TDA2009 input noise?

Hello,

This is my second shot on a chip amp, the first one was TDA2050 which worked really well. I have some simple pc speakers with a dead amp lying around and thought about doing this 2x10W simple amp. So i downloaded the datasheet, etched my pcb, soldered all the components and it came out pretty good. Definitely not one of my first diy projects, i've built a dozen guitar effect pedals :)

However, i noticed this strange behavior:
1. when i use an old short cable stripped from the dead amp, from the PC output directly soldered on the PCB i get amazing sound, no noise at all.
2. when i use a common 3.5mm audio cable (1.5m long) and solder it directly on the board, i get noticeable noise
3. when i use a jack to connect the audo cable, and then solder the jack to the PCB, i get some huge buzz/clapping sound, and as you can guess, no music at all. The TDA also overhears very fast, in about 2-3 seconds!
(There was no big heating at all in the other 2 cases)

So what could it be, is there anyway i can fix this?
Thank you for this great forum :)