Audio hum and neutral faults?

[mbrooke]

Can a grounded neutral (neutral touching a ground wire) in a branch circuit effect audio equipment? Can this cause audio equipment such as guitar amps to produce a 60hz hum/buzz or is this just a myth?

 

[fmtjfw]

Yes, the neutral will be at a voltage above "true" ground. Many audio input circuits reference ground. If you have a source that references the elevated ground (with a 60Hz component) from a neutral crossed with a grounding conductor and connects to a device that references "true" ground, then hum will be evident.

If you are careful to make all the grounds for all the sources and equipment be at the same level (one of the ideas behind isolated grounding) then hum can be reduced.

You can also use audio-transformer-based isolation that eliminates the actual connection between the source and destination grounds by coupling the signal only magnetically through the transformer.

 

[mbrooke]

Yes, the neutral will be at a voltage above "true" ground. Many audio input circuits reference ground. If you have a source that references the elevated ground (with a 60Hz component) from a neutral crossed with a grounding conductor and connects to a device that references "true" ground, then hum will be evident.

If you are careful to make all the grounds for all the sources and equipment be at the same level (one of the ideas behind isolated grounding) then hum can be reduced.

You can also use audio-transformer-based isolation that eliminates the actual connection between the source and destination grounds by coupling the signal only magnetically through the transformer.

Thanks!


So a neutral to ground bond will cause certain audio equipment to hum. Also, can the EMFs from a grounded neutral also cause this or is it just the elevated ground voltage from the grounded neutral?

 

[ghostbuster]

If there is (unbalanced) current flow on this neutral it will generate a magnetic field.This magnetic field (if strong enough) can then couple into the amplifier (tube amplifiers are generally the most susceptible.)

 

[mbrooke]

If there is (unbalanced) current flow on this neutral it will generate a magnetic field.This magnetic field (if strong enough) can then couple into the amplifier (tube amplifiers are generally the most susceptible.)

Thanks. Looks like both the EMFs and the elevated voltage to ground will cause hum. Double whammy then.


In regard to the EMF Ive also seen them make old cathode ray tube computer monitors jitter.

 

[ghostbuster]

These monitors (in the good old days) were considered to be the like the canaries you would put in the mine shafts to detect harmful gases.If the monitor screen text jittered you were being exposed to these emf's.