USB Isolator ADUM4160 for Ground Loop Hum

[KingBubba]

A year or so back, I bought a 2 bay hard drive dock that I attach to my laptop and I store videos and music on. The idea was a good one except for one thing: a ground loop. As soon as I unplug the power from the unit, all is quiet. The plug is two pronged and un-keyed. I have tried reversing it to no avail.The manufacturer, StarTech, was very prompt in responding to my inquiries, but were unable to come up with any fixes or ideas. Except for this ground issue, these docks are great and with a program like Acronis, give you a lot of HDD flexibility.

I did some online research and came up with info regarding devices based on the ADUM4160 chip. The following link to a forum gives some opinions to the positive.
https://www.head-fi.org/f/threads/usb-isolators-based-on-adum4160.806190/

It made me decide to try one of these cheap, $11.39, isolators. If anyone here has had any experience with these, or any isolators based on the ADUM4160 chip, Let me know what you think. I'll give a review when this thing arrives from Hong Kong in three weeks or so.

 

[Poinzy]

I think USB isolators can cause bandwidth problems, sometimes serious ones, which is why they aren't terribly popular de-noising solutions.

 

[KingBubba]

I would prefer not to have this solution interfere with the audio, but I thought it worth a try. I have read both good and bad online; so it is a crapshoot. Thanks for the comment.

 

[Poinzy]

No problem.

You never see what I would call credible audio outfits making USB isolators -- Radial, Ebtech, Samson. They make isolation gear, but for audio lines and, in the case of Ebtech, standard power lines. Nothing else.

 

[KingBubba]

The isolator arrived today and it was a waste of $12. Live and learn. It did not reduced the ground loop even part way.

 

[recordgeek]

As a first test, I would put the dock on an extension cord and run it to a different electrical circuit.

If you have a map of your electrical circuits, try a few different receptacles that are on known different circuits, and on a different leg from the laptop.

Many variables but I would look at resolving this as an electrical issue.

 

[KingBubba]

Swapping to another outlet is worth a try. I'll run it to the outlets in the kitchen. The device PS has a two prong plug so grounding is not possible. The other possibility is that the issue is RF induced, but I tried a usb cable with ferrite cores on it and it made no difference.

 

[KingBubba]

I'll give it a try some point in the future. I had considered that a good while back, but I negated my own thoughts as I sometimes do. Thanks.

 

[gvl]

Given there is no grounding pin on the plug I would think the classic ground loop is impossible as there is no grounding conductor to complete the loop. Grounding the chassis may in fact introduce the loop. I doubt switching outlets is going to help. What kind of loop noise is it? Low frequency hum or buzzing digital kind of noise? Do you have an external DAC or the speakers are connected to the laptop or perhaps these are the built-in laptop speakers?

 

[KingBubba]

My laptop is connected to my bedroom system via a usb sound card and mini plug adapter to RCAs. This is a standard 60hz ground loop hum. The ground in the usb cable would be the connection for the ground loop. This is why I was hoping the isolator would help. I have two system that I set up this way. The living room is the other system and the hum there is way more pronounced than the bedroom system. The hum stops as soon as I unplug the hard drive dock from the wall. The hard drives in the dock do not have to be turned on for the ground loop to be present. I am now bypassing the whole mess by putting 2tb hard drives in the 2nd HD adapter in the thinkpads. I will now just use the dock for backups and cloning drives. I'll keep a copy of my videos and music on the new 2tb hard drives.

 

[gvl]

With just the ground wire in USB cable there is no loop. Loop is when both ends are also grounded so the loop is formed:

Source ---- usb --------- Destination
I______eq. ground______|

You don't have the equipment ground connection so there is no loop. The likely cause is the noisy power supply in the dock that somehow ends up as ripple on your mobo USB power lines powering the usb Sound Card, if the PSU external you can try a different one.