JBL creature touch volume not working when not grounded

[gkmaia]

I have one of these JBL creature

And the  touch buttons only work if it is connected to a device that has EARTH/GROUND.

The Creature's SMPS wall socket side has just the line and neutral, no EARTH.

If I connect it to my TV that has only line and neutral volume does not work. If I connect it to my keyboard that has an earth at the wall socket the volume works.

Also interestingly... if I touch the negative terminal of the audio input plug and touch the volume it works.

Could someone explain the reason why earth is required? Is there a work around it or it is a natural limitation of this product?

Is it silly to add a 3 pin socket to the primary side of the SMPS and connect the ground to the negative terminal of the secondary side. Similar as when you ground the negative rail?

[Kaluluka]

Hi!
I know , this is a bit old posting , but anyway:
Do you use original JBL power supply for it?
I ask because: Original Power supply provides AC 18 Volts , not DC!

Regards,

[Cyberdragon]

It's probably a capacitive touch sensor relying on a ground reference. If the machine is not grounded when you touch it, it will just remain floating and have no potential difference to trigger the sensor. (you also create a potential by connecting yourself to the DC common point). If it's just a 2 pin AC transformer, it'll be relying on something like inter-winding capacitance (or have some sort of Y cap across it, unsure, haven't had one of these to examine).

Other capacitive touch sensors such as those for screens get around this by referencing to themselves through creating a tiny AC field feeding back on itself that gets disturbed when contacted, and can electronically filter out anything not a finger or stylus that recreates that feild distortion, basically like a metal detector except with capacitance instead of inductance.