Grounding with metal case??

[DeIVIoNaN]

 I am making a 7 loop looper pedal w/ bypass, i got this case online, that i'm not all that crazy about but its size is accommodating.. anyway......

i don't want a ground loop and it is a sheet metal case.... the ground runs threw all jacks? so should i leave all sleeve pins on the back of jacks unconnected?? is the only ground wire i need from dc plug to bypass switches ground lugs and then to only one jack?

https://www.flickr.com/photos/23193505@N06/14000405020/

ty in advance

[DeIVIoNaN]

or is this a stupid question? and should just wire as norm??

http://www.diystompboxes.com/smfforum/index.php?topic=87538.0

[Quackzed]

my thinking is, yeah you can use the case as a ground bus. and just pick one lug of one jack for ground connections. after all if you additionally ran a wired ground to all jacks, they are still all connected to the box, but now are also connected to each other via a wire so it is a ground loop. i dont forsee any additional problems with that way either really, in this particular scenario, but i don't think you need it wired... so long as the chassis has a good solid -uncorroded- -unoxidized- etc. connection from jacks to chassis . ground isn't always perfect GROUND- 0v but in this case ground is GROUND.

[GibsonGM]

With a metal enclosure, you COULD just rely on the case to provide a ground...but if that nut ever comes loose (WHEN it does), you lose your ground and it's VERY loud and obnoxious.    Ok, so we add a 2nd connection, via a wire...and now, we've assured a ground loop, which may or may not be an issue.  Sometimes, it's just fine.

It would probably work fine the way you have it drawn, in fact I know it would, but another neat way they avoid any kind of loops is to use PLASTIC JACKS (marshall style).  That's the reason they exist....then, the only ground connection you have is the one you actually solder to the jack.   It's good design practice to use them where you can.

I'd use the case as a bus for the LEDs but not the jacks unless you can be 100% on the connection to case.   Just my 2 cents.

[induction]

I agree with Mike that you shouldn't rely on the case for ground without an additional explicit ground wire. Dissimilar metals tend to develop a resistive corrosion layer between them that can break the electrical connection. However, I suggest that you not isolate the jacks from the enclosure. If you ground the enclosure you can take advantage of the electrical shielding it provides. I do this with all of my builds and I've never had a problem with ground loops in pedals. In this case, if the enclosure ground connection fails it's not nearly as catastrophic as it would be without the additional ground wire.

[ashcat_lt]

I'm not so much worried about any internal ground loop.  But what's going to be attached to all those jacks?  That's where you're you most likely to create ground loops that make a noticeable difference, and where you might want to look at isolating those jacks and maybe adding ground lift switches.

[wavley]

I'm not so much worried about any internal ground loop.  But what's going to be attached to all those jacks?  That's where you're you most likely to create ground loops that make a noticeable difference, and where you might want to look at isolating those jacks and maybe adding ground lift switches.

Yeah, I'm gonna second that.  I think that I've created just about every ground loop you can have.

[induction]

That's a good point. I hadn't considered the difference between a looper and a regular pedal. I use daisy chains for power all the time and haven't had a problem, but it's definitely more of a possibility. You could still ground the enclosure for shielding, though.

The ground lift seems to be the important part. Without that, I don't see how the isolated jacks would help.

[GibsonGM]

Well, the isolated jacks allow you to have your gnd wire go to the jack...and ONLY that wire grounds it. The jack won't ever create a gnd loop this way, even if it should touch the enclosure as the barrel is insulated.   This is just good design practice, but usually found in high-gain circuits, amps, etc.  Things doing a lot of amplifying.  In a looper's case, yes, the lift might come into play and deserves a lot of thought!

It's irrelevant whether the case is grounded by the jack or by a dedicated wire elsewhere, but I do agree you SHOULD ground the enclosure to create a nice beefy shield!  I didn't mean the encl. wouldn't be grounded, just that jacks should be separate from the encl. or else by definition they ARE a ground loop.   If not touching, they're not making a loop.

FWIW, in every pedal I've built I use metal jacks, that have both a gnd wire and also touch the enclosure, LOL.   I've never had a problem this way....I always use the gnd wire on a jack since they WILL work loose over time and make terrible noise.     I'm just relaying *good design procedures*.    Someday they might save your bacon or something, ha ha!      On amps, I always use plastic jacks and keep them isolated....