ground loop?

Bill,

If your amps and preamps require earth connections, then effectively by using 3 to 2 pin plugs you are removing the earth connection to the equipment chassis. This earth is provided as an electrical safety feature, and is mandatory.

The fact that it's plugged into an earthed line conditioner makes no difference, as the equipment chassis is still not earthed.

If you can give me a run down of all of the equipment that is connected together, I'll see if I can come up with any suggestions.

Graeme

P.S. I've had a persistent earth loop problem myself for some time which I've finally solved. My main hi-fi speakers and associated pre and power amps are used as the front channels on my A/V system.

If I disconnected the analog connection from the TV, the ground loop hum was still present. If I disconnected the SP/DIF from the DVD player as well, the hum stopped. It turns out my cable TV box audio ground shares the same ground as the incoming coax cable (which is earthed by the cable company for safety reasons). Even having no direct audio from the cable box still caused hum, beacause the SCART leads on the DVD and cable decoder have a common ground which is shared by the DVD's SP/DIF and this was ground looping via the Dolby digital processor to the amps. The solution was to switch the DVD to TOSLINK, and I was going to put audio transformers in the analog outputs from the cable box, but our cable provider is now doing new TV Drive boxes which have TOSLINK digital output. Now all of my music stuff is connected by RCA phonos, and all of the video sound stuff is connected via optical digital. No more hum!!!
 
Thanks very much...perhaps I don't even have a ground loop but I am hearing a hummmmm through my Klipschorns (slight) which may just be because the speakers are so efficient...but many seem to think it was ground loop so...that's why I posted...
2 Tube Amps...3 prong plugs
1 Tube Pre-amp...3 prong plug
1 CD player...2 prong plug...
All into a Panamax MAX5100 power conditioner with a 3 prong plug into a wall outlet.
I have changed around ICs as well...Nordost Black Knight, RCA branded Didgital with gold ends...home made (not by me, appears to be mic cord) with gold end connections

My continuity tester says all plugs test fine...for proper grounding and wiring...
thanks
Bill
 
silversport said:
Thanks very much...perhaps I don't even have a ground loop but I am hearing a hummmmm through my Klipschorns (slight) which may just be because the speakers are so efficient...but many seem to think it was ground loop so...that's why I posted...
2 Tube Amps...3 prong plugs
1 Tube Pre-amp...3 prong plug
1 CD player...2 prong plug...
All into a Panamax MAX5100 power conditioner with a 3 prong plug into a wall outlet.
I have changed around ICs as well...Nordost Black Knight, RCA branded Didgital with gold ends...home made (not by me, appears to be mic cord) with gold end connections

My continuity tester says all plugs test fine...for proper grounding and wiring...
thanks
Bill

You have some nice equipment. Why play around with ten cent cheater plugs that eliminate any earth ground. See my above suggestion. In fact, if you want to save money try wiring all of your components chassis' to the preamp ground.
 
Bill,

Your setup is considerably less complicated than mine, so if it's ground loop, it should be fairly straight forward to check out. A very quiet 60 Hz hum is not unusual on equipment. If it's ground loop, when you wind the volume up with no signal applied, you'll hear it plenty.

Check all of your RCA connectors are a snug fit. Check the home made ones are soldered OK inside the plugs with no stray strands. Make sure your mains cables and interconnects are kept well apart and if they have to cross, make sure they cross at 90º to each other to minimise interaction.

With your equipment switched off, check for earth continuity with a multimeter between the RCA grounds and the chassis of your amps and preamps. Some equipment has the chassis earth connected to the signal ground. I don't like this approach because it's great at causing ground loops.

If you find the signal grounds are connected to earth, you could try bonding all the chassis together with additional earth leads. The other option if you're comfortable with modding is to open the amps up and separate the signal and safety grounds.

Graeme
 
Graeme and Tullman,
thanks...I give those a try...perhaps this IS just the normal noise from the equipment as it never gets any louder, volume change or not...thanks...I hear it with everything hooked up and on as well as when everything but the amps are off (however, they are still connected with ICs)
Thanks,
Bill
 
...the only time I get any increase in the hummmmm is when I change from the RCA branded ICs to the Nordost Black Knights...and it is only a very slight increase...'course hating to hear ANY hummmmm, I switch back to the RCA branded digital ICs...
Bill
 
Don't know if any of your gear has 3-prong plugs, but if so, get yourself down to the local hardware store and flip guy behind the counter a quarter for a "ground-lift adaptor."

You've seen 'em before - it's those little plugs that take a 3-prong and turn it into a 2-prong.

On the way home you can stop and get some gingham for the wife and rock candy for the kids.

This has worked for me every time with no ill effects.

:D
 
Last edited:
slow_jazz said:
i was having trouble with humming thru the receiver when using the dvd player hooked up to the t.v. and listening to the sound thru the receiver.

i purchased this and it solved the problem.

http://shop.vendio.com/stanh/item/576836496/index.html


As you see here, ground-loops are pernicious little beasties. The ideal power setup will have a common ground point, usually in the main circuit breaker box, where all the grounds (green wires in USA) are connected together and a single, heavy copper wire goes outside to an even heavier copper rod which is driven into the earth. As long as this is the ONLY true earth ground in the whole system you shouldn't have ground loops. Unfortunately, back here in the real world, things get complicated. As someone noted earlier, the cable company will do their own earth ground, and so does the phone company, and some equipment manufacturers tie their signal ground to the power ground. Anytime there is a different ground point you will get ground currents, which to an amplifier looks like a signal (60 hz.) The long cable device (RG-59) is known as a hum-bucking coil, a sometimes useful tool. The Ground Zero device attempts to get everything back to a single grounding point, representing the ground reference. If you look inside the circuit breaker panel (without touching anything!) you will see that is how it's designed, to be THE reference point for the whole circuit, or building. And I don't think the whole box costs as much as the Ground Zero unit does, even with all the circuit breakers. But bonding all your chassis together and verfying the integrity of all your signal wiring will go a long way toward cleaning it up. I still have problems from time to time on my systems, too. It's basically hunt and peck until you find the cause. And, yes, it may very well give you recordings with a hum in the background, so it's worth finding the cause.

Good luck, and good hunting. :thmbsp:
 
maybe!?!

try a 3 into 2 plug adapter - at each component, one at a time. a ground loop starts when neutral and earth ground get tied together where they shouldn't. they should only be tied in your main service entrance panel. anywhere else will manifest in a potential difference and allow current. don't confuse "common" and "ground".
 
I cured a terrible ground loop hum thanks to the single ground principle

VQLT,

I had a terrible ground loop hum in my office system: Revox B160 / Cambridge Audio 640C> Audio Research LS3 > D130> Infinity Primus 360, and I was also using a Yamaha S90 synthesizer through the computer soundcard (M-Audio 2496).

This produced a strong hum in the speakers and if I wanted to eliminate this sound from regular FM or CD listening, I had to remove the interconnects everytime from the LS3, and there was still a noticeable residual hum.

This hum drove me bonkers trying to sort it, and I was ready to throw out the whole thing and only listen to cigar box banjo when,...

In researching this problem, it seems it's the difference in ground potential of all the various components that are tied together at the power source that caused the ground loop and hum. (-And a reason to be careful when mixing consumer and pro gear).

Knowing the multiple grounds to be the problem the cure, is relatively simple- have all related components go to the same ground. I bought a big- it's 43 lbs. -12 amp Oneac hospital power conditioner. The key to this is that the Oneac (and Powervar) are isolation transformer conditioners so all the power is ouput from a BIG transformer- hence the 43 lb- that is taking the power from the panel and "reworking" it and the ground is then common back to the panel. There is also substantial surge protection and RF filtering This model Oneac has 5 outlets- four 15 amp plugs and one 15A twist lock- not enough plugs. I bought a 3-outlet contractor's 10 gauge power distribution cord- $6 at Fry's!, shortened it to 1' and added a nice Wattgate twist lock plug, giving me a total of 7 outlets. I then plugged everything- S90, LS3, tuner, CDP, and phone /answering machine into the Oneac. plugged the "second string" components- phone, DLS modem, and computer into the distribution cord and the main ones- preamp, CDP, S90, and tuner directly. I should explain adding the phone to this connection. Anything connected to an external cable system: telephone, DLS or TV cable has it own ground- and remember it's the multiple, different potential ground potentials causing the trouble. The Oneac has an outboard telephone line ground isolator and since the computer has a DSL- I needed isolate the DSL and FAX telephone line from it's own competing ground. I'll wager that a lot of people who have their computers tied to their audio systems miss this contributuon to their hum. I tied the phone and DSL lines to that isolator which in turn connects to a knurded-knob post on the Oneac. Btw, these Oneac phone isolators are often seen on Ebay for $15 to $20. Importantly, the D130 power amplifier- which draws up to 900W- is not happy running on a conditioner so it's plug occupies the other spot of the duplex outlet and of course, the ground of the two outlets is the same.

Results: black background- well 95%.

Btw, I'd been using a 6.5 Amp Powervar before the Oneac and didn't realise how constrained the sound was, though I believed it had considerable headroom. The 12 amp Oneac literally transformed the sound- more open, transparent, better imaging- sustantial, immediately noticeable improvement all round. I recently bought a 10A Powervar to replace the 6.5 and I recommend anyone taking advantage of the amazing bargain big isolation transformer power conditioners (the Oneac was $50 and cost $50 to ship) to buy 10 Amp or greater. The 6.5 will become the TV/bedroom system surge surpressor- in 2004, when remodelling I had my beloved 1990 Sony 27" and a Pioneer DVD go up in smoke after a surge.

I've noticed that people are catching on to these conditioners as bargains- extremely high quality and effective gear- that were expensive new-the Oneac listed at $1400 three years ago- and I notice the prices of used rising. I feel the Oneac is somewhat higher quality than Powervar, but they're both impressive.

In my future home, I'll run dedicated audio circuits in large gauge wire in conduit to hospital outlets and then through to an isolation conditoner.

Cheers,

Bambi B
 
Really, Just wire to the ground on your preamp all of the components in your system. It really works! Just loosen a screw on the chassis of you components attach a wire and run it to the preamp.
 
.dh. said:
Don't know if any of your gear has 3-prong plugs, but if so, get yourself down to the local hardware store and flip guy behind the counter a quarter for a "ground-lift adaptor."

You've seen 'em before - it's those little plugs that take a 3-prong and turn it into a 2-prong.

On the way home you can stop and get some gingham for the wife and rock candy for the kids.

This has worked for me every time with no ill effects.

:D

Out of my 25 components, 2 were giving me trouble.
I took your advise and put on cheaters.

Problem solved!!!:thmbsp:

Thank you so much, Steve
 
When i lived in barrie ontario Rodgers Cable used to give off a terrible hum loud too. I solved most of this problem by buying a 3 dollar ground clamp and running wire from my system the the cold water pipe in the house. Its where your panel is grounded usually. I still had a slight hum when the sound for the cable tv was hooked up to the stereo. No where near what it was though.
 
I've got a problem with hum when just the amp and pre-amp are plugged in. With just that amp plugged in, no problem. As soon as I plug in the pre, even with it off and nothing hooked to it, I get a hum from the speakers? How would I fix this? Tried running a wire from chasis to chasis, didn't help. different sockets, didnt help. my pl 4000 didnt have a problem, but thats in for service so Im using my new to me pl 2000 and have the hum. Any ideas?
 
I havent read any of the posts in this thread but I thought I would mention I picked up a ground loop isolator from radioshack today for 20 bucks for use between my computer and stereo and it works perfectly. I cannot notice any difference in sound quality, Besides the fact the annoying hum and buzz is now gone completely. I probably would not use this particular unit on anything I did any critical listening to but for something like this is works great.

Catalog number 270-054

http://www.radioshack.com/product/index.jsp?productId=2062214&cp
 
I havent read any of the posts in this thread but I thought I would mention I picked up a ground loop isolator from radioshack today for 20 bucks for use between my computer and stereo and it works perfectly. I cannot notice any difference in sound quality, Besides the fact the annoying hum and buzz is now gone completely. I probably would not use this particular unit on anything I did any critical listening to but for something like this is works great.

Catalog number 270-054

http://www.radioshack.com/product/index.jsp?productId=2062214&cp

That's what I did, between the computer and the preamp.
 
Ground Loops come in so many flavors there is no one fix good for all solution. I saw Bill Whitlock (Jensen Transformers) gave a great presentation on grounding, ground loops and the like a few years ago. Bill's :ntwrthy:"the man" on this stuff and debunks a lot of the idea's about balanced power etc. Here's a link to his White Paper: <http://www.jensen-transformers.com/an/an004.pdf>

After absorbing this, ground loop troubleshooting became a lot easier.
 
I have a pair of interconnects that are made up with the shielding connected only at one end for use on my CATV box, which operates on a different ground plane than the house-grounded audio equipment.

The hum is created when the 60 hz ac signal travels along the shield. Break that connection and you have eliminated the hum. Any interfearance that needs to be earthed by the shield can travel to ground at one end of the cable. It's best that the grounded end of the interconnect is connected to a component with a 3 prong plug.

This is the way shielded signal cable is handled in industrial enviroments - always- because long runs almost always travel between electrical services with different ground planes.

I wonder what advantage comes from having both ends of the shield soldered to the RCA plug in the first place? It seems like a unnecessary and troublesome protocall.
 
Back
Top Bottom