[Gman]

Hi guys,

I have attempted over the last couple of days to lay out a solid state(gasp!)headphone amp using ExpressPCB. It is a OPA627 with a BUF634 inside the loop(Jung multiloop style). I just wanted to get some learned opinions of the layout before I start to work on the regulated supply. I also layed out a Psuedo ground driver using a BUF634 to use with a 30v desktop power supply that I have but I'm not sure that it will ever see the light of day. I figure that if I'm going to pay for the boards I might as well do it right. Is there anyone out there that will post this image to the forum or let me send it to you for your opinion? It's too big to attach to this post. Thanks either way.

Gman

 

[morsel]

Shrink it to 600 pixels wide and you will be able to post it.

 

[Gman]

Good call Morsel. Thanks. Here's the image.

G

 

[jcx]

the quickest improvement to your layout would be to place power and circuit interconnect on same layer and fill in ground plane on other (component/top) layer, i would also add 0805 pads at all amp ps pins for lo inductance 0.1 uF bypass caps (if your prejudices allow for X7R ceramic in bypass application -- spend a couple of $ ea for 10 nF NPO if not)

this is the lazy approach, better layout would keep power pin currents out of feedback/input ground reference and you would want to look at minimizing power distribution loop area/mutual inductance with feedback loop

on such a small board at headphone current levels the ground plane approach will get you 95+% of the way there without much thought

on circuit topology, I would seek to limit RF/EMI with input RF filtering, explicit low pass amplifier characteristic, Zobel output network and PS RF filtering if using external (wall wart) power - presumably the fet input 627 is better than most in rejecting RF/EMI but it’s a nasty world out there!