• From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Topic: Babyface USB ground loop (mac mini)

There is no way around it. The ground hum only happens when the USB cable connects the mac mini to the RME. Using an external power supply will not disconnect the ground path from the computer (does it? it doesn't seem to)
Nothing else causes the hum.

Is there an RME approved ground lifter or solution for a USB cable? It seems as if the choice of having a Mac Mini and an RME babyface is being resigned to a ground loop.

Is that the case?

If so, I just need to get used to it now.

cheers y'all

ricknance's Website

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,784

Re: Babyface USB ground loop (mac mini)

Not a known general issue, really. What else is the BF connected to?

Regards
Daniel Fuchs
RME

RME Support's Website

  • From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Re: Babyface USB ground loop (mac mini)

That's pretty much it. There's a mac mini and the powered monitors (balanced lines). Everything is on the same power point. The headphones don't hum.
The computer is connected to an SSD, a mouse, and a vid monitor. In the past it has been connected to an external jbod, which did add to the problem.

If it's not a known issue then I expect there's nothing on the RME end. It's a Babyface original so it would have come up before now.

But while I'm here, just to say, this and my old Multiface are without a doubt the best digital gear I've owned, bar none. I wish the problem were with the Babyface. It would get fixed.

Thanks,
Rick

ricknance's Website

4 Reply by MC

  • MC
  • MC
  • Administrator
  • Offline
  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,612

Re: Babyface USB ground loop (mac mini)

As the phones don't hum the obvious issue is the balanced connection to the powered monitors. This might be the seldom case where one needs to disconnect pin 1 in the XLR cable.

Using a galvanic USB isolator should work work as well, but is a much more expensive solution, and requires to use an external power supply for the BF.

Regards
Matthias Carstens
RME

MC's Website

  • From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Re: Babyface USB ground loop (mac mini)

I did try disconnecting pin 1 but it got worse.
I tried a simple version of a USB isolator, by insulating the power feeds from the USB cable (electrical tape over the pins) and used the external power supply. But then the RME wouldn't power up regardless. I thought that might be too simplistic a version, but worth a try.
I take it then, that the galvanic isolator is the next step. Any suggestions for one in particular? Or will they all be about the same?

Thanks

R

ricknance's Website

  • vinark
  • DAW Mastermind
  • Offline
  • Registered: 2009-06-05
  • Posts: 2,788

Re: Babyface USB ground loop (mac mini)

If you only connect USB and headphones, no other connections and no power supply you can not get a ground loop. How is that working?

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
BFpro fs, 2X HDSP9652 ADI-8AE, 2X HDSP9632
  • From: Seevetal
  • Registered: 2007-05-03
  • Posts: 409

Re: Babyface USB ground loop (mac mini)

Maybe the LEDmonitor is grounded

UFX+, FireFace 802 FS, Digiface USB
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  • From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Re: Babyface USB ground loop (mac mini)

Still happens with the monitor unplugged. There IS a slight change though.

ricknance's Website

9 Reply by ricknance (edited by ricknance 2022-08-21 17:05:01)

  • From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Re: Babyface USB ground loop (mac mini)

Solved: See following.

[s]
It looks like if I wait a month or 3 (?) HiFiMeDIY will have an isolator for under £50, so I guess I'll find out then.

(update) Just tried using a USB to spdif optical converter (ancient Edirol UA-1D) but no joy. Without the USB carrying the signal, the RME won't boot.

Some other people with Mac Minis doing audio are having the same issue. Finding a way to ground the Mac is the problem. Hoping that buying a grounded computer isn't the solution.[/s]

ricknance's Website

  • From: Leicester, Eng
  • Registered: 2011-10-23
  • Posts: 18

Re: Babyface USB ground loop (mac mini)

Solved!

Good hints about the monitor, cigame, but the problem was backwards.

The monitor was ungrounded, the Mac (mini) is ungrounded. So they were okay with each other., just not with everything else.

They both needed grounding to kill the loop(s) An HDMI cable will deliver a ground to the mac.
I put a fully grounded monitor in and _all_ background noise disappeared. If I get my ear up to the monitors I can hear a bit of hiss/hum, but I suspect that's the fridges and a fairly badly designed house electrical system.


Fortunately had an old 19"rgb monitor (and an rgb/hdmi adapter) in the attic. It's fuzzy. But better that for now than fuzz on the sound.

Conclusion: The Mac Mini is incompatible with ungrounded displays.

Thanks for all the input.

ricknance's Website