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The Downside to Dedicated Lines vs. the Benefits

From an AC power grunge perspective, my main system currently seems very quiet. That is, I don’t have any ground hum issues, and I have to raise the gain fairly high and then get my ear quite close to one of the speakers before I can detect any hiss or other noise. It is truly the quietest system I’ve ever had experience with. Never the less, I do know that paying attention to AC power issues can reap other benefits, including an improved soundstage, imaging, better dynamics, etc.

I built this system from the ground up about a year ago and am now at the phase where I’m beginning to work on optimizing it. Back when I started planning it out, there was no question that I would be putting in a couple of dedicated lines. However, now that I’m at the point where I’m about to begin the project, and after a ton of reading and research, I’ve begun to have some serious reservations.

My concerns are mainly over the potential for introducing (or increasing) ground or ground-loop noise and/or hum. From what I can gather, powering interconnected components (especially non-balanced, or single ended, components) from multiple circuits, whether dedicated or not, raises the risk of this occurring.

I also understand the type of components as well as the system’s overall configuration plays a part as well. If I could summarize the details of my system and get some opinions about whether I run the risk of messing with an already good thing, I’d be very grateful.

The majority of my gear sits in a metal rack (Middle Atlantic) in an enclosure located directly behind the front wall of my listening room. XLR cables feed through the wall to a couple of mono amps that sit in the listening room near the speakers. The system currently doubles as a HT and 2ch rig and, as with most folks here, will no-doubt evolve and experience its share of equipment changes. As such, there’s a good chance I may not have a fully balanced system at any given point in time.

Right now, all of the audio gear, a cable box, an active sub, and a 60” plasma TV run off of one 20 amp circuit. There are various other wall-wart devices using the circuit as well (computer switch, rack fan, the receiver for my RF remote control, etc.) There might be a couple of incandescent lights that run on it too, but no other devices or equipment.

Everything currently runs through a couple of top-of-the line Belkin ‘Pure Power’ UPS/Surge Suppress/Conditioning units. Plans always were to repurpose these units after the dedicated lines were installed. However, considering the virtual lack of AC grunge despite all that’s plugged into them, I’m amazed at what these units are capable of.

If I do go ahead with installing the dedicated lines, I would put in a 100 amp sub-panel in the room that houses the rack. I’d need to pull about 80 feet of wire back to the main panel. (BTW, I don’t know much about the electrical trade, so if someone could offer guidance on what type of cable and gauge I should run, I’d appreciate it.) I’d then run 10/2 cryo’d romex (just because) out to three or four audiophile grade duplex outlets. Unfortunately, with where I’d be putting the sub panel, an isolation transformer wouldn’t be practical.

I would like to keep the existing branch circuit in place, and plug all the non-audio gear into it via the existing Belkin units (wall warts, cable box, TV, etc.) The front end equipment, sources, sub, and amps would go on the dedicated lines… directly at first…but eventually I’m sure I’ll end up trying one or two of the better power conditioners that are often sold here on Audiogon.

Now…from all that I’ve read, it appears that the above configuration could be prone to ground noise/hum issues. If I’ve correctly understood a publication that Middle Atlantic has out, a large part this potential comes from the fact that the metal rack serves to interconnect all the components stored in it.

What I’m concerned about is this. Since these interconnected components will be plugged into different circuits…i.e., a branch circuit that terminates at a panel 80 feet away, while the rest will use dedicated circuits that terminate a few feet away at the sub panel….will I end up with ground loop noise issues? As I said, the system is already very quiet and I would hate to lose more than I would gain.

Is there any wiring strategy that might help avoid it? I’m not sure I exactly understand the concept, but if I told my electrician to ‘star ground’ the dedicated lines, would that be enough? Should I instead think about putting the subpanel closer to the main panel? On the other hand, would it be better to not risk it and instead invest in one of the uber-top of the line power conditioners, or perhaps a power regenerator?

Whatever opinions or advice I can get from the Audiogon community would be appreciated.
shutterman

Showing 7 responses by shutterman

shutterman OP
7 posts
 
"I'm not aware of any "downside" to using dedicated lines.
I do, however, suggest installing two lines -- not much more trouble really -- and then you can separate components as you wish - i.e: front end/amps, digital/analog, motors/electronics, etc."

Well...the downside is the increased potential for ground hum or noise as stated in my post, so I'm not sure I fully understand what you mean. Are you saying that you don't believe such potential exists? If so, I'd certainly like to believe you are correct. However, based on posts from the archives here and on articles posted other places, I came away with the impression that the potiential increases in configurations as the one I cited above.

Regarding the recommendation for two lines...yes, as I stated, plans are for at least two. I would have to have at least two as the amps are in one room while the rest of the equipment is in another.
shutterman OP
7 posts
 
"The more components you connect in this fashion, the more ground loops you create. For this reason, it is best to use one lare circuit to feed your system rather than several smaller ones. If you use a line conditioner - as you should - buy one that will handle all of your equipment and run a dedicated line to that. Then plug everything into it."

This is certainly the impression I too have come away with in my readings. This is probably why I don't have any ground hum issues with my current setup. While it is not a dedicated line per se, all the equipment IS plugged into one circuit.

Your comments and the link Danielk provided to BAT Technologies FAQ page (thanks, Danielk!) have started me thinking that using one line to feed everything might be the best solution in my case...especially since the metal equipment rack interconnects a good portion of the gear.

However, my difficulty in doing this is that I have the mono amps in one room, and the rest of the equipment in another.
shutterman OP
7 posts
 
Swampwaker…Thanks for pointing out the wording in that section. It made me think about exaclty how the equipment is loaded in my rack. Each piece is, in fact, not bolted to the rail. However, each piece is pushed up against a custom cut metal face plate that MA sells. These faceplates are then bolted to the rails. I started out using the insulating washers, but they were somewhat "fiddly" to deal with, so I wound up with just a few of them. I'll now probably go back and make sure they are installed on each one.

And…just to provide a little more assurance against a ground loop from forming, I think I’ll abandon the idea of trying to use the existing branch circuit coming off the main panel to power the non-audio gear. Seems like it would be better to simply install an additional circuit or two off the sub-panel.

Jea...no, I wasn't planning an isolated grounding scheme. However, just out of interest I read up a bit more on the subject last evening and have a better understanding of its commercial application. I see now that MA's white paper is, as you pointed out, geared more toward that type of install.

The 80' back to the panel is the up, down, and around estimate. Estimate includes some slack, so the feeder wire could turn out to be shorter. For the circuits off the sub panel, I estimate the longest run to be about 20', shortest run could be as little as 8', depending on cross stud placements we encounter in the wall. That is…unless there is an audible or electrical advantage to keeping the runs the same length?

The deal I have with the electrician is that I will buy and have on hand all the materials. Consequently, I’m doing my own research on what all will be needed. Concerning the sub panel… I started out thinking a Square D QO product, but think I’ve instead settled on a 100 amp Cutler Hammer CH panel. According to their product literature, the CH series uses a “Single-Piece Silver Flash-Plated Copper Bus”

My main panel is a CH 200 amp box. I have only two-breaker slots left available on this panel, which is the reason for the sub-panel decision. I have 20 amp breakers in the main, and I plan to use 20 amp breakers in the sub panel also.

One question I haven’t nailed down as yet: Do I need to buy both a 100 amp (or, perhaps the 60-70 amp you mentioned) breaker for one of the two available slots on the main panel AS WELL AS a 100 Amp main breaker at the sub panel?

BTW, thank you for your tip about making all the wiring for the circuits off the subpanel the same AWG. I had thought about using 10/2 for the mono amp circuits and 12/2 for the rest. Your advice about not using a mixture of AWG is appreciated.

A couple of final questions if you don’t mind…with a 100 amp subpanel in mind, the electrician had recommended a #3 AWG copper cable for the feeder line. I assume this means a 3 conductor solid core cable with safety ground wire…right? That is, when I give the big-box store man my order, I shouldn’t have to specify much else? In other words, I don’t need to purchase a separate ground wire also?

As far as trying to keep everything in the sub panel on the same leg is concerned…since it is being fed from only one leg off the main panel, does this mean that each and every breaker row in the sub panel is therefore also on this same leg? In other words, there’s no need to skip breaker rows in the sub to ensure the all the audio gear is fed from the same leg?
shutterman OP
7 posts
 
"You may run into a ground loop hum. If you do purchase a www.jensen-transformers.com/ isolator. I had hum from a powered subwoofer and the cable tv cable"

Thanks...appreciate the link. I knew there were other humbusters out there, but I just didn't think about Jensen. My impression is they make some quality stuff, so this will be a nice link to hang on to. However, I'm hoping to find a way to do the dedicated lines and end up not having the need for something like this.
shutterman OP
7 posts
 
"The trick to eliminate ground loops is to run all of the lines powering your equipment to the same phase (leg) of ground in your fuse box. It is also a good idea to isolate all of the "noisy" lines on the other phase from your equipment. Your electrician should understand this readily."

Understood. However, in the configuration I've detailed above...wouldn't the fact that I'd have interconnected equipment (via the metal equipment rack) on a mixture of a branch circuit plus dedicated curcuits still not cause an issue?

The existing branch circuit (which will continue to feed the cable box installed in the rack, the plasma TV in the other room, the wall wart devices, etc.) is terminated and grounded at the main panel 80 feet away. The dedicated lines would terminate, and I assume be grounded at, a subpanel less than 10 feet away.

I understand that the subpanel itself is then grounded back to the main panel, but wouldn't I still essentially end up with interconnected components (via the rack) sharing two different circuits...circuits that are initally gounded at two different places? If so, wouldn't this establish a large ground loop?

As far using the same phase or leg is concerned...as long as I tie the sub panel to the same leg that the branch cucuit is on, will everything in the sub panel then be on the same leg? Or should I alternately space the wiring(i.e., skip a breaker row) within the sub panel?
shutterman OP
7 posts
 
Thanks for weighing in Jea, as I know from your posts that you've been around the block a time or two with this sort of thing.

Unfortunately, I think your opinion lines up with mine and gives me reason to believe that a multiple circuit (dedicated or not) might cause more issues than it would solve.

BTW, I noticed your comments were specific to equipment connected via IC's. What about the notion that in a metal rack, ALL the equipment loaded into it is interconnected...whether interconnects are present or not? Or am I reading too much into, or not properly understanding,this publication from Middle Atlantic?

http://www.middleatlantic.com/pdf/PowerWhitePaper4_07.pdf

One blurb that jumped out at me (pg 29): "A problem will exist due to the fact that all equipment with a 3-prong (grounded) plug has the power cord ground conductor bonded to
the chassis. When this rackmounted equipment is screwed to the rackrail, an inadvertent ground connection will be present, defeating
the isolation!"
shutterman OP
7 posts
 
Are you feeding the sub panel with 120V only or 120/240V?
If 120/240V every other breaker down each side is the same Line, leg.
Hmmm...good question. When the electrician scouted the job, he took a quick look at the panel. He said that he would use one of the two vacant slots in the panel to tie the feeder line to. Don't know if he specifically checked the info on the panel door or not, but it was he that came up with the recommendation for a 100 amp sub panel. He told me specifically that I'd need to get a 100 one-way amp breaker for the main panel. (I take it that he meant a single pole 100 amp breaker.)

He also said that I should have a 100 amp main breaker in the sub instead of a lug only load center. But after thinking about it later, I couldn't see the need for it, so that's why I threw the question out here.

I thought because he would be tying into only one place on the main panel...using only a single pole breaker...that this meant the feeder line was tied to only one leg, and therefore only 120v. On the other hand, he did specify the feeder line needs to be a 3 conductor wire, so perhaps he does intend to feed 120/240V? If so, I'll be sure to use every other breaker in the sub panel in order to keep everything on the same phase.

I think my next step is to work out some of the above details with the electrician that's going to do the job. No need to expect folks here to take up anymore of their time to help fill in gaps that I can run down by other means. However, I couldn't have got this far without the help of Jim (Jea) and others who provided guidance. Nice thing about forums with decent search engines like this one is that threads like this can help other folks down the line for a long time to come.

I think I've learned that while there's a strong argument for using only one dedicated circuit to feed all interconnected equipment, others find advantages in having all analog and all digital on separate circuits. If a single dedicated line isn't practical, it would seem adviseable to at least branch all lines for interconected components from the same panel in an effort to avoid ground loop issues. Wiring phase for both the lines and the equipment is an important part of the equation and needs to be checked. And finally...in spite of what smattering of knowledge a laymen might gain, wiring in additional electrical capabilites is serious business that's best left up to a certified pro.

I'm sure there are several other points others have made that I failed to mention. I'm also sure there are a dozen other aspects that haven't been brought up, so if anyone wants to chime in with other pointers, I'm certainly willing to listen.
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