DAC problem. Laptop AC causing disturbance to the sound.

Avatar86

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Jun 29, 2016
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Hello everyone! :)

I have a wonderful little Meridian Explorer 2 (USB DAC) which I like very much the sound of .

My problem occurs when I plug in the power cable to my Acer laptop. The sounds changes and is experienced by me as ... " fuzzier " / less distinct , messier when I have the power cord plugged in. If I take out the power cord the sound is smooth and quiet and nice. The same error occurs on my second laptop.

This problem does not occur on my desktop computer!

My guess is that the power supplies in notebook computers are too bad ... but I would like to know exactly what creates this problem.

Now it is not a question of grounding loops in the sense that there is a hum or noise in the speakers when the cord is in (I had this problem before, but DAC'en removed it actually) .

What do you think? it is a common error ? can you do to reach there or are they simply just run on battery or on the desktop ?

Sincerely // Micke
 

fas42

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Jan 8, 2011
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Micke, welcome to WBF! As regards your sound issue this is a common problem with digital playback - the circuitry, in the DAC, is too susceptible to interference effects, directly or indirectly. And how to solve it may be, yes, as simple as always running the laptop on battery power, whenever music is being played.

The actual, precise reason may be very, very difficult to track down - and ultimately probably rather pointless: the key thing is that the voltage waveforms, and power rails in the sensitive circuitry should be as "perfect" as possible, and how one achieves this will vary per system!
 

Avatar86

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Jun 29, 2016
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Thank you and Thank you :) Yes I believe you are right. It seems to me that there are no other way on laptops then to just run on the battery. Though! I would like to be able to use my computer for listening to musik for several hours an... well the battery just ain't that good :/

I totally digg your explanation about how fragile the sound through DACs can be. mostly this was the answer I was looking for, just to hear that it's a common issue and that there are no easy fixes to it. Unless someone has another opinion? Probably I have to get a really quiet Desktop to drive my DAC and speakers with. Should be better for watching movies as well. :)
 

fas42

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With my laptop, just using the internal sound system, I worked out that the best compromise was using the charger when it was actually actively charging, that is, the battery charge was less than 100%! Next best was battery only , with the charger unplugged; and worst was charger running, but the batteries were at 100%, so the charger was idling. So, the charger was injecting too much noise when it "had nothing to do", it needed its output circuitry being driven to feed strong current constantly to the laptop, to not cause a problem.

This is something you could perhaps try ...
 

Avatar86

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Jun 29, 2016
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I see! Nice that you found a sequence that works :D Cool!
unfortunately for me it did/ does not though :/ maybe my next laptop, I'll try!
 

opus112

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Feb 24, 2016
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My problem occurs when I plug in the power cable to my Acer laptop. The sounds changes and is experienced by me as ... " fuzzier " / less distinct , messier when I have the power cord plugged in. If I take out the power cord the sound is smooth and quiet and nice. The same error occurs on my second laptop.

From how you describe it, it sounds like you're experiencing common-mode noise issues. The noise being imposed by the laptop's switch-mode power brick between the mains supply and your audio ground.

This problem does not occur on my desktop computer!

It could be your desktop computer's power supply has an earth connection whereas your laptop's 'brick' does not. Earth connections don't solve the noise issues, but they do normally reduce them.

Now it is not a question of grounding loops in the sense that there is a hum or noise in the speakers when the cord is in (I had this problem before, but DAC'en removed it actually) .

Right, but it is still an issue of big loops of wire which exist between interconnected components (laptops and poweramps). Its not a DC ground loop, but it is a ground loop all the same.

What do you think? it is a common error ? can you do to reach there or are they simply just run on battery or on the desktop ?

Yes, very common. The solution is to either break the loop (which you do by powering the laptop from its internal battery) or raise the impedance of the loop significantly (by using suitable common-mode chokes or isolation).
 

Avatar86

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Jun 29, 2016
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From how you describe it, it sounds like you're experiencing common-mode noise issues. The noise being imposed by the laptop's switch-mode power brick between the mains supply and your audio ground.



It could be your desktop computer's power supply has an earth connection whereas your laptop's 'brick' does not. Earth connections don't solve the noise issues, but they do normally reduce them.



Right, but it is still an issue of big loops of wire which exist between interconnected components (laptops and poweramps). Its not a DC ground loop, but it is a ground loop all the same.



Yes, very common. The solution is to either break the loop (which you do by powering the laptop from its internal battery) or raise the impedance of the loop significantly (by using suitable common-mode chokes or isolation).

Yeah! I got similar answers from another forum actually.
But this "raise the impedance thing" how do you do that?
Common-mode chokes? Isolation?
Are these something you can buy? (link to image please)
or more like Settings?
Sorry :/ *n00b!* :)
 
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Ken Newton

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Dec 11, 2012
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Yeah! I got similar answers from another forum actually.
But this "raise the impedance thing" how do you do that?
Common-mode chokes? Isolation?
Are these something you can buy? (link to image please)
or more like Settings?
Sorry :/ *n00b!* :)

Raise the common-mode impedance of the power supply connection, or of the laptop to DAC interface. I agree with an earlier suggestion to simply run off battery power, to the degree that's practical in terms of operating time. If you require longer operating time than is made possible by your laptop's battery, then a commercial power conditioner is probably your next move. You likely can obtain an effective and inexpensive conditioner at your local office supply store. Power conditioners marketed specifically to audiophiles tend to be big $$$. The easiest way to impede the common-mode at the laptop and DAC connection is to utilize an optical interface, assuming that both units support optical.
 
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Avatar86

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Jun 29, 2016
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1. in another forum we discussed the possibility that this problem maybe due to the laptops battery charger unit that causes the distortions.
what do you think?

2. a USB Hub (supplied) was alsow a thought that this might work to get round this problem. What do you think?

I will try to buy on tomorrow and check. (it's returnable it it does not work so it's cool) :)

I'll post the results then.
 

Avatar86

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Jun 29, 2016
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Quote from another thred in a different forum, whereas you sould use a Supplied USB Hub or not:

"Use a good USB hub. belkin, okion, dlink all good brands, just make sure the power adaptor >3.5 amps for 7 port usb. the consistent power delivery will isolate the noise and power from the pc. try it, usb dac becomes so much more detailed and clear. come back and say thanks!"

might be worth a try :)
 

fas42

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Jan 8, 2011
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Micke, the "try it and see" approach I have found overall to be highly effective, provided you only spend spare change or less to set something up. Many times I have had quite bizarre behaviours, which don't make sense at the level of conventional thinking about electronic circuits - ultimately, it is all explainable, but measurement techniques are not developed enough as yet to clearly show what's happening. So, I generally don't worry about measuring, and at the moment leave the "I must know why!!" thinking in the ToDo basket ...
 

Avatar86

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Jun 29, 2016
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Micke, the "try it and see" approach I have found overall to be highly effective, provided you only spend spare change or less to set something up. Many times I have had quite bizarre behaviours, which don't make sense at the level of conventional thinking about electronic circuits - ultimately, it is all explainable, but measurement techniques are not developed enough as yet to clearly show what's happening. So, I generally don't worry about measuring, and at the moment leave the "I must know why!!" thinking in the ToDo basket ...

Cool :D
"Wa Da Tah" (Pootie Tang)
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
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Grounding issues are tricky to sort out
Does the laptop power brick mains plug have an earth?
Is the Explorer connected to an amp or headphones?
If an amp, try plugging the amp & laptop into the same mains outlet.
Another approach to try would be to run a heavy wire or grounding braid between the chassis of the laptop & the chassis of the amp/preamp

The reasoning behind these approaches is to redirect this ground noise away from the signal ground by providing an alternative low impedance & low inductance path for it to ground.
 

Avatar86

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Jun 29, 2016
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(damn my previous message dissapore :/ )

in short. ..

just got a desktop coputer and the sound is Amazingly much better on this one :D

The difference is like Night and Day!

Don't think I will ever listen to music on a laptop with the cord connected ever again.

*Very Happy*
 

Folsom

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Oct 25, 2015
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I knew a guy who made music that always got a ground noise. There's no transformer isolation in the laptop charger. I could make a small (safe) box that would block a loop. It worked for the other guy I knew. This may not be your problem. If your laptop charger doesn't have ground, it's not the issue.
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
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I knew a guy who made music that always got a ground noise. There's no transformer isolation in the laptop charger. I could make a small (safe) box that would block a loop. It worked for the other guy I knew. This may not be your problem. If your laptop charger doesn't have ground, it's not the issue.

Well, I'm not so sure about your statement that's highlighted?
With PSes but especially SMPS chargers there's a leakage current that can make it's way to the DC output (the floating output) so even if there's no mains ground connection on the charger a potential voltage difference between this floating ground & the grounds of other connected devices can result in current flowing on the ground & hence the ground noise issues as experienced by the o/p. This will only cause this noise issue under certain circumstances

This issue raised it's head in certain measurements recently by one whose name should not be mentioned :)
 

Billy Shears

Well-Known Member
Jul 27, 2015
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What you are hearing is the difference between a cheap switchmode psu powering the battery in your laptop VS just the battery.
I hear the same fuzzy effect when connecting the PSU to the Chord Hugo DAC VS just running on the Battery. Forget all the measurement ideas of Battery providing perfect isolation. Those cheap wallwart PSU allways screw up the sound one way or another.
 

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