[tanbark813]

At home, in my office, I have my computer connected to a stereo receiver with two speakers hooked up. The computer is connected to the receiver from the sound card via a cable that has 1/8" stereo jack on one end and two (left and right) RCA jacks at the other end.

Recently, because of a party, I wanted to hook up the receiver in my living room to the computer as well to have the same music playing in both rooms. That receiver is a little nicer than my office receiver but none of the equipment is bada$$. The living room receiver also has two speakers hooked up.

To do this, I connected two 6" RCA Y cables to the end of the cable coming out of the computer. Then, with the help of some male-male, female-female couplers as needed, I ran 2 20' RCA cables coupled together from the end of the cable coming out of the computer to the living room receiver.

I ended up getting a mild, but noticeable, buzzing out of both receivers/speakers. I checked and rechecked the connections but everything seemed fine. I finally isolated (sort of) the problem to the living room receiver or at least that 40' of cable. When the RCA cable to the living room receiver was disconnected, there was no buzzing in the office receiver/speakers. But when I hooked up the living room RCA cable, I got buzzing out of both receivers/speakers.

The buzzing was there whether music was playing or not. Also, adjusting the volume on the computer didn't affect the buzzing at all. Adjusting the volume on either receiver did affect the buzzing in each receiver/speakers, respectively.

To get around it, I finally turned the volume up high on the computer and down on the receivers to get the same overall music volume with less buzzing. That basically worked. However:

Is there any way to eliminate the buzzing altogether?

Am I trying to get too much out of the computer sound card?

My friend suggested that but I thought it would be fine since the signal was going to be amplified by each receiver. I could be wrong as I'm no sound equipment expert.

 

[bfahle]

Sounds like a ground loop, because you now have two grounds (one in each receiver). One of these should do the trick:
Scosche Eso34 Ground Loop Isolator

 

[tanbark813]

Sounds like a ground loop, because you now have two grounds (one in each receiver). One of these should do the trick:
Scosche Eso34 Ground Loop Isolator

I've never heard of one of those before but that sounds like it might work. Would I connect it basically between the Y cable and the RCA cable going to the living room speaker? Or would it be at the end of the cable coming from the computer (before the two Y cables)?

 

[hakukani]

This is why sound guys are also called 'humheads', because we often have to chase down ground loops like you're experiencing.

The buzzing could be caused by several things.

1) you're using a headphone out instead of a line out from your computer card, and the headphone amp is humming--not likely here.
2)There's a ground loop because the computer and the far receiver's mains (AC) are at a different potential (different ground).
3)There's hum/buzz being picked up by your 40' run of unbalanced RCA-type cable

2 can be solved in one of three ways. Make sure that the two AC plugs are at the same potential--that is, plug them into the same mains circuit. You can also 'lift' the ground on one of them--probably the far receiver--however it is not recommended for safety reasons. You could use a transformer in between the far receiver and the rest of the system, thereby isolating it. You could also use a mixer in between to isolate the two systems.

3 could be solved by running balanced cables for the 40 feet before using an adaptor to go to RCA, making the unbalanced run much shorter.

Of course, I could be totally wrong, and the cotton pickin' thing could hum away anyway---I've had that happen, too....

edit: I see that bfalhe has found a transformer for you while I was typing.

 

[tanbark813]

This is why sound guys are also called 'humheads', because we often have to chase down ground loops like you're experiencing.

The buzzing could be caused by several things.

1) you're using a headphone out instead of a line out from your computer card, and the headphone amp is humming--not likely here.
2)There's a ground loop because the computer and the far receiver's mains (AC) are at a different potential (different ground).
3)There's hum/buzz being picked up by your 40' run of unbalanced RCA-type cable

2 can be solved in one of three ways. Make sure that the two AC plugs are at the same potential--that is, plug them into the same mains circuit. You can also 'lift' the ground on one of them--probably the far receiver--however it is not recommended for safety reasons. You could use a transformer in between the far receiver and the rest of the system, thereby isolating it. You could also use a mixer in between to isolate the two systems.

3 could be solved by running balanced cables for the 40 feet before using an adaptor to go to RCA, making the unbalanced run much shorter.

Of course, I could be totally wrong, and the cotton pickin' thing could hum away anyway---I've had that happen, too....

edit: I see that bfalhe has found a transformer for you while I was typing.

Hopefully bfahle is right because this sounds complicated. Thanks, though.

After reading the instructions here:

http://www.ramelectronics.net/manufacturers/xitel/ground-loop-isolator-gli1s1/prodGLI1S1.html#

Would I actually need two of these? One for each receiver?

 

[JCBigler]

My money is on the long unbalanced run of the RCA cable. 40 feet is really about four times the distance that I like to run unbalanced cable.

Hopefully both of the AC outlets that your equipment is plugged into are grounded. If the house was wired properly in the first place, then they should both be connected to a common ground, usually a thick copper pole rammed about eight feet into the ground under your house, but it could also be a cold water pipe.

Does the power circuit test good when you plug one of these into it? They can be bought at Home Depot for about $4 or $5.

 

[tanbark813]

My money is on the long unbalanced run of the RCA cable. 40 feet is really about four times the distance that I like to run unbalanced cable.

Hopefully both of the AC outlets that your equipment is plugged into are grounded. If the house was wired properly in the first place, then they should both be connected to a common ground, usually a thick copper pole rammed about eight feet into the ground under your house, but it could also be a cold water pipe.

I'm not sure if it matters but it's an apartment, not a house. The "office" is the second bedroom in a two bedroom place. There are 16 total apartments in the building.

Does the power circuit test good when you plug one of these into it? They can be bought at Home Depot for about $4 or $5.

No idea. I may have to pick one of those bad boys up.

 

[JCBigler]

I'm not sure if it matters but it's an apartment, not a house. The "office" is the second bedroom in a two bedroom place. There are 16 total apartments in the building.

The main factor is the quality of the wiring installation. If it's done right then it doesn't matter if it's an apartment or a house. However, the fact that there are 15 other units in your building means that they may all be sharing a ground (and possibly, though hopefully not, a common neutral). If someone else in your building has shorted out their ground or is running something that puts noise into the AC distribution, then that can cause problems too. Apartment aren't inherently more prone to noise, just harder to troubleshoot.

 

[ultasax]

If as you stated the hum is audible even without music, then it is probably
a 60Hz ground fault or loop as has been suggested. So you might try using a "cheater" male to female A/C Plug. This is simply a typical 3 prong plug with the ground pin omited and a 3 hole female receptical on the the reverse side. You plug your equipment into this device and in doing so, cheat the ground, They are not UL approved but most music equipment stores keep a few around.

The other possibility is the 40 foot run of small diameter cable acting as an antenna and picking up and broadcasting A/C dirt. If this run cannot be balanced due to the probable absence of XLR connectors, it should at least be shielded cable so as to resist such interference.

Good luck with this, it sure can be annoying.

 

[hakukani]

I'm not sure if it matters but it's an apartment, not a house. The "office" is the second bedroom in a two bedroom place. There are 16 total apartments in the building.

The main factor is the quality of the wiring installation. If it's done right then it doesn't matter if it's an apartment or a house. However, the fact that there are 15 other units in your building means that they may all be sharing a ground (and possibly, though hopefully not, a common neutral). If someone else in your building has shorted out their ground or is running something that puts noise into the AC distribution, then that can cause problems too. Apartment aren't inherently more prone to noise, just harder to troubleshoot.

It depends on the age of your apartment or its location. My house was built in 1964, and had only a 60 amp service running to it, and no ground. When we remodeled, the first thing I had the 'electrician' do was to put in a solid earth ground and a 200 amp service. Now I can run my water heater and my dryer at the same time, without fear of getting electrocuted or tripping a breaker.

 

[tanbark813]

If as you stated the hum is audible even without music, then it is probably
a 60Hz ground fault or loop as has been suggested. So you might try using a "cheater" male to female A/C Plug. This is simply a typical 3 prong plug with the ground pin omited and a 3 hole female receptical on the the reverse side. You plug your equipment into this device and in doing so, cheat the ground, They are not UL approved but most music equipment stores keep a few around.

How risky is that? It wouldn't be a big loss if my stereo equipment got zapped but my computer is somewhat expensive.

 

[tanbark813]

It depends on the age of your apartment or its location. My house was built in 1964, and had only a 60 amp service running to it, and no ground. When we remodeled, the first thing I had the 'electrician' do was to put in a solid earth ground and a 200 amp service. Now I can run my water heater and my dryer at the same time, without fear of getting electrocuted or tripping a breaker.

I don't know exactly how old but I know the building has been around since at least the 70's.

 

[JCBigler]

If as you stated the hum is audible even without music, then it is probably
a 60Hz ground fault or loop as has been suggested. So you might try using a "cheater" male to female A/C Plug. This is simply a typical 3 prong plug with the ground pin omited and a 3 hole female receptical on the the reverse side. You plug your equipment into this device and in doing so, cheat the ground, They are not UL approved but most music equipment stores keep a few around.

How risky is that? It wouldn't be a big loss if my stereo equipment got zapped but my computer is somewhat expensive.

Very risky.

The ground conductor is there for a reason. If there is an electrical short, the charge will take the shortest path back to the earth, which is the proper function of the ground wire. In lieu of a ground wire, the charge will flow to the closest thing that conducts electricity--usually human skin.

YOU can be shocked, injured, and even killed by not following proper electrical grounding procedures. You can also die in a fire as the result of a wiring fault. If you can't provide a proper ground, don't hook it up. A ground lift is not something that you want to mess around with when you are dealing with AC mains power running 120 volts and 15 or more amps.

If you are going to lift the ground, do it on the audio circuit where the voltage is much lower. DON'T EVER USE A GROUND LIFT ON THE AC CIRCUIT.

 

[ultasax]

JC Bigler is obviously highly qualified & technically correct & that is why UL and CSA no longer approve them. However they are still in frequent use. I recommended the possibility not with the intention of putting you or your equipment in harms way. I have many in use and they have been in continuous service for years.

I use them for audio and low voltage loads. That doesn't mean that they are fail safe and perhaps I have just been lucky. Having JC Bilger's warning would certainly suggest trying the shielding idea on the long run first, and then perhaps others will weigh in on their experience with the ground lift device so you could decide if it's worth a try.....Just make sure your insurance is up to date, and that the family is out of the house along with any neighbours that you have or might form any affection for.

Just kiding, yeah, I know it's not phunny, But I can't help myself. I play my horn that way to, but then... they laugh.....

 

[tanbark813]

Having JC Bilger's warning would certainly suggest trying the shielding idea on the long run first, and then perhaps others will weigh in on their experience with the ground lift device so you could decide if it's worth a try.....Just make sure your insurance is up to date, and that the family is out of the house along with any neighbours that you have or might form any affection for.

:lol:

Given the risk I'd prefer just living with the buzz or using the work around in the OP rather than go that route.

 

[notes_norton]

Try two USB to Audio interfaces, they sound better than the little earphone jack anyway. You can probably pick up an old Edirol UA-1 on eBay for about $50 and a new one for under $70.

Radio Shack also makes an isolation transformer that you can put in the line between the computer and the stereo.

My home was built in 1950 and I had severe hum until I did both of the above, and now there is no hum at all.

Insights and incites by Notes

 

[TonyPhillips]

Try this; take a length of wire, ends stripped. Touch one end to the joint on one of the RCA plugs, and touch the other end to the metalic screw that holds the wall plate where your receiver is plugged in. If the noise decreases or goes away, it's definately a ground loop... Try also the other end where the PC is connected. (This only works if the screw is conductive, paint will keep this from working well.)

The outer "rim" of an RCA plug is "ground," the center pin is signal.

If your audio disappears ENTIRELY, then you have a "polarity" problem in your signal where signal and ground references are being reversed.

In electrical terms, there's no such thing as an ABSOLUTE ground. You just want the two ends of the signal (or three, in your case) to have the same REFERENCE ground.

If you're successful in stopping the noise via this method, then, if you're a propeller-head like me, you could take an RMS AC Voltmeter and measure the voltage from that screw to the RCA plug and see what the ground difference is. I've seen it as high as 5-6 volts before...

Now if that path is carrying substantial CURRENT (more than few milliamps), then you've got a bigger problem you need to fix. Call an electrician.

 

[stormott77]

I used to DJ a lot using my computer and I used a DI box to get rid of the hum.

 

[tanbark813]

Okay, I just ordered:

Xitel Ground Loop Isolator - GLI1S1

Shielded RCA cable

Behringer U Control UCA202 USB Audio Interface

Let's see how these sons o' bitches do.

 

[tanbark813]

***Update***

The USB audio interface arrived first. I hooked it up and there was no change with the buzz. I didn't expect there to be, just stating that for the record.

Next, I hooked up the ground loop isolator directly to the USB audio interface, before any of the cables that go to the two receivers. There was a noticeable reduction in the buzz. It reduced it by about 50 - 60%.

I then hooked up the shielded RCA cable to the living room receiver and the buzz was completely gone. I could crank the receiver up to its max--much louder than I would ever need it--and get no buzz.

Just out of curiosity, I disconnected the ground loop isolator after getting the shielded cable in place and the buzz returned a bit. It wasn't back to its initial level, but back to about half of what it was before.

So, the shielded cable and ground loop isolator each, by themselves, cut the buzz by about half but both of them together eliminated it altogether.

Thanks for the help.