Laptop noise with USB powered DAC

[LuzArt]

Have been playing with a USB powered DAC. Headphone amp no probs, no noise whatsoever. Switch to Lightspeed and power amp, horrendous buzz and hum. Pull power on laptop and run on battery, silent background. 

 

So aside from getting potentially little time out of the laptop battery, what are my options? The DAC is a Schiit, had already considered their Wyrd de-crapifier which injects cleaner power and disengages laptop power on the USB path, but is there a simpler solution with say a different power supply? 

 

Cheers

Ben

[AccuTidal]

I think you can invest in an USB passive or active filtration. Alternatively get a decent LPSU for your laptop. If you are handy with soldering and putting electronic parts together, i can assist with guiding you to butcher up a compatible LPSU for your laptop.

 

 

Edited April 17, 2020 by Chanh

[LuzArt]

Thanks Chanh, it's a Lenovo with a funny DC input, not sure if it's butcherable? 

[AccuTidal]

5 minutes ago, LuzArt said:

Thanks Chanh, it's a Lenovo with a funny DC input, not sure if it's butcherable? 

On the ps modulus.., can you post a photo of its back with input/output specs? 
 

If I am not mistaken, often is 19Vdc @ 3A. Building the lpsu, won’t be hard, nor sourcing the suitable connector/termination at Mouser, RS,.... 

 

With a decent LPSU, you will appreciate the SQ noticeably better. 

[LuzArt]

Sure...

 

 

[AccuTidal]

Great. Its 20Vdc @ 3.25A. A tranny of 120VA can do the job nicely. 

[aussievintage]

Sure sounds like a ground loop to me.  If you run the laptop from an isolation transformer, you'll probably fix it.  Also audio isolation transformers in the analogue interconnects should also fix it.

[rand129678]

3 hours ago, LuzArt said:

Switch to Lightspeed and power amp, horrendous buzz and hum.

If you touch the laptop, does the buzzing disappear?

 

 

[LuzArt]

45 minutes ago, rand129678 said:

If you touch the laptop, does the buzzing disappear?

 

 

Haven't tried that, but as it's plastic I'm not sure it would make a difference?

[rand129678]

1 hour ago, LuzArt said:

Haven't tried that, but as it's plastic I'm not sure it would make a difference?

What about touching amp?

[Guest DrSK]

5 hours ago, LuzArt said:

Have been playing with a USB powered DAC. Headphone amp no probs, no noise whatsoever. Switch to Lightspeed and power amp, horrendous buzz and hum. Pull power on laptop and run on battery, silent background. 

 

So aside from getting potentially little time out of the laptop battery, what are my options? The DAC is a Schiit, had already considered their Wyrd de-crapifier which injects cleaner power and disengages laptop power on the USB path, but is there a simpler solution with say a different power supply? 

 

Cheers

Ben

Definitely sounds like a ground loop issue to me. I'd say your headphone amp is floating whereas your other gear is grounded. A dead giveaway would be if your power amp / Lightspeed have a ground pin on the power plug into the wall. Don't be tempted to chop the third pin off on the plug. This can be dangerous if your gear develops a fault. 

 

A ground loop ocurrs when a single device has more than one path to ground. Commonly arises when multiple gear is connected and each running off the mains.

 

A few suggestions here already. Running off the battery is obviously cheap and effective. I always run off my Surface battery anyway as the power supply is more stable and DC to begin with. 

[LuzArt]

10 hours ago, DrSK said:

Definitely sounds like a ground loop issue to me. I'd say your headphone amp is floating whereas your other gear is grounded. A dead giveaway would be if your power amp / Lightspeed have a ground pin on the power plug into the wall. Don't be tempted to chop the third pin off on the plug. This can be dangerous if your gear develops a fault. 

 

A ground loop ocurrs when a single device has more than one path to ground. Commonly arises when multiple gear is connected and each running off the mains.

 

A few suggestions here already. Running off the battery is obviously cheap and effective. I always run off my Surface battery anyway as the power supply is more stable and DC to begin with. 

Thanks for your input, appreciated.

The Lightspeed is running off a battery. 

Using my spdif DAC, no noise at all. It has a separate PSU. 

13 hours ago, rand129678 said:

If you touch the laptop, does the buzzing disappear?

 

 

Haven't tried that, but as it's plastic I'm not sure it would make a difference?

[aussievintage]

12 minutes ago, LuzArt said:

Using my spdif DAC, no noise at all. It has a separate PSU. 

If you are using optical then that is the isolation that eliminates the ground loop.

[LuzArt]

On 18/04/2020 at 8:36 AM, aussievintage said:

If you are using optical then that is the isolation that eliminates the ground loop.

No optical available. 

[Steffen]

I’m getting a hum/buzz as well, when my laptop is running on grounded AC. There is no other grounded device in my system – router, amp, DAC and sub all have two-prong AC supplies.

 

Not surprisingly, when I run the laptop on battery the noise disappears. Surprisingly, the noise also disappears when I connect the laptop power supply (MacBook Pro 85W AC adapter) without ground.

 

I suppose that ground loops are possible even without ground pin, somewhere upstream the ground and N leads are likely connected.

 

[aussievintage]

4 minutes ago, Steffen said:

I suppose that ground loops are possible even without ground pin, somewhere upstream the ground and N leads are likely connected.

Yes, we use a multiple earthed neutral (M.E.N.) system for power distribution. http://www.electricalaxis.com/2016/10/what-is-multiple-earthed-neutral.html

 

[Steffen]

There you go, just one grounded device will create a ground loop, with your entire neighbourhood as catchment area for electromagnetic dirt...  

[pete_mac]

You could look at a USB isolator, but the high-speed versions required for most modern USB DACs aren't super-cheap:

 

https://hifimediy.com/product/hifime-high-speed-usb-isolator/

 

The older full-speed versions work fine with older USB DACs in my experience - I have a few cheap ADUM4160-based ebay spec isolators and they do a great job re: ground loop related noise.

 

https://hifimediy.com/product/usb-isolator/

 

https://www.ebay.com.au/itm/1PCS-NEW-USB-Isolator-1500v-isolator-ADUM4160-USB-to-USB-NEW-M78/222171395671?hash=item33ba727657:g:KCAAAOSwltxcRWGU

 

 

[LuzArt]

I've got a Schiit Wyrd on it's way, nothing but great reports for noise isolation and reclocking data. I'll report back. 

[Steffen]

16 minutes ago, LuzArt said:

I've got a Schiit Wyrd on it's way, nothing but great reports for noise isolation and reclocking data. I'll report back. 

Please do, I’d be very interested in your findings. 

[LuzArt]

The Wyrd hasn't removed the laptop power noise, although it isn't as bad as without the Wyrd inline. I noticed less noise when I remember the media player and hard drive wall warts from the board. So for now it's laptop battery only, might buy a spare or two for longer playback time, although I'm getting 4 hours minimum as it is. 

 

Thanks for everyone's help. 

 

Cheers

Ben

[aussievintage]

3 minutes ago, LuzArt said:

The Wyrd hasn't removed the laptop power noise, although it isn't as bad as without the Wyrd inline. I noticed less noise when I remember the media player and hard drive wall warts from the board. So for now it's laptop battery only, might buy a spare or two for longer playback time, although I'm getting 4 hours minimum as it is. 

 

Thanks for everyone's help. 

 

Cheers

Ben

 

You need audio isolation  transformers. I mentioned it earlier.  They sell cheap ones for use in cars - just a box with flying RCA leads,   at least to prove it will work, then maybe get better quality.