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PostPosted: December 15th, 2017, 10:14 am 
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Joined: January 14th, 2015, 11:15 pm
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For various reasons I have needed to change to an old HP laptop. It uses a 120 watt, 18.5 v 6.5 amp charger. It runs Windows 10 and I use Jriver.

Everything is fine except that I get noise coming thru my usb ODAC when the charger is connected. There is no noise when I disconnect the charger and use the internal laptop battery.

I could buy a replacement charger but I suspect that the problem may be internal to the laptop and not in the power supply. Any ideas?

On a separate note, I seem to remember a website that listed Windows services that could be turned off but I cannot remember what it was. Does anyone have recommendations?

ray


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PostPosted: December 15th, 2017, 10:26 am 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
ratbagp wrote:
For various reasons I have needed to change to an old HP laptop. It uses a 120 watt, 18.5 v 6.5 amp charger. It runs Windows 10 and I use Jriver.

Everything is fine except that I get noise coming thru my usb ODAC when the charger is connected. There is no noise when I disconnect the charger and use the internal laptop battery.

I could buy a replacement charger but I suspect that the problem may be internal to the laptop and not in the power supply. Any ideas?

On a separate note, I seem to remember a website that listed Windows services that could be turned off but I cannot remember what it was. Does anyone have recommendations?

ray



I believe that your PC has a switch-mode power supply (charger) and although your PC theoretically should only "see" the battery, whether you are plugged in or not, it's possible that power-supply noise is getting through. You might build an aggressive RFI/EMI filter to fit between your power supply and PC -- or build or buy a high-quality linear power supply.

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PostPosted: December 15th, 2017, 10:31 am 
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Seems like building the linear power supply would be the way to go. I should have the parts kicking around.

ray


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PostPosted: December 15th, 2017, 10:43 am 
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Joined: February 28th, 2013, 3:31 pm
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This is an interesting problem that I have had with some DACs and not others even with the same PC and power supply. I don't know why that would happen. Might have something to do with the grouding in the DAC. Has anyone found a concrete reason why this happens?

Tom


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PostPosted: December 15th, 2017, 10:46 am 
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Joined: February 19th, 2017, 9:43 am
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I suspect it's radiated noise, not conducted noise.


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PostPosted: December 15th, 2017, 10:49 am 
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Joined: July 17th, 2016, 6:24 am
Posts: 356
ratbagp wrote:
For various reasons I have needed to change to an old HP laptop. It uses a 120 watt, 18.5 v 6.5 amp charger. It runs Windows 10 and I use Jriver.

Everything is fine except that I get noise coming thru my usb ODAC when the charger is connected. There is no noise when I disconnect the charger and use the internal laptop battery.

I could buy a replacement charger but I suspect that the problem may be internal to the laptop and not in the power supply. Any ideas?

On a separate note, I seem to remember a website that listed Windows services that could be turned off but I cannot remember what it was. Does anyone have recommendations?

ray


Plug in the laptop charger into the power conditioner.

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"Based on my experience" -or- "What I read on line" -or- "In my opinion" -or- well you get my drift here.


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PostPosted: December 15th, 2017, 10:55 am 
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Joined: February 19th, 2017, 9:43 am
Posts: 155
Cogito wrote:

Plug in the laptop charger into the power conditioner.


Or a simple power line filter. After my last post it occurred to me that when I installed the switching supplies in my amps I had to put in power line filters so the X10 modules that were nearby would continue to function. I used these:

https://www.amazon.com/gp/product/B016EJ5DU2/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

I also have some in-line and enclosed TEMPEST filters that might work for you. You can just plug them in the wall and the power supply into it. These will trip a GFI outlet or breaker, but should clean up the noise back into the AC well.


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PostPosted: December 15th, 2017, 10:59 am 
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Joined: January 14th, 2015, 11:15 pm
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DaveR wrote:
I suspect it's radiated noise, not conducted noise.


I moved the power pack away from everything else electrical by at least four feet with no improvement. Worth a try however.

ray


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PostPosted: December 15th, 2017, 12:43 pm 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
tomp wrote:
This is an interesting problem that I have had with some DACs and not others even with the same PC and power supply. I don't know why that would happen. Might have something to do with the grouding in the DAC. Has anyone found a concrete reason why this happens?

Tom


Not all electronics designers understand the issues with RFI/EMI issues. When I did an office building for a past employer, the access-control system was always going bonkers especially after a storm. But a storm wasn't necessary for shit to happen. When I set up a ladder to go into the ceiling to open up one the control panels there was no protection from anything. The engineering department at the security company could not understand why -- they commented that the power supply had three-pin regulars. OUCH! I guess ignorance is bliss. Three-pin regulators will reject ripple, but act as unity-gain amplifiers for anything else. Once I forced them to add Corcom RFI/EMI filters together with metal oxide varistors all was well.

It was not fun coming to work in the morning with a "lynch mob" waiting to get into the building. Employees were not issued keys because it was secured facility. When the access control system goes amuck it is definitely secured.

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PostPosted: December 15th, 2017, 12:45 pm 
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Location: Parkville, Maryland
Cogito wrote:
ratbagp wrote:
For various reasons I have needed to change to an old HP laptop. It uses a 120 watt, 18.5 v 6.5 amp charger. It runs Windows 10 and I use Jriver.

Everything is fine except that I get noise coming thru my usb ODAC when the charger is connected. There is no noise when I disconnect the charger and use the internal laptop battery.

I could buy a replacement charger but I suspect that the problem may be internal to the laptop and not in the power supply. Any ideas?

On a separate note, I seem to remember a website that listed Windows services that could be turned off but I cannot remember what it was. Does anyone have recommendations?

ray


Plug in the laptop charger into the power conditioner.


That won't work. The power conditioning has to be between the laptop and the switch-mode power supply.

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