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Interference from computer to amp


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Hi, im wondering if anyone can help. Ive recently bought a new desktop pc and im getting a lot of nasty noises (screetching, crackly noises) from my speakers when the amps turned on. It had stopped doing it but its back with a vengeance. It even seems to go through the vga cable to the tv then from the tv via phono cables to the amp.

Ive tried installing a sound card as originally the pc just had onboard sound. Ive also tried a cheap usb sound card. Ive tried swapping power cables and plugging everything into the same socket. Its driving me mad! Im going to try and get another psu to try to see if that stops it. Ive seen you can buy separate DACs, would that stop it? Thanks in advance for any help!

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It could be your amp. Try this to determine. Disconnect all input to your amp. Turn on your computer and amp. If you still hear noises, it shoul be your amp. Your amp is not built to resist external interference.

 

I have a small headphone amp I assembled. It used to pick up noises from my laptop. So I wrapped up internal circuit with small cables. The noise disappeared. I think you cann't do this. You may place your computer away from your amp.

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If both your PC and Amplifier use 3 Pin mains plugs, try connecting a wire between the metal cases of both.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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Sounds like a grounding issue. Try using a different outlet. Do both use a three pin plug?

Also, most power supplies have two wire output.

If you are hands on, look at the amplifier grounding. Putting a low value resistor between the electrical and physical ground will stop noise. Ten ohms is plenty. Lower better. But if you do not Feel comfortable with this, leave alone.

 

2012 Mac Mini, i5 - 2.5 GHz, 16 GB RAM. SSD,  PM/PV software, Focusrite Clarett 4Pre 4 channel interface. Daysequerra M4.0X Broadcast monitor., My_Ref Evolution rev a , Klipsch La Scala II, Blue Sky Sub 12

Clarett used as ADC for vinyl rips.

Corning Optical Thunderbolt cable used to connect computer to 4Pre. Dac fed by iFi iPower and Noise Trapper isolation transformer. 

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Yes, its just plugged from the headphone jack on the back of the computer. Changing the sound on the computer doesnt affect the volume of the interference. Im thinking its some sort of grounding issue as the noise happened when amp was plugged into laptop but stopped once the laptop was unplugged and running off the battery

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Test if your TV is the source of inducting noise signal from your computer. Connect everything. But disconnect input to your TV and turn on everything. If you still hear the noise, your TV might be the one that receives the coumputer noise.

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Questions of the OP:

 

How many AC prongs are with the laptop power supply, 2 or 3? If a 2, AC noise is coupled to the common on the laptop's headphone out and also generates a nasty voltage to safety ground. Changing this PSU to a 3 prong helps, Belkin are OK.

 

A transformer in line with the audio out from the laptop may be the only choice since the 3 prong power supply doesn't get rid of hum & buzz noise completely. Can also be used with a future DAC (RCA). No real loss of fidelity these days or drop of signal come to think of it. I found the headphone connector unclean and causes scraping noises when you turn, a contact cleaner from RadioShack works very well, or isopropyl alcohol wipes or liquid. The signals are very small, so clean connectors are essential to avoid any losses.

 

Is your antenna connection from a cable system, or does it have distribution amplifiers? A good cure to remove noise is a cable filter from Jensen. I have these on the FM lines and no loops occurring.

AS Profile Equipment List        Say NO to MQA

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Disconnect input to your TV but connect everything else, if you still have noise, there are two possibilities. Your TV is conducting noise. Or the cable between TV and amp is working like antenna conducting noise. To test your TV is the problem, hear from the headphone jack directly using headphones. If it's ok, then the problem is with the cable in between TV and amp. Move around the cable position. If you hear noise level changes, the problem must be the cable. There isn't much to fix this other than place the cable so that it affects least.

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The OP has already verified that it's O.K. with the laptop unplugged and running off batteries.

It's a mains earth loop of some kind, or a PC PSU related problem.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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It most probably is the PC power supply that's causing the problem. However you could also try changing the PCI slot that the sound card is in to see if that changes anything. Trying another cable might also help. I've had cables that worked fine with certain gear and not others.

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It most probably is the PC power supply that's causing the problem. However you could also try changing the PCI slot that the sound card is in to see if that changes anything. Trying another cable might also help. I've had cables that worked fine with certain gear and not others.

 

jhinton said " Ive also tried a cheap usb sound card."

 

USB sound cards appear to be only external devices that are +5V USB bus powered.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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