theres nothing around it...

a possibility is some metals or interaction with the stuf inside is making that sound? cable box, tv, phone are the only things that are on but they still 5 feet away at least
 
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Proud To Have A Winddancir Original

thanks for the help robbie ill try to fix it
 
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Not exactly. The base components may be similar, but the main difference between a cheap and expensive system is simply the quality(and quantity) of the capacitors inside.
Capacitors attempt to keep the voltage constant, though if they are cheaply made and leak, or simply not there, you get some problems.

The hum is most likely not the charger. It is most likely the charge-controller inside your laptop itself. Also, I am guessing that the reason you hear it is that the audio module does not have any filter caps on the power coming in, or the caps have failed.
As far as age, my current IBM T41(2005) does not exhibit any sort of audible noise over the speaker system or otherwise, plugged in or not. I say current, because I had another one which I used for a good three years, before its internal charging system failed. Before it failed, sometimes while charging, it would make noise... but not over the speakers. It would make a high-frequency barely audible noise, which appeared to be coming from one of the inductors in the charging system.

However, the issue is not whether or not your power supply has noise on its output, its whether the audio system is able to filter that noise out before it gets modulated into the analog audio signal.

This is a different phenomenon. This is not noise being introduced through the power that feeds the audio output circuit, this is noise most likely being magnetically induced into the cables of the PA system.

Yes, though as I stated earlier, it should have been filtered out in the audio circuit.
And this is the problem with the high-impedance input of the monitor. Unlike a lower impedance set of earphones or unpowered speakers, the high-impediance input causes only a tiny bit of power to flow with the signal. A minor ripple introduced from outside can become a big problem, as it gets magnified.


Still, no matter how good or poor the system is, It seems to me that the best thing to do is to use a resistor or two to on the signal lines. This will pull more power through the system, and may very well mitigate the noise leaking into the system.
 
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As my dad found out recently, a good, cheap portable AM radio(you may want to get an older - 70s-90s one) without noise-canceling is great for looking at relative noise levels. Tune it to the lowest frequency, and play around with it. It seems that it picks up 60hz(or a harmonic of it) fairly well; we were able to trace a 110v AC line buried under 12-18" of gravel with it quite easily.

I agree. The idea however is to make it clean enough so its not audible over the noise of the computer fans and other noise, which isn't hard to do.

Now I learned something. What sort of chips do you work with? I have an Audigy 2 ZS sound card(old, but I like it), and while it hasn't given me any trouble, I would like to know if there are any options like that on my system.



That reminds me. My computer isn't perfectly grounded, and there seems to be a small amount of stray EMI in my room; by touching one contact of my earphones and touching the second to my computer chassis(aluminum, clean), I get a very audible 60hz buzz.
The good part is that, when fully plugged in, there is -no- buzz(sound or no); I guess that is due to my card having a whole lot of capacitors. Mind you, these headphones are 64Ω.
 
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As my dad found out recently, a good, cheap portable AM radio(you may want to get an older - 70s-90s one) without noise-canceling is great for looking at relative noise levels. Tune it to the lowest frequency, and play around with it. It seems that it picks up 60hz(or a harmonic of it) fairly well; we were able to trace a 110v AC line buried under 12-18" of gravel with it quite easily.

I've seen that on TV where they go to show the amount of RF noise that comes off of CFL light bulbs. A long wave signal like that should have no problem getting through great distances of rock or concrete. Sadly the microwave frequencies like your cell phone, wireless router, satellite TV probably wouldn't stand much of a chance even with just a foot of rock or cement.

I agree. The idea however is to make it clean enough so its not audible over the noise of the computer fans and other noise, which isn't hard to do.

No it shouldn't be tough at that sensitivity anyways. Usually though, the deciding factor for how things get done is cost. If you can save 1 cent over a million units, you're talking about serious production savings. Things are just that competitive now.

Now I learned something. What sort of chips do you work with? I have an Audigy 2 ZS sound card(old, but I like it), and while it hasn't given me any trouble, I would like to know if there are any options like that on my system.

I work with the front end of set top boxes for your satellite tv and cable tv. Front end meaning the first area the received satellite TV signal goes when it comes in from the low noise block on the satellite dish. So that's the tuner and the demodulator.

I really don't know if that would be something that would be worked into your sound card or not. The technology definitely existed when your card was made. One of the demod's that I work with right now is almost 20 years old and it has the capability. There's a specific couple of register values I have to set to switch between impedances. The question is, would they expose that setting at such a high level of software that the user would be able to change it? Probably not. Just out of simplicity's sake there are a number of features that are hidden in any piece of software and an even larger number of hidden register values even at the low level driver code.

In the lab I was playing around an oscilloscope. I didn't attach the ground clip on the probe to anything but I put the probe on my hand. Apparently I have an 8V p-p 60 Hz signal

If you want to filter a signal, you need *usually* a resistive network to go around the capacitors. Otherwise you pretty much just end up with a DC block or an integrator or some sort depending on the situation.
 
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