can these be used to attach metal box to circuit ground?

[Andy]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2559626862

check out this auction.  Can these be used to connect the ground of the circuit to the metal boxes?  I know the metal part of the input and output jacks are connected to the box in the same manner but would this cause a hum or any other side-effects?

[Rodgre]

You should be able to connect circuit ground to the enclosure this way. i would still connect a jack to circuit ground as well, without causing a ground loop, but there's no reason that I know of that it shouldn't work.

Roger

[Mike Burgundy]

any conducting metal part that connects to both ground and the casing will ground the casing.
If you hook up more than one ground point, you risk ground-loop hum.
The best point for case-grounding is the point that's most vulnerable to interference - which in most, if not all cases is the input jack. I used to use Carling connectors (isolating the output jack ground from the case, or not running a ground wire to it), although I'm now testing some plastic/metal hybrids that have an extra "outer threads" connection, aside from the ground (sleeve) contact.
These things are brilliant for mounting PCB's though - I use them all the time. I don't want these to contact any part of the circuit though.
Drill the pcb, mount these standoffs and their bolts on the PCB, and use epoxy glue to put the assembly where you want is. When the glue has dried, unscrew the bolts and assemble the board. Works great.

[Andy]

cool.  So now I have another question.  to connect the grounds of the input and output jacks, do I NOT need to use the box as the connector?  or should I run a wire from one to the other?

Another question is...what is a ground loop?

[Mike Burgundy]

a ground loop is well, a loop that's all connected to ground.
Think of it this way: you hook up both in- and outputs to ground. You also allow them to connect to the case.
The ground lug of both jacks are connected to each other via two routes: the ground/circuit ground, and the case. You could go through circuit ground and back through the case, circling round forever. This is a ground loop.
In most cases, this is not a problem, especially on this scale, but ground loops are sensitive to electromagnetic interference - they start working as antenna coils.
They can be really nasty when the loop is a great big one - for instance when you use two amps that are grounded through wall-ground (thus connected to each other via the wall socket) and also connected through the signal ground - this can hum like crazy.
In effects pedals, it's not very critical, but it doesn't hurt to work neatly and take precautions anyway.

Using the box as a conductor works just fine.
Since it is good practice not to run more than one connection (creating a loop) just the case connection is enough. If you want to be really really picky, you can isolate the output jack from the case (plastic washers), and run a wire from circuit ground to both in-and output jack. The case is grounded by the input jack. actually, stargrounding the entire circuit including the output from the input ground would be perfect.
Rest assured, you don't need this for the majority of effects. Use common sense, and rethink your grounding scheme if anything gets noisy.

[Andy]

excellent.  I will use the case as a connection point for my two jacks and will run a wire from the stereo input ground lug to the circuit ground connection.  I will NOT connect the circuit ground to the box via stand off's.  I will simply glue them on.

Thanks a lot guys!!!!  Are those standoffs a good deal?  Price-wise?

[Ansil]

i usually connect the input jack the side that connects to ground. to the board as my ground point. since the metal jack connects to the metal box.  also i don't even connect the output jack to ground.  as long as it is tight it will ground through the metal box...  no problems with it so far.  i picked up that from blues pearl.

[Andy]

What's Blues Pearl?

[Ansil]

this guy named robert made these great pedals.  you would swear they had tubes in them.  but they didn't.. i have one of the schematics for his pedal. it is a cross between a marshall guvnor a tube screamer and a boss od pedal.