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In Reply to: RE: Update on my ground loop posted by DC STEVE on June 26, 2007 at 18:39:17
This means they produce little or no power supply electrical noise. There would not likely be any advantage in noise reduction by running each monoblock on its own circuit. There will still be an advantage to running the power amps from one dedicated circuit and the other equipment from another, to keep the noise from the other equipment out of the power amps.
However, it would be good to understand your hum problem, and have the extra circuit available for future use. I would definitely check the wiring to make sure there is not an error, and have the third circuit moved to the same AC leg as the other two whenever it is convenient. Once you have checked for wiring errors, it would be interesting to try connecting all the grounds together at the outlets, as jneutron suggested (DON'T do this before the wiring is checked!). Another inmate who is a licensed electrician (jea48) has stated in the past that this is OK per code, but you would need to confirm this for your jurisdiction if you wanted to make it permanent.
Please understand that there is a ground loop whether you use one or two circuits for your power amps, or even if you run your whole system from a single circuit. The loop includes your equipment power cords. Adding the dedicated circuits increases the extent of the loop but does not change the fact of its existence. The only way to break the ground loop is to disconnect the AC safety-earth from some of the equipment. This is dangerous and I do not recommend it.
I've got four separate dedicated lines, and have no audible hum. There are two pairs of lines that were added at different times and that were routed differently, so there is plenty of opportunity for hum induction from stray magnetic fields. Do your lines go near any appliance that draws a lot of current, such as a hot water heater? Please also describe the installation of the outlets in more detail. Are they in metal or plastic boxes? In single boxes or a ganged box?
Follow Ups:
We pretty much now know Steve does not have 3 dedicated circuits.
We know that the 2 gang box for two of the 3 circuits is a 3 wire multi-wire branch circuit.
We know that there is only one equipment grounding conductor for both duplex outlets.
We know if Steve plugs in his two amps into just one of these circuits, (one duplex), he does not have the hum problem.
We know if Steve plugs an amp into each of the duplexes he gets a hum...
We have been calling this a ground loop hum....... Hum yes, but maybe not from a traditional ground loop. Any ideas? Your thoughts......
Jim
The Canary amps use choke-input power supply filters, and draw close to sinusoidal current from the AC, according to their web site. This means the neutral current at idle will be very small: essentially the difference between two similar devices made of real-world components.
It seems plausible that this arrangement would cause 60 Hz noise to be induced in the shared ground conductor, depending on how the wires are arranged inside the cable. This explains the problem if there is still a ground loop involving the source component and the power amps. We are assuming all of Steve's components are grounded, but there are some highly-regarded pieces that either use two-wire power cords, or do not connect the ground of a three-wire cord.
My experience is with separate cables for each circuit and does not apply here.
need to update my profile. i've got a pair of canary audio 160 monoblocks (they are awesome!).
ok, so i guess i need to go back and read through that long document, get the polarity check device, and at some point, ask an electrician to move that third circuit onto the same leg.
it honestly sounds really really great just using the two circuits. i probably didn't need that third circuit.
my lines travel along the outside wall of my condo, they don't travel near any appliances. the outlets are installed inside the drywall, using some type of metal box i'm assuming, with oyaide R1 outlets and nylon face plates. there are two circuits in one ganged box and the third on alone by itself. the two that are together are on different legs.
when you say check for wiring errors... i'm assuming you mean the polarity?
It is the Canary amps that use choke-input power supply filters. Your system should be just fine with both of them on a single circuit.
If you don't get the electrician back to install three dedicated circuits, then you can use the one on the opposite leg to power your computer or install a noise filter.
I thought of another question for you. We have been assuming your power amps use three-wire power cords and that the "ground" is connected to the chassis. However, it is possible that someone intelligent enough to use a choke-input filter would also use a two-wire power cord, or install an IEC connector where the "ground" is not connected inside the amp. Can you tell us whether your amps have the exposed metal connected to AC "ground?"
my lines travel along the outside wall of my condo, they don't travel near any appliances. the outlets are installed inside the drywall, using some type of metal box i'm assuming, with oyaide R1 outlets and nylon face plates. there are two circuits in one ganged box and the third on alone by itself. the two that are together are on different legs.
> > > > > > > > > > > > > > > > > > > > > > > > > > >When the electrician first came out to look at the job did you tell him you wanted three dedicated circuits? Very important you used the word "dedicated"...... and not the word "separate".......
Dedicated means a branch circuit with it's own dedicated hot conductor, neutral conductor, and equipment grounding conductor.
A separate circuit means its own hot conductor, but not necessary its own neutral or equipment grounding conductors.
As you have described, two circuits share the same 2 gang cut-in box. The two circuits are not fed from the same Line in the panel. One is fed from L1, the other L2.
My guess is the electrician installed a 3 wire + grd multi-wire branch circuit.
Two hot conductors,
One neutral conductor,
One equipment grounding conductor.
With this type of multi-wire branch circuit the 2 hot conductors share the same neutral conductor. The two separate circuits are required to be fed from the two separate Lines of the panel, L1 and L2. Not good for audio.On a 3 wire multi-wire branch circuit only the unbalanced load will return on the neutral. Example, if circuit #1 has a load of 5 amps, and circuit #2 has a load of 5 amps, then the unbalanced load of the 2 circuits is 0. That means no current will return on the neutral conductor to the source. It also means that both 5 amp loads are in series with one another.
Example 2. If one connected load is 5 amps and the other connected load is 3 amps, then the unbalanced load that will return on the neutral will be 2 amps. 3 amps of the load will still be in series of the two connected loads.
You can check if you have dedicated or separate circuits at the 2 gang installation. Turn off all three circuits. All three circuits? We do not know if the third circuit travels through this same 2 gang box.
* Pull the cover plate.
* Pull the two duplex forward from the box. Note if the wire is solid it will be stiff to say the least. If stranded it will pull out fairly easy.
* Look for the white conductors that attach to each duplex outlet. Do they joint, splice, to a common white coloured wire? If so this is a multi-wire branch circuit. If on the other hand if each white wire that connects to each duplex does not joint with a common white wire and instead enters from a raceway that enters, connects, to the box then the circuits are dedicated.Just an added note. A 3 wire multi-wire branch circuit will also have a shared equipment grounding conductor, You will see the green wired jointed in the same manner as the white neutral conductor.
Even if you indeed do have dedicated branch circuits unless the electrician insulated one of the duplex recepts supporting traps, from the metal 2 gang box, the two supporting straps are bonded together because of the metal 2 gang box. this is perfectly legal.
--------------So if you told the electrician you wanted dedicated branch circuits and he gave you 2 separate circuits in the 2 gang box then he should on his own time correct his error.
i'm almost 100% sure i have the multi-wire branch circuit. i said "dedicated", but then he showed me the 10g romex, showed me the one neutral/ground that would be shared, and i said "ok". so i dont think i can go back to him.
i need to try and find a way to live with it i think. i have two circuits that are on the same leg. can i use a balanced power unit on the third leg for my computer (i'm setting up computer based audio) and router without inducing hum?
if not, i'll just stick with the two outlets. the third one is useless to me, and honestly, with my stereo, maybe the two is enough. i dont have home theatre, i dont see my needs growing, and i need to try and keep costs down. i've already blown a lot on this project.
i'm almost 100% sure i have the multi-wire branch circuit. i said "dedicated", but then he showed me the 10g romex, showed me the one neutral/ground that would be shared, and i said "ok". so i dont think i can go back to him.
> > > > > > > > > > > > > > > > > > > > > >You said "Dedicated" obviously you did not get Dedicated. You are not an electrician you do not know exactly what wiring method is involved for a dedicated branch circuit. You do know that a dedicated branch circuit has its own dedicated Hot, Neutral, and Equipment grounding conductor.
Did you tell him you wanted the three dedicated circuits fed from the same, leg, or side, or LINE, of the electrical panel? He knows a multi-wire branch circuit can not be fed from the same Line.This guy charged you, I believe you said, $170.00 per hr. He represented himself as an electrician knowledgeable of audio equipment.
I would give him a call. I would tell him you get a ground loop hum when you use both circuits from the 2 gang outlet box. I would then say, "I asked you to install dedicated circuits?".... then pause allow him to answer...If he says, "That is what you have, that is what I wired".... Then ask him if that is what you have that means each dedicated circuit has its own dedicated hot conductor, neutral conductor, and equipment grounding conductor...... Wait for his response before you say anything else.To be honest with you, the guy probably is a good electrician. But he is not an Audio savvy electrician. No electrician with a background in Audio would install a multi-wire branch circuit, two 120V separate branch circuits.
For what he charged you, you could of looked in the Phone book Yellow pages and hired a NECA/IBEW electrical contractor for far less money. A contractor licensed, Bonded, and insured.Post back if you call the guy that did your electrical work. Let us know what he said.
If the DC in Steve's moniker means District of Columbia, then he would not be able to hire an NECA/IBEW electrical contractor for less than $170 and hour. I live in Arlington, VA and, coming from SC, am still pissed off every time I get a quote from a contractor of some type. Needless to say, I end up doing a lot of the work myself. The latest quote was to install a gas water heater (in a location 5 feet from the old one) for approximately $2,000. Give me a freakin' break!
Louis
If so, a lot of the cost is for standing around waiting for the inspector.
They wanted $800 to do some water piping that would have cost about $150 in Greenville, SC. Evidently there are a lot of people around here with a lot of money who pay such prices, because none of the contractors care whether they have your business or not--they are plenty busy without you.
I don't know how reliable the building inspector is in your area. We have a good setup here, where you can make an inspection appointment through an automated phone system. The inspector showed up right on time and signed off the job quickly.
If your contractor has to wait for a day or two for the inspector to show up, I can understand the high bid.
If they were building anything else into the price related to the inspection, then they didn't itemize it, and, in fact, made it to look like the fees specific to the work being done. Ultimately, some "waiting around" money could be built in, but nothing was said of it.
i'll call and talk to him. i've spent so much on this, the thought of spending more is not appealing at all. i went with a consumer rated electrician, not just anyone our of the yellow pages, i thought that would mean i get what i need. obviously not. i'm kind of upset by the whole thing. bit what's the big deal w/ just using the two lines and calling it a day? i mean, shouldn't i cut my losses here?
Steve As for the guy that wired your branch circuits I would not pay him another dime......... I contend he should know the difference between a dedicated and a separate circuit.As for the 3 wire multi-wire branch circuit you have now, if you only use one of the two circuits that would basically be a dedicated circuit. So you have two dedicated circuits. Just make sure the one you use is fed from the same Line as the single duplex dedicated circuit. As for the odd ball separate circuit.......see if the electrician that did the job will at least come to your home and either move the circuit in the electrical panel to the SAME breaker as the good circuit, or disconnect the oddball circuit from the breaker and at the 2 gang outlet box rework the two duplexes so they will be fed from the good circuit. This will give you a dedicated 4 plex.
As for connecting your computer to the other separate circuit imho you power amps will suffer, imo. Computers are filthy beasts when it comes to the junk they put back on the AC line. Remember on a 3 wire multi wire branch circuit only the unbalanced load will return on the neutral conductor to the source. That means the rest of junk on the current of the computer would be in series with the power supplies of your power amps. Kind of defeats the purpose of the new circuit don't it?
ok, i think i can get him back to move that separate but not dedicated circuit onto the same leg. is there a way he can fish a new ground wire for that separate circuit, to make a dedicated circuit?
as for the computer... not sure what to do here, i'm setting up a music server. where do i put this? outside of these separate/dedicated circuits?
sigh...
If you can plug it in to another circuit, that would be the best. If you have to use your spare circuit, isolate the computer with the best filter you can find.
You may also want to plug a damper such as the Quiet Lines unit into the spare circuit if you are going to use it, or switch its breaker off if you are not.
I have the CA160's myself, along with the CA903SE (4 box) preamp. Good stuff!
Louis
yes, i love the amps!! awesome! i think i'm just going to use the 2 dedicated circuits. the third isn't useful for me, maybe i just plug in some blue circle noise hounds on that extra outlet...
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