speakers? Is the power supply defective or going bad? What in the power supply needs to be replaced?

EDIT: Has anyone had problems with the TI power supply in this way? What did you do to solve the problem?

Thank you!

Bob Graham

When I plug in headphones, there is no more hiss sound. I have plugged it into the headphone jack, and the L and R of the output where I plugged the monitors in. Can the noise be due to EMI from the powrr supply? Or will an isolation transformer or DI box do the trick?

Thanks!

Bob Graham