1. Home
  2. tech-talk
  3. 128497-73725

Insane ground loop; anybody wanna try?

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.

Relevant equipment:
Rowland Capri preamp
Quicksilver Silver 60 mono amps (EL34)
Sunfire True Sub

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.
pbraverman
almarg's avatar
almarg
8,673 posts
 
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.

Regards,
-- Al


jaf36's avatar
jaf36
30 posts
 
I don't want to pirate this poor guys thread so I'm out after this comment. 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. GFCIs will react and kick in milliseconds not seconds and are designed to protect people. Do some homework you'll find that all of this is true. 
almarg's avatar
almarg
8,673 posts
 
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.

Regards,
-- Al


jea48
2,944 posts
 
jaf36  17 posts                                                                 03-14-2017 1:22pm

Can you tell me why PS Audio cords have removable ground pins?
Its’ removal is for testing purposes only. It can be temporarily removed to see if it will break a ground loop that may be causing a ground loop hum.

http://www.psaudio.com/forum/need-help-ask-the-psa-expert/removing-ground-pin-on-ac-12-power-cord/

Paul McGowan
PS Expert
Forum Posts: 4661 Member Since:
July 8, 2013

When you do this you are breaking a ground loop that is causing the hum. There are other ways to solve this other than removing the ground pin, but it will take some experimenting and, in some cases, only breaking the ground loop like you are doing works. Hopefully you can experiment with different grounding to get the same results.

Is it dangerous? Well, officially yes. What it means is the Esoteric hasn’t any firm safety ground except through the other connected equipment. Should a wire with AC power get lose inside the Esoteric and touch the chassis you might run the risk of electrocution. Unlikely, but that is the danger.



Co-founder and CEO of PS Audio.decades.


.
jea48
2,944 posts
 

.
.
jaf36      17 posts                                                         03-14-2017 2:57pm

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.

Like Al, (almarg), said you are wrong.

It is for protection of life from electrical shock or electrocution. The equipment ground places the metal cabinet/enclosure of the piece of equipment at the same ground potential as the main electrical service’s grounding system. Any grounded object within the premises is supposed to all be at the same ground plane potential.

If the metal case/enclosure of a piece of equipment is properly grounded any ground fault potential that comes in contact with the enclosure will pass the current through the safety equipment grounding conductor back to the earth connected service neutral conductor. If the ground fault current, plus equipment load, is greater than the breaker handle rating the breaker will trip open breaking the ground fault circuit. If the ground fault has a high series resistance good chance the breaker will not trip open.
The breaker sees the ground fault current as just part of the total connected load.
If the piece of equipment has a safety fuse the fuse should blow first.

(That is if the AC polarity is correct at the wall receptacle and the Hot conductor is connected to the line side of the fuse. If the AC polarity is reversed then the neutral will be connected to the line side of the fuse.) In any event IF a ground fault circuit is provided the current will travel back on the equipment grounding conductor to the earth grounded service neutral conductor. At no time is the enclosure/chassis HOT with respect to ground.

IF the enclosure of the equipment is properly grounded the enclosure is at ground potential and should never have any difference of potential to any other earth grounded object.

.
More to discover