Bad hum from Audigy card when connected to Home A/V.

[Guest]

If I isolate the Tv system from the audio system no noise but then I cant use my surround sound while the computer is plugged in!

Shoreway,

This is exactly the information I was looking for when I said:

One thing to try is Plug the PC + monitor into the same outlet as the stereo, and make sure there are NO peripherals other than bus powered mouse and keyboard plugged into it.

Note that in this instance a TV with cable hooked to it would have been one of the peripherals I was referring to.

It may have seemed very subtle to you at the time but this step is critical in troubleshooting the hum problem.

In fact it is very very common to get ground loops through the cable for cable TV. This is because the shielding is typically earth grounded back at the utility pole, sometimes where it enters the home if you are extra special. Your A/V equipment will tyically be earthed at the service entrance of your home with a big copper rod driven into the ground. This situation creates a large ground "loop". If I am right then with all other gear hooked up in a star config as I described, by unplugging the cable TV cable the loop will be broken and the hum will disappear, and thus the reason I had suggested unplugging everything but what is needed.

If this turns out to be your problem there are commercially available video isolation solutions which go inline with the coax.

 

[ShorewaySaint]

The 50' quad-shield coaxial (with LR RCA ends) I am using is for line-level signal... that circuit is perfect!!! The noise seems to be introduced from the cable company Adelphia. My next step is to disconnect the cable while all A/V is connected just have not had the time yet.

 

[casewhite]

Let an old fool make a suggestion here . I was certified as a power generation and transmission systen relay engineer in 1975. You obviously have a ground loop in the system. In tube stereo systems the drill is to isolate each source using an isolation transformer the way hospitals do for their most sensitive equipment. A 250va tripplite will cost you about $75 a 1kva about $150. You don't need to shell out the extra money for the hospital plugs since what you have is digital and not sensitive enough to warrant the extra expencse. check the continuity of your cable ground/shield since you pulled it through the attic. It is not uncommon for nicks or separations to occurr. Make sure you don't parallel any AC circuits in the attic. Cross AC condutors at a90 degree angle. Since it seems to be ok when you have the TV disconnected, isolate that power supply first. If that doesn't work then the ground loop is internal to the TV usually in the picture tube section and there is little you can do except try a wireless connection. Also it is not clear. Did you run a video connection from the computer to the TV. If so lifitng that will cure the problem. It is very common for the loop to come in through the cable system If that is the case then hthere is very little you can do . It also occurrs with satellite dishes as well. If it is comming from adelphia then it is resonating in ythe video circuit. Do you have HDMI compatiblity since that would isolate the video stream from the audio circuits assuming the source is not internal to the cable box.

 

[ShorewaySaint]

I apologize for being so sluggish regarding this problem, I am thoroughly enjoying my mp3's without my surround sound plugged in so it has not been a priority. The main sticking point in regards to the ground loop from the coaxial I have yet to unplug the cable connection from the TV while having the DVD hooked up to the Stereo, that alone will tell volumes. I will post when I accomplish that. I am not sending Video through the wall but my cable is split to the computer and then the TV.

 

[mesarectifier]

I'm sure you're using good quality cable, but 3 rooms distance gives your high end ample chance to escape, meaning you have to put on more treble on the amp, which usually sounds artificial.

 

[Guest]

The subject at hand here is hum (usually 60Hz coupled onto the audio system, in this case I have assumed it is a ground loop) not the loss of treble. I am sure though it would be quite amusing to hear about the various high end escape paths. Let me guess: nicks in the insulation supply escape hatches? lol

 

[mesarectifier]

Let me guess: nicks in the insulation supply escape hatches? lol

It's a figure of speach, Jim.

If you're in an area of high interference there may be no solution (I am in a high interference area and I haven't found any solution.)

When I play my guitar, it acts as almost an aerial for interference, with more in some areas and less in others. The massive transformers in my Mark IV Boogie also seem to do this.

Back to PCs, my Hi-Fi is about 3-3.5m from my main PC. I use good quality cable to connect, but there is still quite a lot of hum that just seems to find it's way into the cable (another figure of speech, not the escape hatches this time lol). When I use shorter cables, there is next to no noise.

Just my experiences. It'd be great if someone could sort that one out for me, too actually

 

[ilikecomputers]

what is your amp

 

[Vokofpolisiekar]

I'm no technical expert, but my friend phoned me tonight and said that he was experiencing a low hum on his z5500's using Digital out (Din to Coaxial) through Live! 24bit in a media center setup. What he neglected to tell me was that he used dual view briefly with CRT and normal TV, after which he left the montior intact.

A few years ago I experienced the same problem, but with analogue speakers. My problem was specific in that my X800XT was generating something that bothered my Audigy2 seeing that I used the slot adjacent to my gcard. I moved two spaces down and voila - humming gone.

In my friends case, the monitor was next to the computer case, and hence the disturbance that caused the sound card to "hum".

It would seem that from these two options, that the sound card is highly susceptive to interference. Especially if you are running long distance, and I'm willing to put my neck on the block that the extension passes geyser and main AC supply distribution network for lights - a sure way to pick up interference.

 

[Mousemonkey]

This topic has been closed by Mousemonkey