Marsh headphone amp from Linear Audio

[RNMarsh]

Originally Posted by john curl

Go for it, Dick!

Hi John! I see you are back (?) in Berkeley land. I have been up in the foothills of the Sierra's - a stones throw from Nelson Pass - for the past 15 years. Cool, CA. Its a nice drive... come up and visit me.

[RNMarsh]

Here is an example of what I generally do -- I use two pcb ground plans: I have a seperate power ground on opposite pcb sides of +/- traces that form a strip-line for low z distribution. It never goes over signal traces and has a seperate path to the power source ground point.
The signal shield/ground is only over the signal area/wiring. Never crosses over power wires/traces or signal ground plane areas.
Separated power and signal returns are an important part of the high-end pcb design. This keeps power filtered transient currents/ripple/rfi et al out of the signal paths (via common). Result? Greater sonic clarity and seperation. -RNM

[RNMarsh]

example using old pcb circuit - green color are the two seperate ground planes: signal and power.
right side is power and left or center is signal. Traces are above the ground planes in red. -RNM

[sonidos]

@ RNMarsh

Things just got a lot clearer in my head thanks to the last 2 posts. Beautiful.

[Unomas]

Thanks Mr. Marsh, that is a great (though not a new one as you say!) rule to start dealing with ground. In my old days of circuits designer I had to deal with some very tough ground issues and keeping both power and signal GNDs well isolated and controlled in PCB routing was very helpful indeed. The magic rule is to avoid power ground current to interfere with signal ground as much as possible.

Another good rule is forgetting about the "magic" theoretical GND that could deal with everything with zero impedance! Always try imagine current paths in GND (following the least impedance route) to come back to source point and, in case you observe a conflict and/or interference with weak signals, try other route to avoid it.

Well we could continue with this issue for a long time but I think is better to point out that there are some very helpful resources for those interested. A good starting point may be:

- "Staying Well Grounded" H. Zumbahlen - Analog Dialog 2012-06 (Analog Devices Inc)
Here you can find a good deal of information and, what is even more important, a very helpful list of references on the Grounding subject.

Javier

[jackinnj]

One ground plane -- the Node "0" routing is shown in cyan and can be attached to the ground plane (which would make the copper pour "cyan").



I have a couple of prototype boards to dispense of, free for the shipping -- all soldered up etc., etc. Anyone interested drop me a PM.

[rjm]

Originally Posted by RNMarsh

example using old pcb circuit - green color are the two seperate ground planes: signal and power.
right side is power and left or center is signal. Traces are above the ground planes in red. -RNM

Where does the signal ground plane connect to the power ground plane?

[RNMarsh]

At the power supply common - usually the center tap of the power transformer. You use a seperate wire for that. Then, both power ground and signal ground planes/shields go back to same point.

[RNMarsh]

Like this shown -->

[jackinnj]

Anything objectionable about this: