Oh yes,the 1st idea worked a lot. the noise was damped many times.
Thanks..
Looking forward for more suggestions.
For the input:
omit the 10kOhm's (2 on the left side).
a 47kOhm, a 0.1uF and a 50k pot in series with the audio out from mp3 player and the input is taken from the center leg of the pot.
2 such things for L and R.
the power supply and audio input, output, all have a common ground.
The power supply:
(Vs) is 9VDC (12v, 100uf filter cap regulated by a 9v 1A regulator)
a switch for on off, and a switch to switch from battery to mains supply.
N.B. I haven't created the final schematic yet. I did all the things directly on the pcb artwork.( the initial one has been posted).
**broken link removed**