I recently purchased the Stellar S300 (which I am loving) but I am having a hard time trying to get rid of the hum from my subwoofer (REL T9/i) when I put the S300 into standby. There is no hum from the sub when the S300 is powered on but as soon as I turn off the amp, there is what sounds like a ground loop hum. I’ve tried everything I can think of and everything I have been able to find online and would really appreciate some words of wisdom from anyone that has had the issue and managed to solve it. This is how it is connected and this is what I have tried:
The Rel sub is connected to the S300 via the high-level speakon connector, with the yellow and red wires going to the left and right positive terminals on the S300 and the black wire going to the ground point on the S300 (which I believe is a feature on the newer S300 units as it isn’t present on the demo unit at the shop which I purchase it from). This is the setup that produces the least amount of hum.
I have tried leaving the black wire unconnected but that makes the hum worse.
I’ve tried using a different power board thinking there may be an earthing problem.
I have tried lifting the earth on the sub only (removed the ground pin from the cable) and then lifting the earth on the amp only and then lifting both. Still it hums.
I’m at a loss as to how to fix the problem and/or whether there is an issue with the grounding on the S300. It doesn’t effect listening but it means I have to switch off the sub whenever I put the S300 into standby. Any help/guidance would be greatly appreciated.