Soundcard to Receiver - how to get rid of 'brumming' ?

[donpedro]

I am planing to build "Multimedia PC". In that process I was trying to connect my current PC to TV. Problem that I am having is that when sound is connected to receiver it makes some kind of "brumming" noise (sorry that I don't know better word to describe that sound).

Is there something that can be done about that ?

[muskgrave]

you are getting a very common interference..the best way to eliminate it is to get a sound card with a digital out ...you can get an m-audio card with a digital coax out and it will give you the cleanest signal with no hum.

dlv

[donpedro]

I thought about that (dig.out). No other solutions ???

[Nelson37]

Make sure sound card is set to Line-out and not Speaker-out. May require jumper setting. Also turn off any amplification on card, and set output volume very low, use receiver to amplify. Make certain RCA mini-plug is not making metal-to-metal contact with case. Sound cable not running over any power source.

Brumming??? Is that a Buzz and a Hum combined, or a way to clean the floor?

[donpedro]

Brumming??? Is that a Buzz and a Hum combined, or a way to clean the floor?

It's when it makes sound like "brum" next time I'll look it up in dictionary.

I will try your other sugestions

[jg0001]

You 'brumming' is prob a 60hz hum from an electrical ground loop problem. I had a similar problem (once). I could here it on ALL my 5.1 speakers (connected to my AV Receiver) but especially on the subwoofer. If you can hear it simply by turning up the volume on your receiver with NO other sound playing, this is likely your problem.

For me, it turns out the problem would go away the minute I disconnected the COAX input from my cable box (b/c my house has its own electrical 'ground' and the cable line 'ground' was slightly different -- not all 'grounds' are electrically the same). Try disconnecting ANY AND ALL connections that your cable box could make with your other equipment and see if the problem is solved. Disconnect the outside COAX from the cable box, UNPLUG the cable box (key!), disconnect any A/V wires plugged into your PC, etc. This will at least help you identify the source of the problem.

Now, if this WAS the problem, simply switching to a digital connection from the PC to the receiver may do the trick. It did NOT for me since I was using a digital coax connection. An OPTICAL connection probably would work, since there is no metal or ground line contact between the two devices. The problem I had with this is that you need to send the 6 analog 5.1 channels in analog as no SB Audigy card will ENCODE to digital, other than as stereo.

There are filters you can get for this, but in the end, I got a Monster Power Strip with filtering (I have a 12 outlet Home Theater Power Strip). These are a good thing to have anyway. I have one for my PC stuff and another for all my TV/Audio gear.

http://www.monstercable.com/power/lineHomePower.asp#PowerBars

[jg0001]

I have the Home Theatre POWERBAR 2100 with "Clean Power Stage 2" line filtering. I also pipe the coax lines thru it.

[donpedro]

If you can hear it simply by turning up the volume on your receiver with NO other sound playing, this is likely your problem.

Yes... when soundcard from PC is connected to receiver and so other sound is played I can hear that.

For me, it turns out the problem would go away the minute I disconnected the COAX input from my cable box (b/c my house has its own electrical 'ground' and the cable line 'ground' was slightly different -- not all 'grounds' are electrically the same). Try disconnecting ANY AND ALL connections that your cable box could make with your other equipment and see if the problem is solved. Disconnect the outside COAX from the cable box, UNPLUG the cable box (key!), disconnect any A/V wires plugged into your PC, etc. This will at least help you identify the source of the problem.

Good guide for identifying proble. Thanks. Anyway... As a solution I can use it since it should be "Multimedia PC" permanently connected to receiver and ready to play or capture from cable box.

...but in the end, I got a Monster Power Strip with filtering (I have a 12 outlet Home Theater Power Strip). These are a good thing to have anyway. I have one for my PC stuff and another for all my TV/Audio gear.

You spend almost all my budget on power connectors

[dphirschler]

Fogvie me if I am wrong, but wouldn't connecting a ground wire between the two devices solve the problem?


Darryl

[donpedro]

Fogvie me if I am wrong, but wouldn't connecting a ground wire between the two devices solve the problem?

How would I do that ? Is there any "guide" to where connect what ? It is from PC to Receiver setup for now. Additional components will be added later.

[dphirschler]

Find a metal screw on computer, connect a wire to it. Connect other end of wire to a metal screw on receiver. Find a good screw that is screwed into the metal housing. Sometimes the receiver will have a screw labeled "ground" just for this purpose.


Darryl

[OmegaSupreme]

I had a hum problem with my turntable (I was digitizing my LPs) that was fixed by using a set of high end MIT cables that are dual shielded and have noise suppression tech. The cables are pricey, but they work.

[dicktheprick]

i had the same problem, til i found my little xitel digital port. it is technically a usb sound card that has usb in to TOS link out. the thing works perfectly. Im sending my signal about 20meters and no humm to speak of. check it out at www.xitel.com. the thing is about $60US and makes for an easy setup. they also have ground loop isolators that work really well.

[donpedro]

dicktheprick, I wan't to avoid adding USB devices, but your link unveiled this litlle thing Ground Loop Isolator for $29.95.

I am going to try some of the "cheaper" sugestions first

[dicktheprick]

May i ask the reason why you are trying to avoid the USB device? The devices are a bit pricy, IMHO well worth it, absolutly ZERO hum.

[donpedro]

My plan is to use USB Capture/Tuner external MPEG2 encoder and it is recomended to avoid using other USB devices for better performance.

[muskgrave]

the external card with the optical out might be the best option there is. optical is immune to electrical interference.

dlv

[jg0001]

Did you identify the cable box or other source as the cause of a ground loop problem?

BTW, simply 're-grounding' all the cables won't solve your problem. In fact, it is the connection and 'circuit' created by the grounds touching one another that causes the hum in the first place. If you slowly connect the troublesome cable, you'll notice no hum when the signal wire is plugged in, but the moment the ground shielding touches the screw-on connector, the hum begins.

I spent a long time wrestling with this problem and the Monster power strips (though pricey) solved my problem without any fuss. All the other solutions I tried only reduced, but didn't eliminate, the hum. The 'littler strips with noise filtering cost about $150. The big one with 12 outlets is about $250.

[donpedro]

Did you identify the cable box or other source as the cause of a ground loop problem?

Not yet... It will require to move everuthing back from den to living room. I will do that during weekend.

[dicktheprick]

i can understand your concern for not using USB devices, but the reason they say not to use other devices, is that the amount of bandwidth will be limited, and we all know that audio bandwidth is a fraction of video, i dont think that there will be a problem. I just think its the easiest and Least expensive way to deal with the problem, unless you can afford a $150 power strip

[triphop]

This is ground loop interference. You probably have 50 or 60Hz on the cable or tv into your computer. This is the most common problem around. Here is a website that details this:

http://www.dplay.com/tutorial/cablehum.html

Buy the parts at radioshack or online at:

www.allelectronics.com

[dphirschler]

Again, I may be wrong... but I was under the understanding that the hum is caused by poor grounding. When the device is poorly grounded, then the ground travels through the shielding and thus becomes audible. If one of the devices is properly grounded, then connecting a ground wire between the two devices should properly ground the other device and your hum should go away.

It should be cheap to test it anyway. You probably have some wire lying around somewhere. In fact, you might be able to touch your finger to each device (using your body as the conductive connection) to test it.


Darryl

[cim]

Before you spend lots of $$$ on any additional equipment, try re-routing your cable... away from your TV, Monitor, Speakers... I think you'll be amazed how much that will help. If you notice an improvement, but can't quite eliminate all of the noise, get yourself some sheilded cables, they don't have to be $100 monster cables, just something with some good sheilding on them.

[triphop]

There are two ways to handle this - a strap to ground (what you suggest) or isolation (what I suggest). Do you know how much current is on that line? You have to be sure that your strap and ground return can sink that current. There are additional problems that can arise that can all be easily avoided with simply isolating the line. This is what *all* long run cables do - telephones, ethernet, firewire, etc, etc... If you pull to ground, you can have current loop issues...

[triphop]

$100 cables are a waste of money - you think that they spend that much on the cables in the studio?? Not. And if they don't, then why spend that much on your side. Properly shielded cables are largely immune to noise - the key is to isolate the inputs and you can run that sucker through your mictrowave and you will have no hum...

PS. I largely scoff at hyper expensive signal cables, speaker cables are outside my experience but I suspect that the expensive ones are also ways to parts fools and their money.

[dicktheprick]

i did notice less interference when i ran my speaker line perpendicular to any power cable, this has to do with the magnetic flux of the power cable and the induction of electricity in the speaker cable, so never run the power cables and speaker cables parallel with each other.

[jg0001]

I tried the 75-300 ohm workaround that triphop suggests... problem is that it then allowed in unacceptable levels of interference on the cale line (because you break the shielding, it starts to act like an antenna and it will pick up stray signals). You can wrap ALL the metal contacts between the converters in electrical tape and then wrap the whole thing with 20 layers of aluminum foil, but you'll still end up with a so-so situation.

I also tried ALL the other methods listed. Making sure all your cables are properly shielded, avoiding parallel runs to AC cords, using in-line groud loop breakers (bought one of these for about $70)... in the end, when I happened to grab a Monster Power Bar (with noise filtering) on sale it miraculously cleared up the problem and I 'uninstalled' all the other patch ups. Perhaps you can buy one where you can return it easily (Circuit City - and be careful when you open it) and try it out for yourself. All the other methods are a real hassel, especially if like me you have a dozen devices all plugged into one another.

[proxyx99]

As indicated this is a grounding issue. One of the devices in the loop is not properly grounded. Isolate the problem by simplifying config. plugging and unplugging cables/coaxes etc., test with other input sources, test TV output through a receiver or amp.