Report KGSSHV Carbon Build Thread in Do It Yourself Posted December 22, 2019 On 12/13/2019 at 11:18 PM, mwl168 said: The hum is present with the Carbon amp OFF? Positive. I suspect ground wiring issues outside of the amp but not sure yet. On 12/14/2019 at 7:41 PM, UFN said: A toroid transformer that's audibly humming is normally either badly made, overloaded or miswired. Does it hum without load as well? Also, you do know about shorted turns on toroids, right? https://www.bicronusa.com/resources/tech-guide-toroidal-power-transformers Will test the no-load hum as well as the efficiency and the power consumption. Maybe I have a short somewhere? I can sort out the shorted turn since nothing is connected to the top metal plate.