Sub hum / buzz from florescent lights :(

[jinjuku]

I hooked up my sub and there is a hum with the florescent can lights on. The projector is on the same circuit with the lights.

Obviously the hum wasn't there watching the Oscars last night because the lights were out. Soon as I turned the lights on: BUZZZZZ

If I pull the HDMI out from the projector the buzz stops (or I turn out the lights)

My new curse phrase: BOB SAGET! (trying to alter my vocabulary with a kid coming).

So what outlet could I install on the PJ to get rid of the hum or do I need to switch back to incandescent bulbs (I know, take care of the problem don't mask it).

 

[jinjuku]

update...

So I turned the lights back on and one by one unscrewed them. The buzz went down but not away. Turned the light circuit back off and the buzz stayed the same. Very low but still audible.

So I am maybe looking at trying to pull another 14/2 line just for the PJ unless I can get an outlet with filtration that will take care of it.

It's not the CATV. The line feeding the lights is a 14/3 line with a shared common and neutral. I think I knew better. Ugh...

 

[Chu Gai]

Are these CFL's that are on dimmers?

 

[jinjuku]

No, just CFL's on a on/off switch. I have the buzz down to in-audible levels if I put the receiver on the same circuit with the amp driving the sub. If I unplug the PJ then it is dead silent.

I am looking at living with it as is since at 2-3 feet away you can't hear it or looking to see If I can sneak another 14/2 line up. But even that is not a guarantee against differences in ground potential, which is why I hesitate on doing it.

MIT of all companies has a single gang outlet with filtration that may kill the noise that is introduced through the PJ.

 

[TLS Guy]

The problem is you do not know if the buzz is transmitted via the mains, or airborne RF.

Can you make a temporary connection to the projector from another circuit?

Also the fact you are getting this may indicate you have some neutral gauging in your house wiring. Fluorescent bulbs are discontinuous loads, and lead to neutral stress. Because of this, and other devices leading to larger discontinuous loads, electrical codes for neutral lines have changed in a lot of jurisdictions of late. A lot of homes are not ideally wired for our current environment and this will become an increasing problem. This will make problems like yours common, with worse and more serious problems to come.

 

[jinjuku]

The problem is you do not know if the buzz is transmitted via the mains, or airborne RF.

Can you make a temporary connection to the projector from another circuit?

Also the fact you are getting this may indicate you have some neutral gauging in your house wiring. Fluorescent bulbs are discontinuous loads, and lead to neutral stress. Because of this, and other devices leading to larger discontinuous loads, electrical codes for neutral lines have changed in a lot of jurisdictions of late. A lot of homes are not ideally wired for our current environment and this will become an increasing problem. This will make problems like yours common, with worse and more serious problems to come.

You and I are on the same page. I may take some 14/2 wire to a breaker and run it through the house to the PJ. Even with a straight home run I may still may have differences in ground potential. Wiring a sub panel is not an option. Tying grounds is definitely not an option.

The wiring is right, I am just dealing with the laws of nature

Or I try the MIT box. Which again is no guarantee. Uhg.

 

[jinjuku]

I have the MIT Z Duplex on order from a supplier that has a 30 day satisfaction guarantee. I will let you know how it goes.

 

[highfigh]

I hooked up my sub and there is a hum with the florescent can lights on. The projector is on the same circuit with the lights.

Obviously the hum wasn't there watching the Oscars last night because the lights were out. Soon as I turned the lights on: BUZZZZZ

If I pull the HDMI out from the projector the buzz stops (or I turn out the lights)

My new curse phrase: BOB SAGET! (trying to alter my vocabulary with a kid coming).

So what outlet could I install on the PJ to get rid of the hum or do I need to switch back to incandescent bulbs (I know, take care of the problem don't mask it).

First, I would never use a projector on a circuit that's also used for lighting. Second, if the buzz goes away when you disconnect the HDMI cable, you have a ground loop. If you can, reassign the projector's power feed to the same circuit as the theater equipment. That alone may eliminate the buzz.

 

[Warpdrv]

You may also want to look at if the Lights are on the same phase as your equipment....

Make sure that all your equipment for HT breakers are on the same lugs, and the lights on the opposite lugs... You may have to pop the breakers out of the box and move them around a bit to get the phasing situated properly. I would try that first if its possible.

Breaker layout such as this...
So the phasing layout looks like:

1 A 2 - A phase
3 B 4 - B phase and so on down the line
5 A 6
7 B 8
9 A 10

 

[jinjuku]

First, I would never use a projector on a circuit that's also used for lighting. Second, if the buzz goes away when you disconnect the HDMI cable, you have a ground loop. If you can, reassign the projector's power feed to the same circuit as the theater equipment. That alone may eliminate the buzz.

I know it's a ground loop... I pulled 12/2 for a 20 amp circuit to drive the Amplification with. The receiver is on a different circuit and even with the PJ HDMI unplugged there is a very minor ground hum. It's just physics at work. Just because you have everything properly grounded doesn't mean that you won't have a ground loop. If I put the receiver on the same circuit as the amplification then the sub is dead silent.

I could put everything on one circuit:

Behringer EP2500
Adcom GFA 5503
H/K 3600
DCX 2496
Sanyo PJ

It should all be ok. I still don't see hitting the 20 Amp wall. Just that the potential is there.

It's not a huge deal since when the PJ is on the Lights are off and vice-versa. It's just that I want that last 2% to be perfect.

 

[Chu Gai]

Or just go with high efficiency incandescent light bulbs from any number of sources like GE, Phillips, etc.

 

[jinjuku]

You may also want to look at if the Lights are on the same phase as your equipment....

Make sure that all your equipment for HT breakers are on the same lugs, and the lights on the opposite lugs... You may have to pop the breakers out of the box and move them around a bit to get the phasing situated properly. I would try that first if its possible.

Breaker layout such as this...
So the phasing layout looks like:

1 A 2 - A phase
3 B 4 - B phase and so on down the line
5 A 6
7 B 8
9 A 10

So basically take breaker that is feeding the circuit that PJ is on and move to the other side of the box?

 

[Warpdrv]

For reasons such as this - Equitech is a pretty neat product that has been used to eliminate ground loop hums and wiring noise issues...

http://www.equitech.com/products/industrial/wall.html

Equi=Tech is a cool company and technology. Their inventions were responsible for amendments to the National Electrical Code (NEC) for Technical Power. I read the amendments before I bought into their products. They use the simple laws of physics to generate clean power (no high-tech band aids, tricks, gimmicks or marketing hype).

They started out making clean power for professional recording studios, then went into mobile trucks for live concerts and then home audio/video. At concerts, the truck would plug into the power grid and the audio would plug into the truck. When the light guys with strobes and arcs would plug into the power grids, the audio lines remained unaffected.

Their 240V version uses 2 phases. It steps that down to 120, but then converts the 120 to +/-60V (2 hots and 1 ground) versus the conventional 0/120V (1 hot, 1 neutral and 1 ground).

Since the differential between +/-60V is 120V, your equipment still sees 120V, but has the benefit of common mode rejection. Since noise on both of the +/-60V lines are 180 degrees out of phase, they naturally cancel themselves out when they reach ground.

Ground theoretically is 0V, but with in practice with 0/120V it is not. With balanced power, the 180 degree out of phase signals cancel themselves out to 0V.

It eliminates ground loops as well.

These things are not even close to being cheap.... just an FYI

 

[Warpdrv]

So basically take breaker that is feeding the circuit that PJ is on and move to the other side of the box?

Moving it up or down or to the other side of the box, just make sure that its not on the same leg as the lights.

You have to look at your box, but like the Numbers diagram shows, moving directly to the opposite side is more then likely still the same phase....

 

[jinjuku]

Or just go with high efficiency incandescent light bulbs from any number of sources like GE, Phillips, etc.

Yep, my other option... Why spend $30 on incandescent bulbs when a $99 outlet may or may not work

 

[jinjuku]

Moving it up or down or to the other side of the box, just make sure that its not on the same leg as the lights.

You have to look at your box, but like the Numbers diagram shows, moving directly to the opposite side is more then likely still the same phase....

Got it... Thanks for the tip.

 

[TLS Guy]

I know it's a ground loop... I pulled 12/2 for a 20 amp circuit to drive the Amplification with. The receiver is on a different circuit and even with the PJ HDMI unplugged there is a very minor ground hum. It's just physics at work. Just because you have everything properly grounded doesn't mean that you won't have a ground loop. If I put the receiver on the same circuit as the amplification then the sub is dead silent.

I could put everything on one circuit:

Behringer EP2500
Adcom GFA 5503
H/K 3600
DCX 2496
Sanyo PJ

It should all be ok. I still don't see hitting the 20 Amp wall. Just that the potential is there.

It's not a huge deal since when the PJ is on the Lights are off and vice-versa. It's just that I want that last 2% to be perfect.

Properly grounded is relative. Audio equipment needs layout and grounding way beyond electric codes in a lot of cases, especially if there are SCR light dimmers and fluorescent lights. If you have noise then you don't have the physics right.

Also in a lot of cases the problem is RF borne and or AC and ground loop issues.

For may studio a followed a plan published by CBC radio Canada which seemed like the best for my situation. Everything is tied together with a star cluster ground plane using 4 gauge copper wire, it really is a rod.

Everything is tied together with this, and also steel conduit which ties in the plasma monitor. The Direct TV system and FM antenna are obsessionally tied in. The ground terminates in three huge 7ft copper rods driven into the ground and tied together. The system is quiet, quiet quiet, especially with my new Marantz AV 8003 which has a signal to noise ratio of 105 db! It also totally rejects air radio frequency RF dimmer noise, which my old Rotel did not quite if there were a lot of SCRs active in the house.

You can see part of the ground plane here.

As systems grow and become more complex, the more obsessional the design of the ground plane has to be.

 

[Warpdrv]

Or just go with high efficiency incandescent light bulbs from any number of sources like GE, Phillips, etc.

I agree with this also...

These new CF's have ballasts in them, which inherently tend to introduce tons of noise back into a system....