How to connect to the chassis to the ground? does it need to?

[tenser75]

In my PCB design I'm using neutrik jacks, plastic, and I realized that nothing really touches the enclosure
with old school jacks they were touching, but now i don't know how to make the connection.
I could solder wire from the PCB ground to the back face of the potentiometer which is usually metal and is touching the holes...

is there any other method out there? maybe some wire that connect to the back plate/screws of the enclosure?

I'm looking for a pro solutions as it is meant to be manufactured in medium scale, so it can't be a temporary solution...


Second part of the question: does it actually need the PCB ground to be connected at all to the enclosure? to me it doesn't sound bad or anything...

[Rob Strand]

It's generally a good idea to connect ground to the case.   

I generally connect the ground of the connector which has the longest external cable connecting to it to ground. (excluding other details.)  If you have a nice ground lug somewhere it's obviously that but if you had that I suspect you wouldn't be asking.  One method is to solder a wire to the back of a pot, it's a bit brutal but that's how it's done in a guitar - assuming your pots are metal, solderable and metal case has a conductive path to the thread.   You can also get large ring lugs that fit onto one of the connectors or pots - I'd probably go with the input socket here.

A lot of modern stuff have springs that poke out from the PCB and connect to the case.   When you do that you have to be careful of what metals you use.    I believe Behringer effects use this method to connect the PCB ground to the metal back-plate. 

[Edit: I've also put small solderable ring lugs under panel screws or PCB mounting screws]

[tenser75]

i just found that NEutrik also sell this model to ground to the chassis!!!

http://www.neutrik.com/en/audio/plugs-and-jacks/slim-jacks/nrj6hm-1

it will be good for small batch production

[Rob Strand]

Even better. I thought you might have 50 isolated ones already.

[bool]

If you are a "serious builder", you could in theory consider your current situation as being a very convenient one to add a "ground loop break" circuit (usually a resistor, 2x antiparallel diodes and a cap).

[GibsonGM]

Second part of the question: does it actually need the PCB ground to be connected at all to the enclosure? to me it doesn't sound bad or anything...

I know we're talking low voltage here, but it doesn't hurt to be thorough....If you're dealing with line voltage, you MUST have a dedicated chassis ground near where the power cord enters the chassis (usually EIC connector that makes permanent and reliable mechanical contact with the chassis (read: bolt and star washer), and stands alone, no other wires connected to it.

Then, typically, your pcb or point to point, what have you, will be of the 'star grounding' variety, and have one point of contact to the chassis of its own, which is the real "pro" design, but may be inconvenient on a small stomp, so jacks are frequently used.   This portion can (and probably should) be followed for stomp box layout.   Star grounding is a great topic to do a little reading up on to avoid contaminating your nice signal with the junk on the sewer line.

[Phoenix]

If you are a "serious builder", you could in theory consider your current situation as being a very convenient one to add a "ground loop break" circuit (usually a resistor, 2x antiparallel diodes and a cap).

The chassis in a class 2 appliance (like a typical effects pedal, and anything powered by an external isolated power supply - which is every pedal power supply on the market that I know of) is not the appropriate place for a ground lift circuit, it will only increase impedance between the chassis and circuit ground, and so increase noise. It will not remove ground loops in effects pedals that only receive a safety earth reference from other equipment they are connected to (like the amp at the end of the chain).
If however you are building a mains powered (class 1) pedal that is referenced to safety earth, then a ground lift circuit may be appropriate to avoid ground loops. Even then though, safety earth MUST remain connected to the chassis with its own dedicated bolt with toothed lock washers and Nyloc or double nuts and Loctite, the ground lift then goes only between the chassis and circuit ground.

Second part of the question: does it actually need the PCB ground to be connected at all to the enclosure? to me it doesn't sound bad or anything...

Yes, you must connect the chassis to signal ground - otherwise the chassis itself acts as an antenna, picks up more electromagnetic noise from the environment, and couples it more directly into your circuit. By grounding a conductive chassis it acts as a Faraday cage and couples any noise from the environment to ground where it won't contaminate your signal. Having a floating conductive chassis is actually worse for noise performance than having no shielding at all, as in, you'd be better off using a plastic case than a metal one and not grounding it.

[tenser75]

Thank you guys!

[tenser75]

Even better. I thought you might have 50 isolated ones already.

Yes i'm using the the plastic Neutrik M series and the PCB is designed to accept those ones...

I just noticed these Slim models have actually different dimensions, so I'm not sure I want to redesign and prototype again the pcb... argh

[Phoenix]

If you're using pcb mount pots that have mounting pins which are not circuit elements, they usually make continuity with the bushing (check this with a multimeter though, don't assume!). I make custom schematic components and footprints in my EDA, and connect this "fourth" terminal to ground. With multiple pots it also allows a little more redundancy in the chassis ground.

[tenser75]

I noticed inside a Malekko pedal they are using this small component...very smart
can you help identify this component? where can I buy it?

those two lips are "springy" so they touch softly the chassis

[Jdansti]

In addition to what others have offered, there are washers with a solder lug on them. Just slip the washer over the threaded end of a jack or switch and run a wire from the ground on your board, DC jack or negative battery terminal to the lug.