vibration/electric current/shock when touching audio device chassis

[Ziroz]

I have used a Fiio K5pro as a usb dac for my pc and never had any issues, nothing funny when using and touching the device.
After recently upgrading and moving the unit to my reading desk, I found there is quit a significant feeling of vibration/electric current/shock when touching the case, the electric current is especially noticeable when I stand on the floor bearfooted. And when I reconnect the device to my pc with a usb cable, the electric current immediatly went away.
I have also experienced this with a SMSL A300 amp which uses a 3-prong plug but uses a floating ground inside the device (the ground pin is not connected to anything inside). After reaching out to SMSL, they said it is purposely designed this way (i.e. with floating ground) to avoid ground loops and this is not an issue.
Other members have reported the same happening with Topping DX3 Pro+ which uses a external dc power supply like my K5pro.
I tried this with my new E70 & L70 stack and there is no issue, they use 3-prong plus and I presume the ground is not floating.
Here's my question:
1. Is this a grounding issue?
2. Would you consider this a defect?
3. Is there any other way to solve this without usb connection?

 

[solderdude]

I have used a Fiio K5pro as a usb dac for my pc and never had any issues, nothing funny when using and touching the device.
After recently upgrading and moving the unit to my reading desk, I found there is quit a significant feeling of vibration/electric current/shock when touching the case, the electric current is especially noticeable when I stand on the floor bearfooted. And when I reconnect the device to my pc with a usb cable, the electric current immediatly went away.
I have also experienced this with a SMSL A300 amp which uses a 3-prong plug but uses a floating ground inside the device (the ground pin is not connected to anything inside). After reaching out to SMSL, they said it is purposely designed this way (i.e. with floating ground) to avoid ground loops and this is not an issue.
Other members have reported the same happening with Topping DX3 Pro+ which uses a external dc power supply like my K5pro.
I tried this with my new E70 & L70 stack and there is no issue, they use 3-prong plus and I presume the ground is not floating.
Here's my question:
1. Is this a grounding issue?

Yes,

2. Would you consider this a defect?

unlikely. It is more likely to be a lack of safety ground.

3. Is there any other way to solve this without usb connection?

The metal parts that can be touched must be grounded. This you can do using central heating or all copper water piping or using the 3rd prong of a mains socket. Assuming the 3rd prong is actually connected. Simply put a wire below one of the screws and connect that to a (safety) ground.
This action might cause some hum to be heard.

 

[MaxwellsEq]

@solderdude is right - you are feeling an induced current due to the metal parts not being earthed. A friend had the same feeling when he touched his washing machine. I checked and found it was plugged into a wall socket that did not have a safety earth! I was astonished.

 

[Spkrdctr]

Solderdude gave you great advice. Just hook up a grounding wire to you chassis/case. Since it is a very weak voltage/current even a small 20 or 22 gauge wire will work.