I have a ground loop that's been killing me for weeks. I've tried several things to limited or no success. I've written to Mike Sanders at Quicksilver, but I'm a little chagrined to keep asking him questions that aren't really the fault of his gear.
Anybody want to have a go at solving this puzzle? It's driving me nuts, and I'd be grateful for any help.
Amps, preamp, and sub are all plugged into a Monster 2000, so everything shares a common wall outlet. Plugging the amps into separate wall outlets has little effect either way. Amps are damn near dead-quiet with no input, so it's shouldn't be the transformers or the tubes.
Amps plugged in to the preamp (shielded DH Labs RCA cables) hum, and the sub does too. Swapping cables has no effect. Unplugging and reconnecting sources (a turntable and a Mac Mini via a Schiit DAC) has no effect. Unplugging the sub has little effect (except it eliminates the hum in the sub, haha).
Lifting the ground on the amps reduces the hum — by about half, but definitely not completely. A Hum-X has no (or very little) effect, whether placed on the preamp, an amp, or the sub.
For obvious reasons I don't want to lift the ground on the amps permanently.
I'm not an electrical engineer, but I'm a logical guy.
Ideas? I'm open to any with two requests: First, if you don't know something for sure, please say so. I don't want to play in electron traffic because somebody just guessed at a solution. And second, if you disagree with somebody, don't call him names, okay? There's more than enough gratuitous meanness in the world right now without insulting people over stereo equipment. Thanks.
I have to agree with klh007 here. Grounding problems can be difficult and frustrating to find and cure. Using a balanced power unit can eliminate this problem. Yes, there is the expense of an additional component but the benefits are plausible. There are many balanced power units available including Equi=Tech, Furman, BPT (now out of business) and Torus Power. Research balanced power to understand the benefits. Here is a link that will help....
(I don't know if you specified it, but I couldn't find it -- does the hum vary with the volume control level, or is it there with the volume all the way down? -- I'm guessing the second, but just in case)
There is another way for hum to get in that is not a "ground loop" in the normal sense, and that is for the cabling to be picking up AC magnetic field from a nearby source (similar to a winding around a transformer core). Both preamp and amp can have a common ground connection, but current can be induced into the cable by the field. Does the hum change when you move the cables (lift them off the floor, or route them differently...). If so, you may be chasing the wrong problem.
Overheating conductors in walls is a major cause of house fires so you are correct but then you did prove my point. The grounding scheme in residential construction is designed to protect property not people it’s a well known fact and as I said you just backed that up.
No, I did not back that up. I said that **the breaker** protects against fires in the walls due to overheating conductors, not the grounding scheme. As I said in the last paragraph of my preceding post, "under most circumstances the safety ground conductor has no involvement in the fire protection provided by a breaker."
I also explained how the grounding scheme, specifically the safety ground connection, protects against electrical shock in the event that the AC "hot" wiring within an electrical device shorts to its metallic chassis (if it has a metallic chassis), by causing the breaker to trip before anyone has a chance to come in contact with the "hot" chassis. That is why 3-prong outlets and 3-prong power plugs (on devices that are not "double insulated"), which provide a safety ground connection, replaced 2-prong types (which don't provide a safety ground connection) many decades ago.
I agree, of course, with your statement that "GFCIs will react and kick in milliseconds not seconds and are designed to protect people." However your preceding post, to which I was responding, stated that...
If there is current on the chassis and someone touches it the breaker is probably not going kick in time to save someone. Only a GFCI which is designed to protect people may save someone from a shock or electrocution.
... which as I explained is not a correct statement.
The ground system in a home is not for people protection it is for fire protection. If there is current on the chassis and someone touches it the breaker is probably not going kick in time to save someone. Only a GFCI which is designed to protect people may save someone from a shock or electrocution.
No, that is not correct. A short between AC "hot" and the metal chassis of an audio component or any other electrical device having a 3-prong power plug is obviously very unlikely to materialize at the same instant someone touches the chassis. So the breaker will almost certainly have tripped some time prior to the chassis being touched, as a result of the excessive current that will be drawn by the short between AC "hot" and the safety ground conductor.
A GFCI can provide **additional** people protection under certain circumstances, such as in bathrooms or other areas where there is water.
And regarding fire protection, the main purpose of a breaker is to protect the AC wiring in the walls from overheating, as a result of an overload. In the event of an overload, the breaker will trip as a result of the excessive current passing through the "hot" conductor, which will normally be returned through the "neutral" conductor, not the safety ground conductor. So under most circumstances the safety ground conductor has no involvement in the fire protection provided by a breaker. That said, however, there are certain scenarios in which defeating the safety ground connection of an audio component could conceivably result in a fire hazard, as well as a shock hazard.
Can you tell me why PS Audio cords have removable ground pins?
I’m not familiar with their power cords. But I would guess that if those cords allow the AC safety ground connection to be defeated then the PS Audio components that they are presumably intended for use with (or if they are non-removable, that they can only be used with) have internal AC wiring that is "double-insulated" and is therefore very unlikely to ever develop a short to chassis. Assuming the chassis is metallic, that is. If the chassis on any of their components is non-metallic and as a result non-conductive, that would be an additional reason why defeating the safety ground would be a reasonable practice in those particular cases.
There are amplifiers sold with ground lift switches, so I think this is a common problem and amp manufacturers think it a safe solution.
As a point of information, the ground lift switches that are provided in some components do not isolate AC safety ground from the chassis of the component, as a three-to-two "cheater plug" would do. Rather, they isolate the component’s internal signal ground from the chassis, which does not result in the safety hazard that isolating AC safety ground from the chassis would result in.
Try temporarily running a wire from the preamp case to amp case. This assumes both cases are connected to their respective ground paths.
Could also be a problem with a cable or jack. Any oxidized jacks? Does every cable between the components cause hum? Test with only one connected at a time. If hum is only from one, try a different cable on that jack to jack path. Heck if stumped I might try reversing the cables, one at a time, to see what happens. That is mainly if the cables are directional.
If none of this makes any difference, then you know the problem is most likely internal to the preamp.
@edwyun I haven't received a response from Rowland, so that would actually be super-helpful if you'd be willing to check. (I'll holler at them if I don't hear by tomorrow.)
The thin trace is on the top side of the power board, in the corner where the ground ring connects to the AC receptacle two inches away. (Since the cover is on the bottom, you can't see the top side without unscrewing the board, but it's super-easy, just four hex bolts.) Here's a photo of the board and the ground I'm wondering about:
Thanks for the update. When I get a chance, I'll check my Capri to see if it is an issue as well. But, I don't have any ground hum (except for a little EMF hum from the phono input only at max gain).
I've been busy but have read through everything each of you contributed. I'm very grateful to everybody for taking the time to offer thoughts. Thank you.
Here's the update:
I used what time I had to reroute and reconfigure the two electrical circuits in the house per my last posting. My back is sore, my fingertips roughed up. And when I finally had everything put back together... Can you wait?! ... No change. I kinda expected that, being a pessimist at heart, but was still disappointed. Hey, at least I lowered the ground resistance to near zero in the system's circuit.
So I kept poking and think I have probably found the real culprit: the Rowland preamp.
I should have tried some of these things first, as they're simpler, but alas, we all learn by experience, yes?
Turns out that when I run my DAC straight into the amps, the hum is barely audible. (It's a Mac server, so I can control the volume through iTunes.) That also seems to eliminate that digital equipment as the cause per se.
But here's the salient clue, something I hadn't tried before: If I disconnect all source cables from the preamp, and then disconnect the preamp from the AC power, leaving the preamp and amp connected ... the hum remains. Yikes.
I opened the preamp and looked at the power board. There is a cap with one leg connected to the ground screw via a PCB trace, but the solder connection is hair-thin. I've contacted Rowland to ask if that trace is supposed to be stronger, which I'm capable of addressing myself. But if that's not it, I'm awaiting their response, which I assume will include sending the preamp to them.
The greatly reduced hum has also allowed me to identify a little RFI in one channel, but I'll take one thing at a time.
If this stimulates any thoughts, I'd be glad to read them. Otherwise, this feels more solid to me and I hope it's the beginning of the solution.
In my best system I run AG horns, my current Trios are something like 102 db sensitivity or even higher. They pick up tiny hums, noise, sometimes I think even insects walking around stealthily in my basement. I've run many amps, low and high power tubes and low and high power solid state, and always encounter what I call ground loop issues. Get out your cheaters and lift all the grounded power plugs, disconnect unused circuits throughout the house, etc, to no avail. Still the damn hum and noise. My cure, courtesy of Steve McCormack, now running SMc Audio. The music source is not the problem. Make a triangle from your pre-amp to both mono blocks, all three legs. Ground them to each other, all three legs. Unhook your sub if need be. Voila, hum is gone, as is any stray noise. Now, you would think the third leg is redundant. ie the Pre separately linked to each block, and thus the blocks have a hardwire ground to each other via the Pre. Well, I did that, two legs instead of three,rid myself of most hum and noise, yet still had some audible hum and noise. Connecting all three legs equals dead quiet, and perfect source music. Sound illogical? Too much work? Hey, it blueprints perfectly in the ground plane, and I use solid copper wire, like 14 or 16 gauge, doesn't need insulation. Simple really. Avoid 12 gauge solid, not malleable enough, and any stranded copper, not worth the fuss for grounding. I don't know how you feed music to your sub, but I'm sure you can hook in after you know the noise is gone. Good luck. Best regards, Joel
Consider trying an Equi=Core PC that is actually a Balanced Power device using a proprietary transformer to split the 120V into 2 out of phase 60V halves, and when they are recombined the non zero summed noise is drained to ground, lowering the noise floor dramatically. Tim Stinson of Luminous Audio couldn't get rid of a ground loop hum at the 2016 Capital Audiofest that was preventing Tim from using his Arion Phono Stage in a system, Sunil of CARE Audio loaned him an Equi=Core 300 and solved the hum instantly.It's worth giving Mark a call at Core Power Technologies.
If you are using inter-connects with arrows on them , the arrows must point to the Pre-Amp .......Most of the time people think they should point to the way the signal goes, which is wrong........The arrow points to the grounded end of the cable (which is only grounded on one end) This will cause this type of problem..........autospec
Disconnect any CATV hookup regardless, you may be surprised.
I fought a ground loop hum for a month or so, and ignored the CATV line because it was on a different circuit. Turned out to be the culprit anyway. Ground loops find a way.
This happens due to a different grounding point. I discovered this at my house also, but with DSS/DirectTV back in the early days. I had the dish and coax grounded outside right below the dish with a separate copper grounding rod, and the electrical service in the house was grounded 35 feet away, at the service entrance. I didn’t realize it at the time, but those two different grounding points are a difference in potential, as well as creating a 35 foot "loop" if the ground from the satellite were somehow introduced into the audio system (which is what was happening with the DirecTV receiver). When I unplugged the satellite coax, the humming went away.
While this doesn’t quite apply in the case of the OP’s question, it makes me wonder what the grounding situation is for the wiring in the house. If everything is grounded through the circuit breaker panel (which in turn is grounded to a single point in the house such as a water pipe, or outdoors to a stake in the ground), then it should be OK. But if somehow the newer wiring is grounded in a separate place, then that could cause a problem.
I have an odd hum issue in this house as well. My equipment is in an addition built in the mid 1980s, where the original part of the house was built in 1940. I found out that the ground wire isn’t connected in some of the outlets in the addition, so I have my own dilemma to attend to shortly...
bigaud brings up a good point. Try and isolate all the receptacles on that circuit and check/tighten all the connection at the receptacles and at the breaker (after turning it off of course). That would cost a little time.
Before running Romex, I would open the outlet box, the closest electrically to the incoming power, and check all the connections. Then follow the lines to boxes going back to the panel, or coming from the panel, and check those connections. Tighten or re-do when in doubt. if there is no separate ground wire, a poor conduit connection somewhere may be the cause.
I had one customer where the cable TV ground where the cable entered the house LOOKED proper but did not actually electrically contact the pipe it was on, and the system got a hum (though that may have been only when using TV. ) I fixed the connection so it actually grounded and the hum disappeared.
Another had a cable box and a modem in proximity, and I ran a wire from the cable box case to the outlet box (ground) to kill the hum.
A friend ran a wire between two of his components' chassis to kill a hum or noise.
Thanks to all of you, especially @toddverrone, @almarg, and @xti16, I think I have it figured out.
The original circuit feeds the two outlets at the system end of the room. I don’t think that was installed in 1936, but it’s in metal conduit, so it definitely isn’t too recent. Not surprisingly, one outlet box connects to the other, so any shortcomings in the circuit are shared.
Mais voilà. There is a four-gang outlet at the opposite end of the room that we added upon buying the house in 1998. (The room doubles as my office.) It’s Romex-fed, and I think it even has its own circuit. There’s some other stuff on it (most unfortunately a laser printer), but when I run a long extension cord from the system to the 1998 outlets, the hum is almost totally gone. At any rate, it’s acceptable.
From there isn’t not too hard for me to run some Romex about 20 feet and install a new outlet at the other end. Some day somebody is going to ask what the hell went on, but for now it should solve the mystery.
If anybody thinks I’m wrong, please let me know. Otherwise, for now, I think it will work.
Thanks again for all the time and advice. I’m truly grateful.
@pbraverman Yes that is what I was trying to say. The Voltage between neutral and ground means there is resistance in the wiring. But at less than 1V is not bad.
Edwyun 2-22-2017 There can be a combination or cumulative effect of issues.
+1. Specifically, it’s possible that there is nothing "wrong" with the AC wiring to the listening room, but it may have different characteristics than the more recent wiring to location 1, which in turn are bringing out an inherent susceptibility of the power amp/preamp combo to ground loop issues.
More specifically, see pages 31 to 35 of this paper, written by a renowned expert on such matters, in which he describes "what drives 99% of all ground loops." As you’ll see, Romex (which perhaps was used in the relatively recent wiring of location 1) is much less likely to bring out the susceptibility to ground loop issues that is inherent in some designs than wires randomly positioned in conduit (which perhaps was used in the older wiring to the listening room).
If that is what is occurring, and it seems like a reasonable bet at this point, a solution may be to have an electrician install new wiring to the listening room, using Romex. Alternatively, inserting a suitably chosen Jensen transformer between the preamp and each of the amps would probably resolve the problem, while also perhaps reducing other forms of noise, at a cost of around $300 plus some additional cabling.
Reports that have been provided here regarding the transparency of Jensen transformers have generally been very positive, although I can recall a couple of people who have provided comments that are a little bit mixed.
A suitable Jensen model would be the PI-RR, which would accept an RCA cable at its input and provide an RCA output, or the PI-XR, which would accept an XLR cable at its input and provide an RCA output. You would need two of them, one connected via a short RCA cable to the input of each amp. The cable from the preamp to the Jensen transformer could be whatever length is necessary. Here is a good supplier, although they can also be ordered directly from Jensen.
Also, although it is apparently unrelated to the problem I would still strongly advise that at some point soon you eliminate the XLR-to-RCA adapters, that are shorting the signal on pin 3 of the preamp’s XLR outputs to ground. If the sub does not provide XLR inputs you could either special order adapters from Cardas which leave pin 3 open, or have a cable supplier custom make an XLR to RCA cable which leaves pin 3 open, or purchase a Jensen PI2-XR transformer which would provide two channels of balanced to unbalanced conversion. Or you could use the preamp’s XLR outputs for the main signal path, connecting them to the amps via the Jensen PI-XR transformers, and connect RCA cables from the preamp to the sub.
@edwyun Acknowledged, and thanks. What I should have said is that there's a little bit of RFI that I can hear, and a LOT of hum that sounds like a ground loop. I'm trying to attack one thing at a time. (I'm not that bright!).
@toddverrone Got it. But wouldn't the acceptable performance in locations 1 and 2 seem to indicate it's not the entire electrical service?
Doesn't seem to be any harm in pulling the panel, shutting off the main breaker, and having a look tomorrow. I'll disconnect and reconnect the relevant breaker (#3) while I'm in there. If I don't reply further — well, you'll know I skipped the second step.
When I mentioned loose or dirty connection, I was thinking of the connections inside the panel. So the connection where neutral connects to the neutral bus, hot to the hot bus, ground to the ground bus. If you open the panel and shut off the main service breaker, you’ll be able to loosen then re-tighten the connections.
It does sound like a ground loop, though one that is related to the branch circuit it’s on. Which is weird.
@edwyun Thanks for the input. I'm pretty sure it's a ground loop, since lifting grounds does have some clear effect. There is the slightest trace of RFI if I put my ear an inch or two from the speaker. I'm not sure I can slay that, but I can tame it a bit with cable choice.
If you think my analysis is off, by all means say so — I'm not an expert here.
@xti16 Hey... I think I agree with what you're saying but I'm not understanding the first line.
Are you saying: "Since locations 1 and 2 don't have a problem, but location 3 DOES..." etc.?
If that's what you're suggesting, it makes sense to me. I've tried nearly everything else and the fact that the equipment works in some locations certainly suggests that the equipment isn't the problem. Just confirm that I've got it right above.
All of that said, what continues not to make sense is that the voltage potential in location 2 and 3 is the same (and too high), but only location 3 has the killer hum, where location 2 is basically okay (at least sonically).
Since location 1 does not have the problem but locations 2 & 3 are not tells me the problem is not with your equipment but with your wiring or something plugged into the wiring. So I would suggest either start unplugging devices/appliances etc and see if the hum goes away. If it doesn't I would suspect a corroded or loose connection in the wiring on that circuit.
Hi, folks. Sorry to be unresponsive; had some actual work to do there for a while. Thanks as always for the input.
Phase: All three circuits I checked are on the same phase — if I understand correctly — meaning all three are on the left half of the panel.
@toddverroneI think that answers your first question, yes? As to the dirt or loose contact: Are you talking about a contact at the breaker in the panel? The breaker has only one leg, doesn't it — is there a neutral or ground lead there? If you're talking about a problem at the outlets themselves, the problem is the same on two different outlets in my listening space so it seems unlikely that's it.
@gs5556 Yes I did, but thanks for the suggestion.
@almarg Yes, either amp behaves the same way with the other amp clear of the system.
An experiment I'd suggest at this point that might prove to be informative would be to see if either
Quicksilver amp produces hum when it and the preamp are connected and powered up as usual, but with the other Quicksilver amp disconnected from the preamp and unplugged from the AC.
If you look at your breaker panel, there will be a column of breakers on the right and one on the left. Each column is a different phase. So it could be a problem if you had an outlet in your room connected to a circuit coming from the left column and a different outlet on a circuit on the right side and then you connected your components to both of those outlets, willy nilly. The power sine waves are shifted relative to each other (180* I think) so that they don’t line up...
Have you checked the connections in the panel (if you’re knowledgeable enough to do this without killing yourself)? It seems it could be a loose/dirty neutral or ground within the service itself.
I second the idea that it would be possibly useful to know which phase the three different locations are on. Particularly if location 1&2 are on a different phase than 3.
"Location 1: Recent construction, new electrical service 2004. Wiring is correct. No hum at all. Neutral/ground voltage: 0.1VAC" This tells me the AC is a problem between the Rowland and the Quicksilvers. Question is what? The #2 location has minimal hum. It could be location 1 and 2 are on different phases. If so there may be something on the same phase as location #3 that's causing the hum but on a different breaker.
@swampwalker Good deductive powers, my friend, though the difference is pretty drastic and the sensitivity would have to be really, really high. With the Quicksilvers I can hear the hum from 15 feet. With the SS amp it's quiet as a tomb from 6 inches.
Others: I've searched online and wonder about grounding the chassis of the Quicksilvers to the chassis of the preamp. I understand that my lack of understanding may lead me to ask this question, and that may be the dumbest suggestion you've heard since breakfast (I mean since breakfast time, not the idea of breakfast). If so, feel free to put me straight.
This suggests some kind of issue between the Rowland preamp and the Quicksilvers, yes? It also suggests that the AC power by itself isn’t
really a problem. But whaddo I know? Any ideas?
pbraverman- I don't know nothing 'bout 'lectricity or circuit design ;-) but my powers of deduction say that, based on your posts of 11:55 and 2:30, it is possible/likely that the Quicksilvers either are more sensitive to a problem with the AC (in circuit 3) or there is an unusual aspect of the internal grounding of the Rowland and the Quickies that is incompatible.
Okay, here’s a little more info. (I work at home. You can see I’m getting a lot done today. LOL.)
I have a SS amp with balanced inputs as well. When I substitute it for the Quicksilvers, the hum disappears, even with the sub connected. This is true whether I connect the SS amp directly to the XLR outputs or to the RCA outputs via RCA-to-XLR cables.
This suggests some kind of issue between the Rowland preamp and the Quicksilvers, yes? It also suggests that the AC power by itself isn’t really a problem. But whaddo I know? Any ideas?
And to answer the obvious question: Yes, the Quicksilvers sound about a zillion times better, so keeping the SS amp instead isn’t really an option.
@xti16 Hell, sorry. That should be neutral/ground in #3 above. Anyway, it’s 124.5 in both spots. Also, the receptacle tester reports normal service in all three locations.
Oh, and @mcroth — thanks for the suggestion, but you're right, when the sub is totally unplugged the hum is diminished slightly, but still pretty audible from several feet. I appreciate your raising the idea!
Again, thanks to everybody for taking the time. Here are new data as of this morning:
@cleeds I never think of my video stuff as a separate system, but it obviously is. I ran the preamp through a Meridian 551 integrated amp and then to a pair of Totems. All but dead silent, so it doesn't seem to be a noise problem with the preamp itself.
@almarg I was so hopeful it was the XLR/RCA adaptors, as Al suggested (the easiest fix, after all). Alas, unplugging them changed nothing. While I was at it, I switched the amp runs from the RCAs to the XLR/adapter outputs. Again, no change.
@xti16 I did try lifting preamp ground only, with and without using the Hum-X on the preamp. Slight changes, nothing significant. I'm resisting the circuit-breaker dance for two reasons: first, see data below. Other circuits don't seem compromised; and, second, the breaker box is three stories down and while I'm in decent shape, I am no longer 25 years old. ;)
Okay, here are some more data.
Plugged the amp and preamp in two other parts of the house, using the same cabling each time. Here's what I found:
Location 1: Recent construction, new electrical service 2004. Wiring is correct. No hum at all. Neutral/ground voltage: 0.1VAC
Location 2: Original construction, 1936 wiring but service upgraded, probably 1990s. Not the same circuit as #3 below. Wiring is correct. Barely audible (acceptable) hum Neutral/ground voltage: 0.0VAC Hot/ground voltage: 0.8VAC Yes, those are right; I measured several times and re-checked wiring
Location 3: Listening room Wiring is correct Hummmmmmmmmmmming bird Farms, may we help you? Hot/ground voltage: 0.9VAC
I'm now wondering if it's something to do with the circuit that feeds the listening room — but, again, that's just logical speculation, blissfully free from the constraints of actual circuit knowledge.
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