im confused about dc- and grounds

[sjaltenb]

OK something I have been very confused about for a long time, and it will probably sound like a really dumb question but whatever.

On a typical stompbox wiring, you ground the center pin (dc-) jack to the sleeve or ring on the input or output jack, which is then grounded to the enclosure. Then, typically, your board is grounded to the same place. So your DC negative and board grounds are all wired back to the enclosure, basically.

So, my question....When I build a GGG ultra clean power supply, and it has + and - outputs....if I am not using this power supply in a typical fashion, where there will be output jacks....I just want to provide DC 9V+ hardwired to 1-2 circuit boards, (in a multifx board)...Do I just wire the - on the power supply to my enclosure, or star ground??

If that is the case, can I do the following: For circuits that have like 2-3 ground points (like a boss pedal), Can I wire those grounds to the - side of the ultraclean power, and then also run a wire from the negative output on the UltraClean to the star ground? Thus making my wiring a little neater?

Heres a pic of the GGG wiring:


Thanks!

[sjaltenb]

SO it would look something like this::



With the black wire obviously being the circuit boards ground point.

[R.G.]

You're all tangled up - as is very common - with terminology.

On a typical stompbox wiring, you ground the center pin (dc-) jack to the sleeve or ring on the input or output jack, which is then grounded to the enclosure. Then, typically, your board is grounded to the same place. So your DC negative and board grounds are all wired back to the enclosure, basically.

Kind of. This is another of those things like putting the negative wire on the center conductor in a Boss-style jack that we can't ever get rid of. Using the input jack of the effect to switch power is a bad idea that we mostly get away with because stompboxes are usually small and compact.

"Ground" means "a place that we've decided is going to be at 0.00000V by convention, and we'll measure all other voltages against that point." In the typical stompbox setup, where is ground? Is it the lug on the input jack? The sleeve of the plug? The enclosure of the effect, which is connected to the jack bushing? Or maybe on the circuit board? How about at the power supply? Here's a rule to help you decide - all wires are really low-value resistors, and so any two places connected by a wire simply cannot be at the same voltage if there is any current flow along the wire. The V=I*R drops in the wire make this so. So both ends of a current carrying wire cannot be at ground. Can't happen. Ground is a SINGLE POINT in most cases, because there's nearly always current flow. A GROUND NETWORK includes one ground point and the rest of the network which is close to 0.000V.

To avoid mixing signals in the voltage drop down a wire, we separate current flows. So from the input jack, only signal should flow in the signal wire and ONLY SIGNAL GROUND CURRENT SHOULD FLOW IN THE SIGNAL GROUND WIRE. Running power supply current down the input signal ground wire therefore mixes all the electrical returns for the entire pedal with the input current. The only reason this is usually not a problem is that the effect is usually a small current user and usually is low enough gain to not have ugly things happen.

Usually.

So, my question....When I build a GGG ultra clean power supply, and it has + and - outputs....if I am not using this power supply in a typical fashion, where there will be output jacks....I just want to provide DC 9V+ hardwired to 1-2 circuit boards, (in a multifx board)...Do I just wire the - on the power supply to my enclosure, or star ground??

Look at the "ultra clean power supply". (As an aside, the name is misleading. It's no more or less clean than any other voltage-regulator-chip regulated power supply.). You see tha the + power comes from side-by-side pads. Likewise the - power comes from side-by-side pads. You can do anything you like elsewhere, but those connections are still there in the power supply. In your case do not wire the minus to the enclosure. Take one or more wires from the power supply board to the boards. Distributing power through the enclosure metal sounds good but is an invitation for problems.

If that is the case, can I do the following: For circuits that have like 2-3 ground points (like a boss pedal), Can I wire those grounds to the - side of the ultraclean power, and then also run a wire from the negative output on the UltraClean to the star ground? Thus making my wiring a little neater?

Frankly, you'll probably get away with it no matter what you do. However, the better way to do it is to run one wire from the power supply to each effect board and gather the ground points for that board on the board.

[sjaltenb]

Thank you very much for your help R.G.!

Very informative and helped very much. Thanks.