I would go ahed wth the shielded wire for input.
I would check again grounding, can be a cold joint that makes the buzz.
C11 increased and nose decreased means that the amp picks the noise up.
You can se C11 up to 330 pF , thats the highest i would use.
Other than that, please install a potmeter.
If You use the computers volume controll, then it will produce a lot of noise.
The computer's analouge output has some noise in it.
If You turn the volume down by software, the noise remains at the same level, and some of the music is added, and all this amplified by the amplifier.
But, if You use a pot, and turn the sound level up on the computer, then the same amount of noise will be mixed with a -probably close to- a magnitude larger signal , and all this will be turned down by the pot.
So the signal to noise ratio is different in this case.
This is going to supress the noise to verry near inaudible at a healthy loud volume.
I would check again grounding, can be a cold joint that makes the buzz.
C11 increased and nose decreased means that the amp picks the noise up.
You can se C11 up to 330 pF , thats the highest i would use.
Other than that, please install a potmeter.
If You use the computers volume controll, then it will produce a lot of noise.
The computer's analouge output has some noise in it.
If You turn the volume down by software, the noise remains at the same level, and some of the music is added, and all this amplified by the amplifier.
But, if You use a pot, and turn the sound level up on the computer, then the same amount of noise will be mixed with a -probably close to- a magnitude larger signal , and all this will be turned down by the pot.
So the signal to noise ratio is different in this case.
This is going to supress the noise to verry near inaudible at a healthy loud volume.