Prickling sensation when touching WiiM Amp

[blaha]

Hi,

With two of my four WiiM Amp I've noticed that, when touching the case, there seems to be some level of electric current present on the metal casing.

It e.g. prickles at the fingertips when moving them across the case. This sensation is stronger in the back half, but also present in the front.

This is not a static discharge, but constantly present as long as the amplifier is plugged in. It disappears when unplugging it. No change when turning the plug around.

Is that common and, most importantly, safe?

 

[Wiimer]

Hi,

With two of my four WiiM Amp I've noticed that, when touching the case, there seems to be some level of electric current present on the metal casing.

It e.g. prickles at the fingertips when moving them across the case. This sensation is stronger in the back half, but also present in the front.

This is not a static discharge, but constantly present as long as the amplifier is plugged in. It disappears when unplugging it. No change when turning the plug around.

Is that common and, most importantly, safe?

Please try to find out the PCB version of your device here.

WiiM Amp

When I listen to streaming music, the volume level is 80% to reach the same sound level. The amps output volume changes with the tv volume level, so I don't seem to be able to raise the TV output independently to increase the gain. I tried optical as well with same low level output requiring...

forum.wiimhome.com

Also, contact support to discuss a replacement.

 

[blaha]

PCB Version is 5, for all four of them.
Replacing crossed my mind, but considering that it affects two of them (and actually the two I got last), I figured I'd inquire first if that's maybe just normal. Anyone else experiencing this?

 

[Wiimer]

PCB Version is 5, for all four of them.
Replacing crossed my mind, but considering that it affects two of them (and actually the two I got last), I figured I'd inquire first if that's maybe just normal. Anyone else experiencing this?

My WiiM amp is also PCB 5, but I don't have such a problem.

 

[jxrxme]

I don’t habe this with my Amp. But I know this sensation from all MacBooks I ever owned while connected to a charger that has/uses a cable without grounding (like the Amp has).
I wouldn’t worry.

 

[Valdo]

I don’t habe this with my Amp. But I know this sensation from all MacBooks I ever owned while connected to a charger that has/uses a cable without grounding (like the Amp has).
I wouldn’t worry.

Funny side note.
Every night while scratching my wife's back (unique situation right) i can feel that "Prickling sensation" when she plugs in her iphone-charger while doom scrolling.

 

[blaha]

Regarding the MacBook comparison: Good one. However, the WiiM Amp has mains power going in, a MacBook does not - means the potential worst-case is quite different.

Regarding cables: This also happens without anything being connected (well, apart from power, of course).

Yet again: Two Amps have it, two don't. Means it's probably not me, but if it's an actual issue, then probably others will experience it, too.
However, the two affected units are from the same order... maybe a bad batch? All four are the same PCB version though.

 

[Petevid]

Try swapping the amps around to see whether its a location/system earthing based issue.

 

[blaha]

Already tried different locations; considering that the power cable doesn't have a wire for earthing and the Amp itself has rubber feet, that's unlikely to change anything. Will still try a 1:1 swap of the units later today and see if/how that changes anything.

 

[harkpabst]

Already tried different locations; considering that the power cable doesn't have a wire for earthing and the Amp itself has rubber feet, that's unlikely to change anything. Will still try a 1:1 swap of the units later today and see if/how that changes anything.

If you can take one of the "non-prickling" units (just the raw device, all cables and connections as before), put it exactly in place of one of the "prickling" units and it still doesn't start to exhibit the prickling behavior, then I would return those two units as faulty.

Just my two cents. Euro cents, to be exact.

 

[blaha]

I've swapped positions of one prickling unit with a non-prickling one.

Observations:

- As soon as HDMI is connected to my TV, the prickling stops, no matter which unit.
- After swapping, the previously "good" unit also some prickling - but much less than the "bad" ones. (direct comparison with only power connected, same outlet)
- Location/room/outlet seem to have no influence.

At some point the prickling got significantly less, but returned later. No obvious reason.

By the way, I've noticed that there prickling sensation is especially present when sliding three fingers along the corners and left/right sides of the Amp. It then feels like the surface is vibrating on every move of your fingers.

Maybe some of you would treat that, with HDMI unplugged?

Thanks!

 

[blaha]

Just tested once more:

- Myself standing on the floor (any room, tile or carpet), especially with bare feet: prickling.

- Plugging in HDMI to TV: prickling stops.

- Detaching myself from the ground (e.g. small ladder with plastic steps): prickling stops.

This is identical behavior for all four of my units now.

Still wondering if this is safe though (especially because connecting HDMI seems to ground it).

 

[onlyoneme]

The Amp is not earth grounded with the power cord, so sometimes you act as a ground point when touching the chassis. As a result you can experience the current flow.

 

[Petevid]

So it seems like it’s an earthing issue in your set ups. With the HDMI connection I guess the earth connection is being picked up through the HDMI cable from your tv.

 

[blaha]

The Amp is not earth grounded with the power cord, so sometimes you act as a ground point when touching the chassis. As a result you can experience the current flow.

Yes, that's quite obvious. Question being: safe or not?

Regarding earthing issue: well, by default there's no earthing on the WiiM Amp, so there's not really anything to be done incorrectly there.

 

[WiiM Support]

Just tested once more:

- Myself standing on the floor (any room, tile or carpet), especially with bare feet: prickling.

- Plugging in HDMI to TV: prickling stops.

- Detaching myself from the ground (e.g. small ladder with plastic steps): prickling stops.

This is identical behavior for all four of my units now.

Still wondering if this is safe though (especially because connecting HDMI seems to ground it).

Hi blaha,

Based on insights from Petevid and onlyoneme, it seems to be a grounding issue with your setup. I'm escalating this to our Engineering team and will update you soon.

 

[blaha]

Hi blaha,

Based on insights from Petevid and onlyoneme, it seems to be a grounding issue with your setup. I'm escalating this to our Engineering team and will update you soon.

Thanks; just to emphasize: this can't really be caused by my setup, because the Amp itself uses a two-wired power cable and simply has no ground wire.

Connecting HDMI seems to indeed ground the casing.

So I'd say, either this is just perfectly safe and normal, or the lack of the Amp's grounding is a design flaw.

FYI: I also have a ticket open, so the engineering might already be aware.

 

[WiiM Support]

Thanks; just to emphasize: this can't really be caused by my setup, because the Amp itself uses a two-wired power cable and simply has no ground wire.

Connecting HDMI seems to indeed ground the casing.

So I'd say, either this is just perfectly safe and normal, or the lack of the Amp's grounding is a design flaw.

FYI: I also have a ticket open, so the engineering might already be aware.

Hi blaha,

You're correct. The WiiM Amp's casing isn't directly grounded but uses capacitive coupling to achieve grounding—a standard approach to minimize electromagnetic interference and meet regulatory standards. When you touch the casing while also in contact with the ground, you become part of the circuit, leading to the sensation you've noticed.

This isn't a design flaw. We've implemented rigorous safety measures, and the device has passed all necessary safety certifications (based on IEC 62368-1 safety requirements), ensuring that the sensation is completely safe, albeit potentially irritating. This phenomenon is more common in 220V systems, typical in Europe and Asia, than in the 110V systems used in North America.

 

[Mr Ee]

Indeed - I'd hardly say the 2 core 'figure eight' power connection is a design flaw, it's practically ubiquitous.
Plugging in another cable, such as hdmi or rcas, can complete the grounding, as can you!

Simple solutiion - don't stroke the amp

 

[blaha]

sign flaw. We've implemented rigorous safety measures, and the device has passed all necessary safety certifications (based on IEC 62368-1 safety requirements), ensuring that the sensation is completely safe, albeit potentially irritating. This phenomenon is more common in 220V systems, typical in Europe and Asia, than in the 110V systems used in North America.

Appreciate the explanation! And my apologies, I did not mean to presume it being a design flaw, but to emphasize that all units behave consistently, meaning it being normal (or not) for all units and not related to a fault in the setup.

Regarding "as can you" - well, for most of my Amps I'm just playing music on some bookshelf speakers, using a WiFi source, so there's nothing nearby to connect to.

However, as long as it's indeed safe and normal, this doesn't bother me.
Thanks also to support for pointing out that it indeed _is_ both safe and normal.