SW Headphone Distribution Mixers

I've designed an API style summing mixer to use for the headphone distribution system at my new studio. Basically it's a 10 channel mixer (8 mono, 1 stereo) with summing and line amps based on 2520 discreet opamps. There's also an option to use a DIP8 opamp in the mono channels. I owe a lot to Jeff at Classic API, Hakanai for the STEREOTYPE board which got me interested in this, and everybody else who has covered this territory well on this board.

Since this is the first PCB I've ever laid out I'm hoping some of you would quickly glance at it and tell me if there are any obvious errors. I've tried etching boards before and only failed so this time I think I'm going to skip right to having a prototype manufactured, and any tips you could give would be greatly appreciated.

Also, if anyone else is interested in this project please let me know, I'd be happy to order additional boards.

Thanks for looking!

Here are the links: I made some pretty significant changes to the layout on 8/28 which are represented in V2
SWMixerBoardV2.png
SWMixerSchematicV1.png
SWMixerBOM.xls

Totally new version below ->

Nice project.

On quick glance on the PCB ( Coming from a non PCB designer tough)

- Some of your top tracks are a little too close from other pads/Vias if you take a closer look.
- Some Tracks doesn't seem to be connected on Bottom side, or unfinished? Hard to see tough
- I would probably make the Ground plane have more clearance with the tracks, you can do this in Eagle on the "isolate" option when choosing Polygon for the GND Plane.
- Maybe having the Ground pads on  better thermals would be easier to solder.
You'll find the different Thermal pads options when using "polygon" tool also. The best is the one made as a Cross and not the pad tottaly connected to the GND plane.
And you can make the Thermal Pads and so the cross on the pad more "open" so it will even be easier to solder on it, you do this in DRC setup,
and choosing  "supply", There you'll find "thermal" and it's isolation in "Mil".

For the changes to take effect you need to redo the GND plane each time IIRC (maybe there is an easier way of refreshing actually?)

But all in all it's a nice achievement for a first PCB, and some hours you've put to make it happen, good luck to you....

Thanks for the tips! Yeah, as I said I'm new at this so anything at all would be helpful. I've adjusted the pcb to take into account your suggestions. Anybody see anything else?

Okay, I went back to the drawing board on this. I made a mock up pcb for just a few input channels today and it worked great.

The big changes from the original version are that I decided to go with THAT1243 for the input sections instead of fully discreet. I finally decided that was going too far even for myself. Also I added a headphone amplifier based on the SDS design that's floating around the interwebs. And finally I added a headphone mute switch wired stereo/left only/mute.

After changing the channel faders to 10k the LCR panning switches got a little funky, so I changed the center channel resistance to 69.8k. That seemed to do that trick.

My big question at this point is: Is it going to be safe to send the DC voltages down the same snake as the audio? I plan on tying two wires together for each of the + and - lines. However I've heard that can be dangerous due to heat if one of the connections comes undone at some point. Anybody with more experience on the power-runs side have a thought? Thanks in advance.