[proid]

I etched a portable amp pcb, star ground point at common point of two 9v batteries but i route wrong two channel 

Then i do another board which i think has better ground (more dedicated ground traces), star ground at one leg of the filter capacitor:

But it actually sound worse, the first version is clearer, sound more open and effortless so i wonder if that is the problem of grounding? because everything else is exactly the same. I made new eagle board, does this look any better?

 

[gootee]

It would help if you would provide more information, including a schematic and better labeling of what's on the PCB.

 

[holland]

Heh, you're building a half-baked O2.  You know, you could just copy the layout.
 
I would take a line from the split supply and feed it into the ground plane.  I would take the smoothing capacitors and connect it to the ground plane directly.  I would place the plane directly into the headphone jack (IN) ground.  I would also take the volume jack and connect it to the ground plane.  The ground plane would be large.  I would take a thick line from the headphone (OUT) ground, separate from the ground plane and feed it directly back to the battery mid-point.

 

[proid]

Quote:

Heh, you're building a half-baked O2.  You know, you could just copy the layout.
 
I would take a line from the split supply and feed it into the ground plane.  I would take the smoothing capacitors and connect it to the ground plane directly.  I would place the plane directly into the headphone jack (IN) ground.  I would also take the volume jack and connect it to the ground plane.  The ground plane would be large.  I would take a thick line from the headphone (OUT) ground, separate from the ground plane and feed it directly back to the battery mid-point.

Yes, it's a mini O2, can you explain why you suggest to ground like that? In fact i build all 3 version and ver1 sound much better than both ver2 or ver3

 

[holland]

Quote:

Yes, it's a mini O2, can you explain why you suggest to ground like that? In fact i build all 3 version and ver1 sound much better than both ver2 or ver3

 
Keep the return currents from the headphone away from the amplification circuitry, and the input source, and feed it to the "battery source" to sink the currents immediately.  You could also make the ground plane smaller and use smaller slices to feed the opamps, same idea about "isolation".  A larger "well" for the input side.  I'm not sure if NwAvGuy did it that way, you can look at his docs.  I believe it has pictures of the ground planes.
 
Edit: Also, star ground.  I wouldn't use it for a PCB.  For point to point wiring, yes.  In star ground, you have nodes of ground potential.  The same idea.  For PCB, you use planes.  Your first version looks better, but you need a bigger "wire" to return.  You also didn't have power caps in the first one, and you should tie the input ground directly to the plane with the volume knob.  It would probably be better to move the input jack next to the pot.  It'll require a different layout.

 

[proid]

Quote:

 
Keep the return currents from the headphone away from the amplification circuitry, and the input source, and feed it to the "battery source" to sink the currents immediately.  You could also make the ground plane smaller and use smaller slices to feed the opamps, same idea about "isolation".  A larger "well" for the input side.  I'm not sure if NwAvGuy did it that way, you can look at his docs.  I believe it has pictures of the ground planes.
 
Edit: Also, star ground.  I wouldn't use it for a PCB.  For point to point wiring, yes.  In star ground, you have nodes of ground potential.  The same idea.  For PCB, you use planes.  Your first version looks better, but you need a bigger "wire" to return.  You also didn't have power caps in the first one, and you should tie the input ground directly to the plane with the volume knob.  It would probably be better to move the input jack next to the pot.  It'll require a different layout.

Thanks a lot for your suggestion! I redraw the board, swap the input and output jack, connect input ground to ground plane with the volume, make output ground bigger and all ground trace tie to common battery ground.

Or should i just make a ground plane?

 

[holland]

Just so you know, I'm far from an expert and don't have the setup to build and measure the noise here.
 
I would split #2.  I would put the caps on the plane and use the plane as the star node for the opamps (traces out).  I would feed the headphone return, on a separate trace, to the battery.  So, you would have 2 nodes on your star.  The plane is one, and the battery is the other.