Wow!
Offline
Michigan
Did I miss it, or where did you write what you did about the separate ground planes?
Offline
Texas
Jazzmarazz wrote:
Did I miss it, or where did you write what you did about the separate ground planes?
I think I rambled about it but didn't mention the current solution. I basically kept them separate. The digital side has both ground and power planes and the analog section has separate ground traces. After I thought about it, there was really no other way to do it because the transformer is doing both noise rejection and isolation and you can't do that with sharing a plane on both sides of the tranny. Given that, it also made no sense to connect digital and analog grounds together. Just in case, I used plastic connectors for the analog side, should the case ever be grounded to the digital count (e.g. if wanting to attach the voltage regulator to the side of the case to help with heat).
So, in short, you can think of the digital and analog section as entirely separate - they just happen to be in the same box.
Offline
Sweeeeeeden
I don't know if you ever figured this out, but Eagle allows you to explicitly define different grounds. Use add, then look under supply1 or supply2, and select for example GNDA for everything on the analog side. What this does is just to allow you to complete the board without having an airwire hanging, but it's the right thing to do.
Offline
Texas
If you pulled up the board layout, that airwire is actually the PE connections for the DIN jacks. They are just the stress joints and I didn't see a need to tie them to ground, so I didn't.
I did go back and forth on using a ground plane versus traces on the analog section though. Since it was basically point to point in each side of the tranny, I didn't see much value in a plane there. Doing it that way also helped keep the analog wires further away from the digital section.