I'm sorry to hear that you're having trouble controlling the volume.
The 3.5mm jack is a fixed audio out input, rather than a headphone jack, and isn't controlled by the volume controls on the TV. So the external speakers will require an amp for the volume control.
I have a UA46B8000 LED TV with a 3.5mm headphone jack and a 2.1 speaker system with its own power supply.
The system works great, but I am unable to control the volume using the tv remote controls.
Any ideas on how can I control the speakers volume without buying an amp?
Thanks for your replies!