Getting Rid of Transformer Hum
Magnetostriction. It’s usually another item in the home that will cause amp hum (not heard through the speakers) Most common items are: LED lights, Fan Speed controls, Some lamp dimmers, proportional temp controls on old range tops, coil heaters with thermostat fans, etc. None should be leaking DC back into the mains but they often do. |
I appreciate your response. A new halogen desk light set at 1/2 on a different circuit solved my AMP5 Hum eight years later. I also noticed an annoying pulsating hum that reminds me of a lightsaber match from Star Wars once it was connected to a power source. |
Two things, one it concerns me that you are seeing such a large drop under load. Some drop is expected. That large a drop could be indicative of a poor connection somewhere or undersized wires. DC offset on the AC line is caused by unbalanced loading on the positive and negative going sides of the AC wave. It does not happen often, but it also does not take much to cause hum. Old 2 position dimmers (popular on range hoods), 2 position motor speed controllers (some ceiling fans) may in one switch position only conduct for 1/2 a cycle. With other electronic equipment performing poorly, the conduction on one 1/2 the cycle may be lower. Result is DC offset on the AC line. iFi, Isotek, audiolab, ATL audio, etc. make these. There is not a lot in them. Couple of capacitors and some diodes. The diodes are to ensure the voltage on the capacitors never gets very large. If it does not have a safety certification (UL, TUV, ENEC, etc.), then get one in a metal box in case there is a failure. |
