ground loop?

My new-to-me Lux 1050 receiver has a hum through the speakers that sounds like 60 hz - when I raise the volume with no input the hum gets louder - am I hearing a ground loop-type problem or am I listening to an amp problem?

For another month I am living in an apartment then we are moving to our house so I am not too worried about solving a ground loop here, but I am very concerned that the amp might need servicing.

The bias readings are .006V and .003V on the channels, which I understand are very good.

Any help on this would be greatly appreciated!
 
It's very simple. Use ground cheaters on all but youtr amp and then run ground wires from the amp to each component's chassis. that way everything is still grounded for safety and there should be no ground loop.
 
Actually, couldn't completely kill the hum, sent the receiver to a guru here and after some difficulty, he found a bad ground in the power supply. I pick it up tonight!
 
Hey I have seen many of the great answers on here and a lot of them have to do with purchasing a Product of some sort..

I would suggest in this economy you find an Electrician (seem to be cheap now a-days) and have him Lift ground for you on the Outlets you might use (would not suggestion all of them). I would also suggest you use a different Color Outlet Cover.

I actually had this done in my new house for my home Studio (10-15 outlets) and it cost me around $400...

Just another thought...
 
Low cycle hum......two things make sure your rca jack cords are twisted together..
like a huge twisted pair. You dont always need to plug in tha same outlet just turn the
plug around and reinsert.
 
You might need something called a Audio System Gound Loop Isolator. It is part number 270 054. Available at Radio Shack for about $17.00USD. It took me three years to solve a crackling sound I was getting when I attached my laptop for internet radio listening to my home system. Then, while surfing Youtube, I came across a video that showed the Ground Loops Isolator. When I installed the part, it worked great and I was extemely happy to have my internet radio programs working on my home system. Scottsmrnyc
 
Could be the terrible CABLE HUMMER,

I've found over the last 25 years I've had at least 6 major grounding problems. All were similar in that they had a flat volume level regardless of actual volume on attenuator. They ranged from 50 db to maybe 70 db enough to scare the crap out of me. ALL turned out to be cable vision induced . Only happened when I wanted to hook up the stereo to hear tv or cable radio stations. Only one time it got fixed the cable guy grabed a 3 ft metal ground spike hammered it into the ground and grounded the cable directly there.
They wont do that any more as their system is now totally self relient grounding is done at the post as they don't want hydro to taint their signal as apperantly it can case them lots of grief. So when I wish to watch a movie I need to undo cable line using a good quickconnect.

Hopes this helps a little

All the best Les
 
I had a high-end pre-amp that sounded bad. First time I had a grounded pre-amp. Lifted the ground inside the pre-amp and everything came into focus. Best to only have one grounded component and let the interconnects ground everything to the grounded component. Ground loops that go through interconnects and grounds in the AC power connections can be a major mess.

Remove interconnects and power things up. Use a DVM and check AC volts between the grounded component and the others. Rotate power plugs [if possible] and look for smaller voltages.
 
***Edited to remove malware content in quoted post. Not clyde's action***

So all eleven of your posts are nothing but that sutpid laughing icon. What's up with that?
 
My computer causes my ground hum. I have the audio from a Computer, DVD player, VCR, and turntable all hooked up to the same receiver. I guess for now I'll try doing the wire string from computer chasis to preamp ground and see how that works.
 
if I have a ground loop and I am using a Panamax Max5100 line conditioner that has spike protection and all...could I perhaps plug my amps and preamp (all 3 prong plugs) into it using cheaters (3 into 2 plugs)??? I understand I WOULD be losing my ground for these individual pieces BUT if my Panamax is grounded into the wall outlet (Panamax shows fine with the ground and the wall outlet lights up on my tester as properly wired and grounded) would I then have 1 ground for all my pieces and avoid the ground loop???
Sorry, I have done so much searching and reading on ground loops that this seems far too easy (so it MUST be wrong ;) but I just had this thought perhaps I was overthinking this...It couldn't be THAT easy a fix, could it???
Bill

Never ever defeat the ground with a cheater. You may create a potentially lethal situation. Get a simple grounded multiple box and plug each piece of gear one at a time into the box to see when the hum occurs. if it doesn't then the Panamax is defective or there is something overlooked in it's installation. if it occurs with the mult box then you know which componant is the culprit
 
OK...I just did the thing where you unplug each component in the system to see what is creating the ground loop hum thru my speakers. In my case, it is my Rotel-RB-1080 amp. So I now have the ground adapter that goes from 3 prong to 2 prong plugged between the amp plug and my powerstrip. Now is this OK to do, my power strip is plugged into a grounded outlet.
If this is not too safe, then what can I do to fix this in a safer way? I plan on trying to bi-amp when my other equipment comes in with an identical Rotel amp.

Thanks!
 
OK...I just did the thing where you unplug each component in the system to see what is creating the ground loop hum thru my speakers. In my case, it is my Rotel-RB-1080 amp. So I now have the ground adapter that goes from 3 prong to 2 prong plugged between the amp plug and my powerstrip. Now is this OK to do, my power strip is plugged into a grounded outlet.
If this is not too safe, then what can I do to fix this in a safer way? I plan on trying to bi-amp when my other equipment comes in with an identical Rotel amp.

Thanks!

I may not be the amp. It may be that the ground loop is manifesting itself through the amp as it has a path to ground through the amps ground pin. Does the him go away when you disconnect the preamp from the Rotel? If yes, then reconnect the pre to the amp with nothing else plugged into the preamps inputs and nothing other than the preamp and amp plugged in to AC line. If no hum, then plug each front end piece into the pre one at a time both with the interconnects and AC line. One more question. Are all pieces of gear plugged into the same mult strip? Good luck
 
Yes, all components are plugged into the same power strip. When I unplugged the preamp from the amp, the buzz was still there. I have the adapter in there now and no buzz...
 
Yes, all components are plugged into the same power strip. When I unplugged the preamp from the amp, the buzz was still there. I have the adapter in there now and no buzz...

If all that's plugged in the wall is the Rotel poweramp which is connected to the speakers and no other components are plugged into the poweramp, powerstrip or wall receptacle then a few more possibilities exist.
1.The AC receptacle in the wall, or the powerstrip is neutral/hot reversed. There is a tester that has 3 lights that can be red or green,that Used to be sold at radio shack but I'm sure you can find it somewhere. Get one, check the outlets and strip for correct polarity and ground. Yes AC does have a polarity so to speak.
2.The AC receptacle in the wall does not have a good ground connected to the third pin. It's either not there, loose, or not making it back to bonded ground due to old wiring, a splice or miswired. I have also found that those $3-10 multiple AC strips have horrible grounds. Sometimes just a small tab that doesn't make a connection good enough to ground the higher current of audio amps. If the ground is tested good in the wall box, then plug the amp right into the wall and see if the hum disappears.
3. There might be a breakdown in the Rotels primary transformers winding, or the Rotel may be hot/ neutral reversed (especially if you bought it second hand from a tweaker, ) or you're a part time tweaker who screwed up something. This whole no.3 is the least likely so fix and check everything in no.'s 1&2 before going to 3. Good Luck. When you eventually get it right, there is nothing as satisfying as the audio from a noise free system.
 
If all that's plugged in the wall is the Rotel poweramp which is connected to the speakers and no other components are plugged into the poweramp, powerstrip or wall receptacle then a few more possibilities exist.
1.The AC receptacle in the wall, or the powerstrip is neutral/hot reversed. There is a tester that has 3 lights that can be red or green,that Used to be sold at radio shack but I'm sure you can find it somewhere. Get one, check the outlets and strip for correct polarity and ground. Yes AC does have a polarity so to speak.
2.The AC receptacle in the wall does not have a good ground connected to the third pin. It's either not there, loose, or not making it back to bonded ground due to old wiring, a splice or miswired. I have also found that those $3-10 multiple AC strips have horrible grounds. Sometimes just a small tab that doesn't make a connection good enough to ground the higher current of audio amps. If the ground is tested good in the wall box, then plug the amp right into the wall and see if the hum disappears.
3. There might be a breakdown in the Rotels primary transformers winding, or the Rotel may be hot/ neutral reversed (especially if you bought it second hand from a tweaker, ) or you're a part time tweaker who screwed up something. This whole no.3 is the least likely so fix and check everything in no.'s 1&2 before going to 3. Good Luck. When you eventually get it right, there is nothing as satisfying as the audio from a noise free system.


Well, I tested the outlet first time, with that 3 light tester and it tests perfect. So the ground has to be connected OK in the outlet. I'm not using the sub $10 powerstrip, I'm using almost a $100 audio/video powerstrip with lightning protection. I'm in the process of bi-amping, and it's not working out for some reason, so I'm for now using the newer Rotel amp, and it does the same thing. I think it's in the Rotel transformers. I bought both Rotels brand new and I don't tinker with the insides. Only thing I have done is replace the fuses before, and now again. So I guess using the three to two prong adapter is the best solution as it alleviates the hum/buzz sound.
 
Low cycle hum......two things make sure your rca jack cords are twisted together..
like a huge twisted pair. You dont always need to plug in tha same outlet just turn the
plug around and reinsert.

How do you turn the plug around with polarized plugs in polarized receptacles?
 
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!!!


I had the same problem with a ground loop between my house ground and the cable ground. I put a 3 to 2 prong adapter on my home-make amplifier and the hum was gone. The cable box is now the sole ground in the system (through the coax cable). The rule of thumb here is to allow no more than one external ground. I have never seen any commercial HiFi components using the ground prong in the power plug. Components are usually designed to "float" with respect to the mains.

If the hum persist but goes away when you unhook the cable line, there's a trick to isolate the cable box from the cable ground. Take two balun transformers (the adapter people used to use to hook cable up to old TVs that took twinlead) and connect the twin lead outputs of one to the other. Now you have a 1:1 RF transformer that breaks the ground loop. I would only try this as a last resort. Now that cable is a two-way digital system, the baluns might mess up your cable reception.

Bobby D.
 
Last edited:
Back
Top Bottom