LuzArt Posted April 17, 2020 Posted April 17, 2020 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 Posted April 17, 2020 Posted April 17, 2020 (edited) 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 Posted April 17, 2020 Author Posted April 17, 2020 Thanks Chanh, it's a Lenovo with a funny DC input, not sure if it's butcherable?
AccuTidal Posted April 17, 2020 Posted April 17, 2020 On 17/04/2020 at 5:47 AM, LuzArt said: Thanks Chanh, it's a Lenovo with a funny DC input, not sure if it's butcherable? Expand 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. 1
AccuTidal Posted April 17, 2020 Posted April 17, 2020 Great. Its 20Vdc @ 3.25A. A tranny of 120VA can do the job nicely. 1
aussievintage Posted April 17, 2020 Posted April 17, 2020 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. 2
rand129678 Posted April 17, 2020 Posted April 17, 2020 On 17/04/2020 at 5:39 AM, LuzArt said: Switch to Lightspeed and power amp, horrendous buzz and hum. Expand If you touch the laptop, does the buzzing disappear?
LuzArt Posted April 17, 2020 Author Posted April 17, 2020 On 17/04/2020 at 8:41 AM, rand129678 said: If you touch the laptop, does the buzzing disappear? Expand Haven't tried that, but as it's plastic I'm not sure it would make a difference?
rand129678 Posted April 17, 2020 Posted April 17, 2020 On 17/04/2020 at 9:27 AM, LuzArt said: Haven't tried that, but as it's plastic I'm not sure it would make a difference? Expand What about touching amp?
Guest DrSK Posted April 17, 2020 Posted April 17, 2020 On 17/04/2020 at 5:39 AM, 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 Expand 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 Posted April 17, 2020 Author Posted April 17, 2020 On 17/04/2020 at 11:23 AM, 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. Expand 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. On 17/04/2020 at 8:41 AM, rand129678 said: If you touch the laptop, does the buzzing disappear? Expand Haven't tried that, but as it's plastic I'm not sure it would make a difference?
aussievintage Posted April 17, 2020 Posted April 17, 2020 On 17/04/2020 at 10:23 PM, LuzArt said: Using my spdif DAC, no noise at all. It has a separate PSU. Expand If you are using optical then that is the isolation that eliminates the ground loop. 1
LuzArt Posted April 20, 2020 Author Posted April 20, 2020 On 17/04/2020 at 10:36 PM, aussievintage said: If you are using optical then that is the isolation that eliminates the ground loop. Expand No optical available.
Steffen Posted April 20, 2020 Posted April 20, 2020 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 Posted April 20, 2020 Posted April 20, 2020 On 20/04/2020 at 11:13 PM, Steffen said: I suppose that ground loops are possible even without ground pin, somewhere upstream the ground and N leads are likely connected. Expand 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 1
Steffen Posted April 20, 2020 Posted April 20, 2020 There you go, just one grounded device will create a ground loop, with your entire neighbourhood as catchment area for electromagnetic dirt...
pete_mac Posted April 20, 2020 Posted April 20, 2020 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 Posted April 20, 2020 Author Posted April 20, 2020 I've got a Schiit Wyrd on it's way, nothing but great reports for noise isolation and reclocking data. I'll report back. 1
Steffen Posted April 21, 2020 Posted April 21, 2020 On 20/04/2020 at 11:54 PM, 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. Expand Please do, I’d be very interested in your findings. 1
LuzArt Posted April 23, 2020 Author Posted April 23, 2020 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 Posted April 23, 2020 Posted April 23, 2020 On 23/04/2020 at 6:49 AM, 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 Expand 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. 1
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