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PostPosted: December 15th, 2017, 1:32 pm 
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Joined: February 19th, 2017, 9:43 am
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SoundMods wrote:
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.


If the laptop is driving a DAC it is more likely that the noise is on the AC line and affecting the DAC, not the laptop.

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


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PostPosted: December 15th, 2017, 1:43 pm 
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DaveR wrote:
SoundMods wrote:
Cogito wrote:

Plug in the laptop charger into the power conditioner.


If the laptop is driving a DAC it is more likely that the noise is on the AC line and affecting the DAC, not the laptop.

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


DACs usually have LPS. Most likely the AC noise effecting the laptop which is cascading to USB power.

_________________
Shashi


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PostPosted: December 15th, 2017, 1:55 pm 
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I'd be surprised if this is the case. The noise would be common mode by the time it got to the USB port.


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PostPosted: December 15th, 2017, 3:46 pm 
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My suggestion is to listen to it with battery power and charge when not listening. My MacBook Pro sound better in battery mode compared to charging mode even though I hear no noise in either mode.

Some DAC receivers do not need the 5v+ USB leg, if your DAC is one of these you could run a data only USB cable.


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PostPosted: December 15th, 2017, 4:07 pm 
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TubeDriver wrote:
Some DAC receivers do not need the 5v+ USB leg, if your DAC is one of these you could run a data only USB cable.


Even of it does need the +5V line, build a 5V linear supply and splice it in instead of getting the +5V from the laptop....

Roscoe


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PostPosted: December 15th, 2017, 4:13 pm 
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For the moment, I am doing as you suggest and just use battery power. The ODAC gets its power from the USB connection.

In the meantime I will try to come up with something using one of my LT1083 regulators.

ray


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PostPosted: December 15th, 2017, 4:16 pm 
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Roscoe Primrose wrote:
TubeDriver wrote:
Some DAC receivers do not need the 5v+ USB leg, if your DAC is one of these you could run a data only USB cable.


Even of it does need the +5V line, build a 5V linear supply and splice it in instead of getting the +5V from the laptop....

Roscoe


I will look into it. Probably a better all round solution.

ray


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PostPosted: December 15th, 2017, 5:12 pm 
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You can find LT1083 based variable output regulator kits on EBay, good to 7amps. Very low noise and 18.5VDC is in the adjustment range. Already have bridge rectifiers. They are LDO regulators, so a 15vac 120va power transformer should be within the heat dissipation range.

Just a thought.


Last edited by HAL on December 15th, 2017, 5:40 pm, edited 1 time in total.

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PostPosted: December 15th, 2017, 5:21 pm 
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HAL wrote:
You can find LT1083 based variable output regulator kits on EBay, good to 7amps. Very low noise and 18.5VDC is in the adjustment range. Already have bridge rectifiers. They are LDO regulators, so a 18vac 120va power transformer should be within the heat dissipation range.

Just a thought.


At under $12, it probably is a good simple solution. I'll make my mind up tomorrow. With a glass of single malt in hand watching the snow, decisions are best left postponed for a day.

ray


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PostPosted: December 15th, 2017, 5:37 pm 
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If you can find an E-I core power transformer, the will limit bandwidth both directions.


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