Computer Audio Asylum

RE: Ground loop blocker

23.242.178.78

emailtim

In Reply to: RE: Ground loop blocker posted by Ugly on February 17, 2021 at 11:13:22

DIY USB Y-cable to separate the data lines from the power lines.
Power supplied by a USB phone changer, data supplied by the PC.
There is probably a better way to do it.

Edits: 02/17/21 02/17/21

Follow Ups:

And not just for ground loops - AbeCollins 05:54:49 02/18/21 (3)
- Some DACs are entirely powered by USB drawing several hundred mA. Providing a separate 'clean' +5VDC may be beneficial.
- Some DAC USB receivers are powered by USB drawing significantly less power over USB.
- Some DAC USB receivers require USB power only to enable the DAC drawing a just a few mA.
- Some DACs require no USB power at all. In these DACs the USB receiver is powered by their own internal power supply as was the case with my Ayre QB9-DSD DAC.
As such, some USB DACs may benefit from spitting out the USB +5VDC with a Y-cable while others will see no benefit at all. To test whether the DAC requires +5VDC on USB at all, you can block the +5VDC pin on the USB-A connector on one end of the USB cable as I did.
- +5VDC over USB to DAC (Open in New Window)
Edits: 02/18/21 02/18/21
- RE: And not just for ground loops - emailtim 10:49:15 02/18/21 (2)
  Unfortunately, blocking the +5v doesn't get rid of the ground loop.
  It also has the side effect of making the DAC not function, especially when the user's manual clearly states it is powered via USB and has no other power input ports or battery packs. On second thought, it does get rid of the hum (and all other sounds). =)
  
  Edits: 02/18/21
  - RE: And not just for ground loops - Ugly 15:23:38 02/18/21 (0)
    "Unfortunately, blocking the +5v doesn't get rid of the ground loop."
    
    I think many people are using isolated 5V supplies, to simulate a host side connection, after cutting the power lines.
    
    But unless the data lines are also isolated, the ground loop with the pc, through the usb cable, hasn't been eliminated by using an isolated 5V supply like that.
    
    Perhaps if Amir wanted to do a video lessons on the type of equipment arrangements more or less likely to increase the strength of unwanted humming signals and other EMI, especially as it pertains to how people want to hook the gear up, even if he didn't have explanations for all his findings, at least there is something to talk about. I can understand the hesitancy to declare positive results without lab grade power for his equipment, etc. but I'm betting he'd probably help shed a little bit of light on the dark art of hooking stuff up correctly, for some people anyway.
  - RE: And not just for ground loops - AbeCollins 11:20:11 02/18/21 (0)
    I didn't suggest blocking +5v for getting rid of a ground loop. Was only suggesting that not all DACs even require the +5v, and an easy way to test it.
    I've never owned a DAC that created a ground loop as most modern DACs incorporate galvanic isolation over USB.
    
    Edits: 02/18/21
RE: Ground loop blocker - Ugly 12:23:57 02/17/21 (0)
I see. I am not saying I know what the answer is, but I thought Amirs comment about $0.03 cents worth of components to stop this problem which would presumably be very measurable was pretty funny and it made me laugh...ie detecting the presence or absence of hum signal.

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