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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 1 response by inline_phil

inline_phil
11 posts
 
You are correct in your concerns. Improper grounding creates ground loops not only internally to the circuit but also from component to component. Fortunately today, most high end equipment manufacturers have learned what the medical industry has known since the introduction of electronic scalpels in the 1960s.

A ground loop is any grounding scheme that can take more than one path to reach earth. So if your preamp and power amp both use a 3-wire grounded plug and you plug them into different electrical circuits and then you ground them to each other with your interconnect cables, you have by definition a ground loop.

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.

Now this assumes that the transformers inside each piece of equipment have been properly tested and wired for lowest line leakage (properly phased) upon assembly by the manufacturer. Easy to check. Unplug everything from the component and lift the ground wire from that component by using what's called a "cheater" plug. Plug the cheater into the wall outlet and measure the voltage from the ground wire to earth ground inside the wall outlet. Then reverse the polarity of the cheater plug in the wall outlet and measure this voltage again. If the voltage lowers in the reverse direction, the power transformer phase inside that component is wired improperly and should be reversed. Do this for each component and all will be well in OZ.

Even those components using two-wire plugs can have this phasing problem. A similar scenario can be used to test ground leakage voltage by measureing from a circuit ground of the component to the wall outlet (use a ground pin on the component or the shield of an RCA plug).

Balanced component systems have an advantage over single-ended (RCA style) systems here in that they use additional electronic wizardry (called the common mode rejection ratio) to again lower the influences of ground loops and other stray electrical influences imposed on the interconnect cables.
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