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I need to choose a single ground: Projector or Onkyo TX-SR705? (1 Viewer)

Rancho5

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My HT will have three circuits: Lights/Recepticles, Projector and then Audio stuff using two runs of 12-3 wire.

So I have a choice on grounds. Two of these will be a shared (common) ground and one grounded by itself.

One of my electrician friends suggested that the projector be on it's own ground so there will be no interference or static if we run the vacuum during the movie, etc. Which chances are zero.

But I do have an Onkyo TX-SR705 (in the box waiting to be installed when ready) and I understand that some Onkyos have a hum problem if they have a common ground.

So which would you choose to have on it's own ground? Projector or receiver?

I'm leaving tomorrow for 3 days for a funeral so I look forward to reading your responses when I return.

Thanks guys!
 

werty7777

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I'm just a simple builder with limited electrical knowledge, however all grounds are essentially shared in the panel in the first place. Furthermore "static" generally only affects speakers with powered subs if any at all. So long story short as any electrician I know would tell you is don't share lights with any other components period. But you know that already. What audio stuff are you connecting? Which projector are you installing? Generally speaking receivers have great insulation properties as it pertains to electrical noise and any decent power conditioner would solve the any worries you may have. So with all this rambling I would say leave the projector on it seperate ground because any electrical noise is more noticed visually versus audibly. Hope this helps. Sorry to hear about the funeral and good luck on the install.
 

Leo Kerr

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In my mind, the lighting isn't always a clear-cut answer.

If the lights are regular incandescent lights that aren't dimmed, then it doesn't matter where they go.

If they're incandescent that are dimmed, fluorescent, metal halide, or some other "ballasted" light, then they need to be off in their own little electrical world.

Leo
 

Rancho5

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Loggin in on the Mom in laws PC in Phx.

Thanks for the input so far.

Lights will be canned and sconces on dimmers. The part that werty mentioned about receivers having pretty good insulation properties is what I owuld liek further clarification on. I remember reading that Onkyo's in particular had a problem with "humming". I don't know if it's with my model (705) or not and would like someone with experiece to chime in.

I have a SVS Powered cylindar subwoofer, so yes it is powered. And the projector will probably be an Epson 1080p, (6100?) or similar that retails for 2k.
 

werty7777

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It's really the basic performance of power supplies that "insulates" the receiver. Receiver's, especially when you get to mid level and above, power supplies are made to provide wattage in receivers that is clean power to feed your speakers. Obviously dirty amps can damage speakers by clipping and no legit manufacture would ever want that. Simply put if you weigh your power supply in your projector it would never come close to the weight of the supplies in your receiver. While the power supplies have very different yet very similar jobs the receiver does a better job of "insulating" interference and disregarding (for lack of a better word) any interference that is fed electrically. By the way just upgraded to a Onkyo 876 from a Sony 5200ES and the heat and/or humming problems are no issue here with my entire system on one circuit.
 

chuckg

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How is it that one of your circuits has a separate ground? ALL of the ground wires (and the neutral wires, too) in your house go to the power panel and are tied together. If what the electrician means is that two circuits will share a "leg" then by all means put the lighting circuit on the lonely leg.
 

Rancho5

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Originally Posted by chuckg

How is it that one of your circuits has a separate ground? ALL of the ground wires (and the neutral wires, too) in your house go to the power panel and are tied together. If what the electrician means is that two circuits will share a "leg" then by all means put the lighting circuit on the lonely leg.
I know what you mean...they all share a ground at the panel. I guess it is sharing a leg. Did you mean to say put the lighting on the lonely leg or did you mean the projector like everyone else said? Why would you suggest putting lighting on the lonely leg?
 

chuckg

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I've always put lighting separate from electronics simply because the dimmers in those lights are electrically noisy.
 

Rancho5

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Originally Posted by chuckg

I've always put lighting separate from electronics simply because the dimmers in those lights are electrically noisy.
I understand the need to keep them all separate, which is why each one, (lighting, PJ and audio) will all be on their own circuit.

The question was regarding a "shared ground". I've pasted the original question below just to assist.

[SIZE= larger]My HT will have three circuits: Lights/Recepticles, Projector and then Audio stuff using two runs of 12-3 wire.

So I have a choice on grounds. Two of these will be a shared (common) ground and one grounded by itself.

One of my electrician friends suggested that the projector be on it's own ground so there will be no interference or static if we run the vacuum during the movie, etc. Which chances are zero.

But I do have an Onkyo TX-SR705 (in the box waiting to be installed when ready) and I understand that some Onkyos have a hum problem if they have a common ground.

So which would you choose to have on it's own ground? Projector or receiver?
[/SIZE]
 

chuckg

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There will not be a separate ground....all the ground wires are tied together at the electrical panel.

If you get a hum problem due to a ground loop, the easiest thing to do is remove the ground wire connection at some point - either the amp or the projector. This solves the problem in 99.9% of all cases, and is not dangerous.

If you really must decide whether the amp or the projector should be "on it's own ground" then I would say it doesn't really matter...
 

Speedskater

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I'm a week late on this but, in North American 12-3 cable has 4 conductors. Hot (A), Neutral, Hot (B) & Safety Ground. Much residental wiring uses 12-2 cable which has 3 conductors. Hot, Neutral & Safety Ground. I like the idea of using 1 main 12-3 (or maybe 10-3) cable for the complete audio/video system. This will keep all the equipment referenced to the same neutral and safety ground.
 

industrialarts

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Just to chime in here - a 12/3 cable has 3 conductors of 12 gauge wire. Likewise, a 12/2 has 2 wires of 12 gauge.

If possible, you should drag all audio & video grounds individually from each of the receptacles to a common ground connection and keep them on the same AC phase. If you have flourescent or dimmed lighting, it would be helpful to keep that off the A/V phase.

Also, use the 3rd pin ground on all A/V equipment that has it. If you have hums and buzzes, lifting the 3rd pin is not a good choice.

Use good surge protectors on all the gear and a UPS for anything with a microprocessor (which is pretty much everything - excluding the power amps).

Mark Springer
industrial arts
 

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