DC Adapter Question

[DocAmplify]

I've come to understand that some DC adapters are positive in the center and ground on the sleeve, and others are the opposite.  I've been looking at the icon on the adapters that indicate DC and most of them have the -ve on the left with a line to a circle, then a dot with a line to the positive.  In my mind, this is a graphical representation of -ve sleeve and +ve center, but I've never seen the icon with the + and - reversed. 

Does the icon really represent the polarity, or is it just a symbol for DC with no regard?

[artifus]

yes. dot centre, semi circle sleeve with polarity indicated.

[seedlings]

The symbol is the same, but the polarity is different on many power supplies.  As an example, most non-behringer guitar effect gear are center-negative polarity.  All other equipment (printers, notebook computers, cordless home phones, etc...) are center positive.  So, if you mostly pay attention to guitar gear, then that's mostly what you see.  Have a look at some other electronics around the house.  Careful when buying power supplies online too.

CHAD

[DocAmplify]

Thanks.  That helps.

Now I just have to decide which convention to follow with my build. 

[artifus]

centre negative will play well with most pedal boards. it's almost a convention.

[DocAmplify]

Potentially more difficult to isolate from the enclosure?  (which is contacting grounded elements of my circuit).

[R.G.]

Potentially more difficult to isolate from the enclosure?  (which is contacting grounded elements of my circuit).

It *requires* that your input jack not be one of the ones with a metal bushing, or that you put in insulating washers to keep it from contacting the enclosure. There is an exception to that, for the very specific case where the effect being powered is a positive-ground circuit.

[ashcat_lt]

What gets me is when you don't see that symbol.  Some will have a dotted line and a solid line - one above the other.  WTF is that supposed to mean,?

[kvandekrol]

What gets me is when you don't see that symbol.  Some will have a dotted line and a solid line - one above the other.  WTF is that supposed to mean,?

That's just the symbol for DC power...

(edit: just saw your post count and am realizing now that it was in jest!)

[DocAmplify]

Potentially more difficult to isolate from the enclosure?  (which is contacting grounded elements of my circuit).

It *requires* that your input jack not be one of the ones with a metal bushing, or that you put in insulating washers to keep it from contacting the enclosure. There is an exception to that, for the very specific case where the effect being powered is a positive-ground circuit.

I have a few projects in mind, and they're all negative ground. 

[ashcat_lt]

What gets me is when you don't see that symbol.  Some will have a dotted line and a solid line - one above the other.  WTF is that supposed to mean,?

That's just the symbol for DC power...

(edit: just saw your post count and am realizing now that it was in jest!)

I appreciate your confidence, but I was actually serious.  I could swear I've seen it both ways around, and always assumed it was meant to convey some info re: polarity.  Especially in circumstances where there's no other information.  I guess I've never really taken the time to look it up or even compare a number of such adapters...

If in doubt, it's best to test with your meter and make sure you know the polarity before you plug it in. Commercial pedals are built to fail under a reversed polarity situation.

[DavenPaget]

When in doubt , whip out the good ol' meter 

[DocAmplify]

When in doubt , whip out the good ol' meter 

That, I will do.  I was actually wondering because I'm about to put graphics on the pedal.  Since I'm likely to follow pedal convention of +ve sleeve I was wondering if I should mark it:

(-)----C-----(+)

instead of

(+)----C----(-)

[artifus]

http://wombatula.com/electronics/polarity.php#h1