Severe hiss on Line In - fluctuating to music

[galgogergo]

Dear all,

I've just bought myself a 2Box DrumIt 3 module. I've set it up properly, works and triggers mainly as expected.

I however tried to use the line-in jack with my phone.
As soon as I start any music on the phone, there's a SEVERE, horrible hiss starting out on the module through the headphones!

When I stop the music, the hiss is audible for one more second, and then it goes away. (as if the module shut it down). When I hit play, it comes back.
It also fluctuates to the volume of the music!
On the louder passages it increases together with the music; during the softer parts it quietens.

So irritating.

I use a plain 3.5 to 3.5 mm jack cable to the module, with a golden 6.3 to 3.5mm adapter on the end. I'm sure it's not the cable, since when it is plugged in the phone with nothing playing, it's dead quiet. As soon as I start playing anything, it adds the hiss to the music, with the same volume as the music is. It's really horrible.


Are there any reasons for this? How can it be stopped?

Thank you.
G