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
bigaud
8 posts
 
If this helps it will be less work.

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.

xti16
1,525 posts
 
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.
shoresaudio's avatar
shoresaudio
20 posts
 
@jmcgrogan2 wrote:
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...
autospec
451 posts
 
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
klh007
616 posts
 
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.
More to discover