Why hum goes away on amp....

[Gazdatronik]

When the ground pin for said amp is removed.

What in the name of electrical science is going on here?

I should add, the hum only shows its ugly face when the flourescent kitchen lights are on. Same circuit as the living room.

 

[nj pheonix]

Ground loop
You're picking up noise.
Flourescent lighting is inherently very noisy.
Maybe try LEDS.
If its possible to plug the equipment into an outlet on a different circuit it might help.
Alternately switch the lighting to a different circuit.
You could use an extension cord to test. If the plug on the gear isn't polarized, you could try flipping it in place.

 

[Gazdatronik]

Ground loop
You're picking up noise.
Flourescent lighting is inherently very noisy.
Maybe try LEDS.
If its possible to plug the equipment into an outlet on a different circuit it might help.
Alternately switch the lighting to a different circuit.
You could use an extension cord to test. If the plug on the gear isn't polarized, you could try flipping it in place.

The system is powered by two receptacles about 8 feet apart, I have moved all the devices to a single plug.

The hum has now greatly reduced, but is still there. I may attempt to move the overhead lighting to another circuit. Its a funky setup, garage electrical, kitchen and dining room light, plus the living room plugs all on one breaker. The rest of the house is more sensibly apportioned.

 

[northpaw]

That you can extinguish the hum by lifting the ground pin on the amp does make it seem as if there is a ground loop, but the fact that the hum isn't there when the lights are off makes It is unlikely to be a ground loop within your audio system itself.

Agree that florescent lights can be noisy, but since lifting the ground pin on the amp extinguishes the noise, even when the lights are on, suggests that the florescent lights are polluting the ground when they are on.

Perhaps there is something wrong in the way those lights are wired, such as tying common and ground together? Just guessing here.

 

[avionic]

he hum has now greatly reduced, but is still there. I may attempt to move the overhead lighting to another circuit. Its a funky setup, garage electrical, kitchen and dining room light, plus the living room plugs all on one breaker.

Are there any dimmer switches within this circuit?

 

[regore]

I agree . I've cured many hum issues by just reversing the ac plug in the outlet. Mainly with vintage tube equipment though. I have two outlets 8 feet apart but they're both fed from opposite sides of a 220 volt line. I now use a power strip and one ac supply. If I hear thunder only one plug to pull. Dimmer switches can also be a nasty RFI source. Better quality dimmers have RFI supression built in.

 

[WaynerN]

That you can extinguish the hum by lifting the ground pin on the amp does make it seem as if there is a ground loop, but the fact that the hum isn't there when the lights are off makes It is unlikely to be a ground loop within your audio system itself.

Agree that florescent lights can be noisy, but since lifting the ground pin on the amp extinguishes the noise, even when the lights are on, suggests that the florescent lights are polluting the ground when they are on.

Perhaps there is something wrong in the way those lights are wired, such as tying common and ground together? Just guessing here.

Common and ground are always tied together.

 

[WaynerN]

When the ground pin for said amp is removed.

What in the name of electrical science is going on here?

I should add, the hum only shows its ugly face when the flourescent kitchen lights are on. Same circuit as the living room.

How many components in your system have a ground pin? 1 is not even needed.

 

[Gazdatronik]

How many components in your system have a ground pin? 1 is not even needed.

The amp does. The old amp acted the same way and didn't have a ground pin. Every amp I have ever used with the exception of a mundane Technics AV reciever from 2000 did this.

The lighting situation will take a little longer to figure out due to the three way switches used for both the dining room and kitchen light. The garage light also is a three way but does not seem to affect the sound.

 

[rothwellaudio]

The system is powered by two receptacles about 8 feet apart, I have moved all the devices to a single plug. The hum has now greatly reduced, but is still there.

Yes, that certainly suggests a ground loop. The noise picked up is depends on the loop area, and after reducing the loop area by using a single outlet the noise is now reduced. Cables are twisted together for the same reason - to reduce loop area.

 

[Bill Ferris]

Its a funky setup, garage electrical, kitchen and dining room light, plus the living room plugs all on one breaker.

,

 

[Gazdatronik]

,

Its not that bad, the living room was once a master bedroom, and was never expected to carry much more than a couple of lamps an a clock radio, and the garage power only occaisionally used. Washer has its own 20A plug out there.

I doubt I am pulling many amps even now, but having a separate breaker would be great to diagnose things.

 

[Bill Ferris]

Its not that bad, the living room was once a master bedroom, and was never expected to carry much more than a couple of lamps an a clock radio, and the garage power only occaisionally used. Washer has its own 20A plug out there.

I doubt I am pulling many amps even now, but having a separate breaker would be great to diagnose things.

And the/a power circuit isolation can benefit the performance of sensitive equipment..

 

[Gazdatronik]

So apparently it was the kitchen light ballast the whole time.
It wasn't a really old ballast but the new one is pretty much silent. Even the Jazz Bass is quieter.

 

[Lux Man]

So apparently it was the kitchen light ballast the whole time.
It wasn't a really old ballast but the new one is pretty much silent. Even the Jazz Bass is quieter.

I just love threads with conclusions, "especially" successful ones. Thank you for posting your find!

 

[KentTeffeteller]

I just love threads with conclusions, "especially" successful ones. Thank you for posting your find!

Bad ballasts cause much EMI, RFI, and Ground Loop noise and hum issues. Jolly good fix!

 

[tadawson]

Common and ground are always tied together.

Only at a single point at the service entry. Anyhing else is a code violation . . . .

 

[coonmanx]

So apparently it was the kitchen light ballast the whole time.
It wasn't a really old ballast but the new one is pretty much silent. Even the Jazz Bass is quieter.

Thanks for updating with the solution.