John Sayers' Recording Studio Design Forum Archive

Hey folks. Upgrading my studio. I have had terrible grounding and dirty electric issues for some time. Now that I am expanding the space, I figured it was time to fix the electric once and for all. Biggest problem has been TERRIBLE guitar hum.

I had a dedicated panel added to the space. The electrician discovered that the previous home owner had run a Hot Tub from the breaker panel in my garage (the home electric panel) through into the basement and through the space I am expanding to. Since I don't have a Hot Tub he asked if I wanted to use this "wire" to my new sub panel (dedicated for studio) instead of running a new one. He said it was perfectly acceptable and save time and money. Can't say what gauge but it is 3/4" round...pretty thick. So the photos below show the panel and it's wiring.

4 wire Romex runs to each outlet which includes the ground which is wired to an isolated ground bar. The ground bar goes to the outside of the house which is the one green wire shown going outside. The foam insulation is filling old plumbing lines from the old sprinkler system controls I remove, but as you can see I used one of the plumbing exits to run the ground wire through to the outside. There we drove in (2) 10' ground rods, six feet apart.

The photo showing the two outlets is standard home electric on the left in the two outlet box and the new "star grounded" dedicated studio electric is in the four outlet box on the right. I have plugged all of the audio gear into the dedicated studio electric.

I thought that my problems would be over...but it's not. I am sure there will be benefits to adding the new electric and I am glad I did but I REALLY hoped it was going to stop guitar players from looking at me with a look of "are you kidding?" when they plug in, not to mention how painful it is to listen to. guitar grounding buzz/hum.

When you walk out of the room the hum eases up...but doesn't go away completely. When you point the pick ups to the standard light dimmers and get them real close the buzz is really amplified. In addition it gets noisy when I get them close to the CRT monitors.

I am also showing photos of the various ceiling lights and dimmers that illuminate the entire basement.

Would those "in the know" take a look at my photos and verify I have installed a proper system, star grounded for my studio? Then advise or support my theory that the next logical step is to change the dimmers in the control room to a "specialized" dimmer for such applications? &...that the replacement of the CRT monitors to LCD flat screens would also reduce the nasty guitar hum?

Thanks so much in advance.

Ross H
Maryland

Although I'm not an expert, let me ask a few questions:

Are your lights of the low-voltage variety?

Does your guitar hum when plugged-in direct to a mic-pre?

When your CRT monitors are off is the hum acceptable?

When everything is unplugged, (except the guitar amp), is the hum acceptable?

When the guitar player stands in the other room (as you mentioned) is the hum acceptable?

What exactly is wired to your new panel (list each breaker)?

Ok I'm not an electrician so hopefully one more qualified than me will chime in here.

I think I'm seeing a couple of problems in your new box.
It looks to me like all your grounds are isolated from the neutral bus entirely and exit to the additional ground rod, is this so?

From my understanding when wireing a sub-panel the grounds and neutrals have to be seperated untill they bond at the main panel, where the main ground also connects. Your box provides no safety whatsoever, in the event of a direct short to your new grounds the breakers will not trip. I'm pretty sure you can only have one bonded ground as well.

It kind of seems to me like your electrician doesn't know his code, Wireing a sub panel by code would require a 4 conductor cable (2legs of hot, a neutral, and a ground wire) in order to seperate the ground and neutral till the main panel. Your hot tub wire cannot be used. Maybe it can with an additional wire run alongside it, or possibly omit one leg of power and use the other wire for ground. I'm not sure what the codes say about this though so I'd suggest you check with your municipality or anouther electrician. This is a serious issue.

This could also be your cause of hum as there could be a large voltage potential between the common and ground system, creating a major ground loop with two big paths to ground.

Let us know.

Ok I'm not an electrician so hopefully one more qualified than me will chime in here.

I think I'm seeing a couple of problems in your new box.
It looks to me like all your grounds are isolated from the neutral bus entirely and exit to the additional ground rod, is this so?

From my understanding when wireing a sub-panel the grounds and neutrals have to be seperated untill they bond at the main panel, where the main ground also connects. Your box provides no safety whatsoever, in the event of a direct short to your new grounds the breakers will not trip. I'm pretty sure you can only have one bonded ground as well.

It kind of seems to me like your electrician doesn't know his code, Wireing a sub panel by code would require a 4 conductor cable (2legs of hot, a neutral, and a ground wire) in order to seperate the ground and neutral till the main panel. Your hot tub wire cannot be used. Maybe it can with an additional wire run alongside it, or possibly omit one leg of power and use the other wire for ground. I'm not sure what the codes say about this though so I'd suggest you check with your municipality or anouther electrician. This is a serious issue.

This could also be your cause of hum as there could be a large voltage potential between the common and ground system, creating a major ground loop with two big paths to ground.

Let us know.

Sorry bout the double post.

It's hard to tell from the pics, so I might have jumped to conclusions.

Can you follow where the hot tub wire comes in and see if there is a bare ground wire? And see if it attaches to the ground buss.

I will investigate your concerns and report back. While you may not be an "electrician" you appear to have a proficient understanding of electric. You now have me very worried...if anyone else can confirm or deny this intial thought it would make me either sleep much better or immediately pull "the plug" on this panel.

Ross

The Hot Tub wire DOES have a bare copper ground wire coming into the sub panel and is connected to a "bar" on the right side of the panel. If you look at my photos above, the last photo on the page (bottom right) shows this ground wire attaching to the "bar". I assume it is the ground bar you speak of as it has four other bare copper grounds attached to it as well.

With that said I would hope to confirm the Hot Tub wire is a suitable connection to my homes main panel and is not the potential safety concern?

Assuming the Hot tub cable IS adequate and installed properly, does this eliminate the ground loop potential that I believe was a theory based on NOT having the ground in the Hot Tub wire?

If both of these are no longer an issue I would like to move back to the original question as to whether or not my next logical "corrections" are with appropriate dimmers. I can purchase two "studio" dimmers (WBD Luxtrol 8500) from a facility closing down for $250.00. I am ready to purchase if it seems like I will get the benefit.

The question I have regarding the dimmers is they will be installed on the electric of the rest of my home and not the new studio panel. Therefore, will switching out the two regular dimmers in the control room to the Luxtrol's resolve my dimmer problem considering there are so many other dimmers in the house and in the basement?

Ross

Ross

Ok, Glad to hear the hot tub wire is correct.

Yes the hot tub wire can be used, however your isolated grounds on the left of the panel are not connected to the neutral bus. This is where the safety concern lies, most codes, when installing a sub panel require the grounds and neutral to be seperated untill the main panel where they will be connected there as well as the main ground cable-ie ground stake or whatever.

In order to make your panel safe/code happy you could easily move the 4 green ground wires from the buss on the left side of your panel and connect them to the other ground buss on the right -the one with all the bare wires attached. as for the extra ground rod and cable installed on your sub panel, I think youll have to check your local codes, some allow it some don't iirc.

I would try this first before the dimmers, as I believe you could be getting some voltage potential diff on your isolated grounds by not having it connected to the neutral buss. The neutral buss/ground system is critical in the operation of our power system, The neutral has to be connected to ground and especially from the same points as your other grounds, this keeps the neutral always at 0 potential and your grounds operating properly.

Please fix the grounds first as I think its not only a safety concern but will probably fix your noise issue as well.

PS even if your code allows for the extra ground rod, I'd try it both ways to see which one works better.


Keep us up to date.

Erik

One last note.

I forgot, and I'm sure you know this already and are probably rolling your eyes as you read this, but make sure you turn off the main panel breaker to your sub panel before working.

ok, I can sleep tonight.

Aloha Ross,

I have no wisdom here, but here are a few links on dimmers that might prove useful to you (courtesy of Aaron.)
http://www.superiorelectric.com/PDF/Lux ... ntrols.pdf
http://variac.com/staco_Variable_Transformer_Map.htm
http://www.lutron.com/grafikeye/3545.html

Hope this helps,

Aloha

Greetings all.

Been a little busy this past week and hadn't been online much.

It almost looks like your using 2 separate grounds. Typically those rails on the side are tied together as a neutral. And it looks like you have grounds going to the neutral on the right.

Is the large green ground wire going to a separate rod or back to the main panel? Is the black, red and white going to the main panel I assume...what amperage breaker are you using? Is the copper wire connected to the bar on the right going to where in the main panel...neutral or ground?

Is the neutral and ground bonded at the main panel?

Check and see if you have any voltage across your neutral and ground w/ a meter.

I think his neutral bus is on the left, ground on the right, and ig far left.

I can't tell from the photo, but I know mine is neutral bars on both sides.

I am using seperate grounds. The main panel in the home has a ground and the sub panel has a isolated ground as well.

The large green wire on the left side of the panel is going outside to two 10' ground rods, six feet apart.

The Black, White and Red wire is going to the main panel. It is a 50 amp breaker in the main panel. The copper wire connected to the bar on the right in the sub panel is going to the bar on the left in the MAIN panel which I took a photo of and attached.

I can't answer the question about whether or not the neutral and ground bond at the main panel...what do I look for, or can you tell from the photo of the Main panel? I asked the electrician this question and I "think" he said yes it was. The elctrician said he will stop by later in the week and double check all connection and put a meter on the box as suggested.

Any other thoughts would be welcomed...

Ross

The house main panel...dotted line is drawn in to show ground path.