Laptops connected to Amp - AVS Forum
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post #1 of 8 Old 06-22-2009, 02:33 PM - Thread Starter
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Hello, please could you help i have Amp connected to 2 laptops 1 comp and tv but when i dont have any sound playing on the laptops which is plugged into the headphone jack they seem to get electromagnetic interference Does any one know a way of stopping this? as i dont seem to get it on comp would using a USB sound card on the laptops instead work at all? thanks in advanced.
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post #2 of 8 Old 06-23-2009, 02:37 PM
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OK. Here's what I know.

First off, the environment inside a computer is absolutely terrible for an analog signal.

If you are hearing a rapid deet-deet-deet-deet (pause, and repeat) most likely you are hearing interference from the voltage converters in the machine.

one of the best notebook lines I have found for analog output of audio are MacBook Pro's (audiophile Apple notebook users, stop reading here, if you don't want me to spoil things for you...)

The only quibble I have ever had with apple audio output from their notebooks is that there is a slight pop as any sound starts playing. (I never noticed it till someone mentioned it, and now it is impossible for me to NOT hear it...) this is believed to be the audio output hardware being powered up. It is possible to prevent this from happening by keeping a quicktime window open, thus keeping the audio hardware active.

More than likely, most of the interference will go away as soon as you start running on battery power. I can also state for the record that the analog out on a Sound Blaster Audigy 2 ZS in a laptop cardbus slot also has this problem. I cannot be certain that a USB device will solve the problem, but your best bet would be to get a USB interface that draws power from a wall-wart rather than drawing off the USB bus alone.

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post #3 of 8 Old 06-23-2009, 02:52 PM
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Look into an Audio Interface such as M-Audio makes, where it's outside the computer and connected via USB. I would think the SN ratio should be improved on those things.

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post #4 of 8 Old 06-23-2009, 03:19 PM
 
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Quote:


i have Amp connected to 2 laptops 1 comp and tv

Most likely a ground loop.

Quote:


but when i dont have any sound playing on the laptops which is plugged into the headphone jack they seem to get electromagnetic interference

So, the interference goes away when you're playing something, from any of the devices?
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post #5 of 8 Old 06-28-2009, 04:48 PM - Thread Starter
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Thanks for the help guys


Quote:


So, the interference goes away when you're playing something, from any of the devices?

Well it seems to stay only with the laptops but its fine with the other things
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post #6 of 8 Old 06-28-2009, 05:43 PM
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I had the same problem until I got a new power supply. My new supply is bigger (wattage wise) but I think the major difference is that it has a ferrite core (choke?) on the power lead.
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post #7 of 8 Old 06-29-2009, 08:43 AM
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Pull the power cord and run the laptop on battery only...that should kill the noise.
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post #8 of 8 Old 06-30-2009, 06:12 AM - Thread Starter
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Thanks for the help yeah its fine when the laptop is just running on the battery.
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