The AC hum issue can be this problem.  Electricians, take note:

    In the vast majority of cases where 'dedicated lines are installed to feed audio systems, huge ground and hum issues develop.
In the USA, AC power is delivered to domestic loads as a 240 volt system, that is center tapped into two 120 volt rails that are actually out of phase relative to one another.
When 'dedicated lines' are run by the average electrician, the usual practice is to just line up a row of breakers and hook up wire to the room....BAD AND WRONG!

    What happens is that any asymmetry in the AC voltage waveform, and there IS asymmetry, is feeding the system and difference will flow as ground currents that produce hum.
There is only one fix for this....the multiple AC lines that feed a given system MUST and ALWAYS come from only ONE of the AC rails...never a mixture of the two.

    Time and time and time again, over and over, we see incorrectly wired multiple dedicated lines that cause hum and buzz issues that are rarely resolved, until the AC feed is corrected to source from a single phase of the AC system. 
    In the normal course of training for electricians, they are instructed to 'balance the loads' ..meaning that if you have 30 thousand watts of consumption over the layout of a house, lighting, outlets and such, that the goal is to spread out that 30 thousand watts so that approximately half of it is fed from one polarity and half from the other polarity. This is fine for light bulbs, small appliances and such, but when opposing phases are feeding a single audio system where ground is part of the signal and connected to all the gear, all hell breaks loose.
    Electricians are NOT educated in the fine art of what is correct for high end audio...only for balancing the lighting and small appliance loads throughout the house.
Audio gear that interfaces with no ground connection, as we see in most professional systems, and some consumer gear, VIA a real balanced differential connection interface, are usually immune to such issues, as the ground and AC neutral are NEVER used as any sort of reference point from which the audio signal is created or sensed.

    However the reality is that most consumer gear is single ended RCA jack interface and if that is the case, GROUND IS IN YOUR SIGNAL PATH!!!  ....any ground currents flowing between equipment WILL and DO add to the signal. We hear this as hum and buzz. No AC noise remover on earth can correct for this condition.  The only cure is to FIRST correct the AC feed problem... Even after this is done, hum and buzz can still exist, but the causes are different...but first things first...get the AC fixed correctly.

Jennifer Crock
JENA technologies



        ac power issues-hum Updated Jan 6th 2015 Jena Technologies LLC

left border
Welcome to AC power products page