Ground loop fun

[Chris Prosser]

Hi Folks,

Love the forum. I've been finding myself loving the mixture of helpfulness and measurement, reading late into the night.

So I want to talk about ground loops, and not this kind of ground loop

I've been struggling with noise on my laptop system for years. I could largely ignore it because if I moved the cables (aka antenna) just right, it wouldn't bother me. But I just picked up a Topping D10 and the display on it kicks out a ton of noise. On the plus side, it was loud enough that it made troubleshooting possible. After much unplugging of stuff I isolated the ground loop as going from my ungrounded laptop, through the mini-displayport cable to my grounded monitor on one side, and then via usb to my grounded audio equipment on the other. My old DAC that I was hoping to retire (a Grant Fidelity TubeDAC-11) has TosLink, and so does my laptop, so $6 later and a new piece of fiber and that actually fixes it for the first time in years!

But...new gear!

It looks like I need to get a USB Isolator to block the ground loop to use the D10. I'm not terribly against the idea as I do electronics and have a USB mixed dso that I always use hunched over my laptop not plugged into anything to avoid this exact problem. My back would really prefer my external monitor .

It looks like they all use a similar Analog Devices chips. Any suggestions on what to look for?

Cheers,
Chris

 

[rvsixer]

Thankfully I did not have a ground loop in my RV-6.

 

[amirm]

The Intona will provide isolation but at high cost (https://www.audiosciencereview.com/...s-of-intona-usb-isolator-for-audio-dacs.2616/).

Now, why did that single engine plane turn so fast at the end? Was it on demand or unexpected?

 

[RayDunzl]

Unintentional

http://www.ladieslovetaildraggers.com/blog/taildraggers-vs-tricylcle-gears/

Ever ride a tricycle backwards?

 

[Soniclife]

I have a olimex usb-iso (usb 1 only) that worked when I had this problem.

Are the topping products very sensitive to this problem?

 

[Chris Prosser]

That Olimex looks right up my alley. Also fits my style of crappy aesthetics .

I don't think Topping products are particularly sensitive to this problem. In my case the D10 gives off some noise that fit my antenna tuning perfectly. But previously I could hear a specific subsystem in my laptop turn on, so my ground loop was particularly bad for computerish noise. I didn't actually hear any 60 cycle hum, which made troubleshooting it harder.

 

[amirm]

I ordered this Esky filter for a whopping $6 from Amazon to test: https://smile.amazon.com/gp/product/B00ZWOQLFM/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

[RayDunzl]

I ordered this

That's different, a filter for signal to the headphone.

 

[Rod]

Would this be any benefit to the RME dac/amp

 

[Chris Prosser]

RME?

That’s quite a nice isolating transformer you have there. When I was learning to use my analog scope, I was poking at a motor wanting to look at the waveform and accidentally did a dead short to ground. That was terrifying.

In my case that would help, provided I put it in the right place. If I just floated the ground of all my audio equipment, I would still have a ground loop. But if I dereferenced the voltage of just my amp or monitor it would fix it too.

It makes me wonder if everyone who claims USB sounds worse than an optical connection actually has an undiagnosed ground loop.

 

[Rod]

RME ADI-2 dac/amp.
I have a 60 watt per channel tube amp that I gave up on finding the hum. I tried ground loop isolators, the above isolating transformer, cut the ground off an extension cord, different circuits at the house, even called the utility company to see if there was grounding problems. Took it to a repair center and at there place of business there was no hum. Finally gave up chasing it. I was at the limits of my knowledge. I also live in a small rural town so no one out here would have the knowledge to do it either. I hooked up my Denon amp and used that instead.

 

[DonH56]

My guess is the house safety ground was not properly connected.

 

[Rod]

My guess is the house safety ground was not properly connected.

Thanks for the suggestion. I did call the utility company and the guy who showed up understood the hum in a tube amp problem, he was familiar with tube amps, but could find no grounding problems. But yes it is a problem in the house somewhere and a utility company man isn't going to spend the time besides what he has to for safety.

 

[Rod]

But he told me that he was empathetic. Must be a audiophile. I thought I seen his eyes watering up when I told him it was ruining my listening experience. He did try what he could with the time allotted.

 

[pirad]

As a test try powering it from a UPS.
Make sure it’s unplugged.
It is strange that the isolating transformer
did not work .

 

[Chris Prosser]

And just to tie things off, the olimex usb-iso worked wonderfully to solve my ground loop. I had to scrounge out a wall wart from my box of wall warts as the Olimex only can handle 375mA and the Topping needs 500mA. But with that hooked up, it is blissfully silent for the first time since I bought this laptop in 2013!

 

[weikagen]

I ordered this Esky filter for a whopping $6 from Amazon to test: https://smile.amazon.com/gp/product/B00ZWOQLFM/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

View attachment 12419

It's most likely a double 1:1 600 ohm isolation transformer for each channel, like in this video:

Some people make their own too:

Curious to see if there are any low/high frequency roll offs using that in your measurements