Isolating signal ground and power ground

[CurtisWCole]

This might seem like a dumb question. (After spending forever and a day learning about all kinds of pedal related techno-jargon, it does to me.) But I ran across a few problems people were having with noise from the two grounds mixing and just can't seem to get my head around it. Lets assume a few things.

1.) I can make a pcb from scratch so there isn't a limit (theoretically) on what can be done as far as incorporating new ideas.
2.) I know a little about star grounding and ground loops.
3.) I don't want the power switching or batteries.
4.) I don't want to "get away" with anything...it's just how I am.
Using these "parameters" ,if you will, what is the correct way to wire up a pedal without mixing the signal and power grounds.? I've read RG's comments about the "sewer ground" and if I'm doing my own layouts I don't want to have any issues with noises and ticks because of my ignorance. Would the negative lead from the power supply be the only "ground" to the pcb and the jacks only grounded to the pedal chassis? Or am I wrong? Now the same questions...but using plastic, pcb mounted jacks. Where does the sleeve pins go? Could I let the cables carry the signal ground?  (I told you it sounds dumb) But the more I think about it, the more baffled I get.
There seems to be some conflicting ideas for this. Or maybe I'm the conflict... What would be, in your well respected opinions, be the best or the optimal way to ground the effect and jacks?

Also, I want to thank everyone in the forum for sharing such great information with an idiot like me. I really do appreciate it!

Curtis

[Gurner]

Short of using isolation transformers/opto isolators etc - the signal ground & power ground need to meet at some point...the dilemna is where to allow them to 'join'.

Here's a 'one cold beer too many' journey analogy....your supply line is the 'traffic' source, your supply ground is the journey destination.....there are heavily used motorways which join the two together....but a motorway isn't an optimum place  to connect up your driveway from your house (hmm, perhaps this is getting too obtuse!), you are better joining your driveway (signal ground) on a much quieter road. The quietest road available is private 'sole use' road direct from your driveway to the destination (power ground). Therefore having one connection for your signal ground back to the power ground is gonna have the least amount of potential noise. That's essentially what star grounding is....lots of private roads driect to the destination (ground)

Ok enough analogies....you want your signal ground to avoid being in the same return path as known problem children (high current draw stuff - leds, coils etc).....current flows between your supply line & ground, so avoid connecting up signal ground near any of these type of paths to ground.

[PRR]

> without mixing the signal and power grounds?

In a simple transistor amplifier you need three circuits:

Input loop
Output loop
Power loop

To be loops, each needs two conductors.

Six in/out/power conductors total.

The transistor only has three legs.

Some loops must flow in the same conductor.

Usually:

signal input is Base to Emitter

signal output is Collector to Emitter

Power is Collector to Emitter.

Notice that Emitter (or any R-C network under it) is "common" to all three loops.

Frankly most pedals are _small_ ground problems compared to other electronics. Yes, IMHO you are over-thinking, or fearing the unknown. The MOST common problem is simply "forgetting" to connect a ground. Get them all globbed together any which way and you are doing well.

> issues with noises and ticks

In many designs the "ON" LED is by far the biggest current, and goes on/off abruptly. Think of LED current as a truck full of elephants. Pick a path for this truck. Do you route it through quiet residential streets with small children? Or shortest-possible route from zoo A to zoo B? Remember that wires are cheaper than highways and you can run a dedicated wire just for the elephant-truck or LED right back to the battery.

[CurtisWCole]

Thank you both for your responses. I also appreciate the metaphors.

I now see what you guys and others mean. Ultimately, I was just wanting everything to be "perfect" so I won't have to post a debugging thread later. It's just how I am.

Thanks again,

Curtis