How to ground "properly"?

[Fancy Lime]

Hi there,

I usually run my ground connections in the housing to a single point on one of the jack sleeves (in or out) star style. The idea being that with star or tree grounding, there are no ground loops that can cause noise. However, I rarely use isolated jacks. The enclosure therefore does create a loop. On the one hand, this seems to be the way most people do it and it does not seem to create obvious problems for most people. I never had ground loop noise trouble. On the other hand, now that I think about it, it seems like poor form.

What do the professional EEs say? Should we be using orthodox star ground and use isolated jacks? Or should I stop worrying and love the fuzz?

Thanks and cheers,
Andy

[EBK]

Short answer: stop worrying.

Medium answer: proper grounding is part religion, part science.

Long answer:  (perhaps I'll write this one later).

[Fancy Lime]

Short answer: stop worrying.

Medium answer: proper grounding is part religion, part science.

Long answer:  (perhaps I'll write this one later).

Part religion, part science, huh? I'm not normally one for the New Age stuff but if it comes with extra holidays and celebratory cookies, sign me up! I am planning a Maximum Mojo treble booster build, which is what got me thinking about grounding in that amount of detail in the first place. Exactly the right place for religion and science I think I will be going with point to point and was considering making the ground point an oversized screw in the middle of everything. A copper screw if I can find one the right size. If not, I have access to a sputter coater, so I may take a stainless steel screw and coat it with gold. Yes, that is deliberately insane. I prefer the look of copper though and we only have gold and platinum for coating, so we'll see.

Andy

[anotherjim]

I'm not an EE so shouldn't answer.
Merlin may be an EE, he wrote this...
http://www.valvewizard.co.uk/Grounding.pdf

[EBK]

To explain the religion aspect, consider this:
You create a star ground to avoid/reduce ground-related noise, right?  However, you admit that you cheat a little, which causes you to feel guilty.  You have observed through science (we'll leave the question of rigor out of this) that your ground loop transgression has no objective negative consequence, yet you look to the actions of others in society to see if what you are doing is wise.  Despite seeing that others have grounded circuits in the same way, you still feel guilty, so now you are seeking absolution of your sin or an authority figure to show you the right path.  If someone shows you a grounding technique and declares it to be "right", you might be prepared to give that declaration weight in future projects, despite it not affecting your earlier objective observations that there is no perceivable difference.  Thus, you would be prepared to apply principles of faith in grounding your circuits.   

Heavy stuff, right?   

For what it is worth, I have a M.S. in E.E. (but no real professional experience as an engineer specifically).  I defer to the wisdom and expertise of others.  Anyone who says that I am wrong is also right. 

[EBK]

And, here is my "sermon":
Your enclosure should be used as a shield, not a ground current conductor.  Grounding the enclosure at only one spot ensures this.  Note that this means you would not connect both jack sleeves to the enclosure.  I isolate one jack with fiber shoulder washers. 
Never ever ground just one jack sleeve and rely on the enclosure to ground the other jack.  I played a gig where the input jack of my tuner pedal got loose and intermittently lost its ground.  Loud popping during tuning is not appreciated by an audience.

[antonis]

The enclosure therefore does create a loop.

Of resistance, maybe, in the region of femtohms..
(well, not so low but practically non measurable even with the most accurate DMM..)
Also taking into account the light stombox currents, I'd encourage you to follow EBK's short answer..

[EBK]

[ ]
Edit: I've started rambling again.   

[Fancy Lime]

@Jim
Thanks, nice resource, which I did not have on the radar. Never built a tube amp. Yet...

@Eric
To expand on the religion aspect: There is one thing I regularly need to explain to students, namely how do we know which information we can trust. There is, imo, a difference between asking an engineer and a guru. That difference being that the engineer will be able to back up their assertions and I can evaluate if I want to trust them, whereas the guru says "because I said so!".
You are right that I seek wisdom despite my own experience. But the reason is not that I long for an authority (in fact "authorities" of any sort can f... right off as far as I'm concerned) but that I realize that my own experience is limited. I try to expand my data set by including trustworthy sources to then draw my own conclusions rather than take the wisdom handed down to me for granted. My home environment is not as noisy (magnetically and electrically) as a stage may be, so I need outside data sources.
That being said, I still appreciate your sermon. It contains the data I sought (albeit in digested and interpreted form) to now evaluate when it is or isn't appropriate to take extra precautions. The tuner anecdote is useful info of that sort as well
Whisper at a party: What I'm planning is a first-in-chain booster, which will most likely be followed by some very high gain distortion. So if that whisper is ever relevant, it is here. More like breathing into a microphone with the PA set too loud. Still not relevant when the band is playing but potentially annoying in between.

@Antonis
My worries do not stem from resistance but from inductive coupling into loops (see section 15.2 in Merlin's writings that Jim linked).

Thanks and cheers,
Andy

[stallik]

Wherever you end up connecting the ground, do it with a really wide braided cable and big bolt just to match the enormous components

[Marcos - Munky]

What I learned from experience:

Some circuits are sensible enough to need a proper grounding. Most of them aren't used for guitar. But some of them are indeed used for guitar.

Which ones? Well, tube amps, mid+ gain tube preamps and very high gain solid state circuits. Basically, for almost all circuits you have to plan wiring (size of wires and where exactly they have to be, to avoid noise), you'll probably have to think on grounding. The best way (according to lots of people) is the star grounding.

If you're building something that the wiring doesn't really matter, then don't worry at all with grounding.

[Fancy Lime]

Wherever you end up connecting the ground, do it with a really wide braided cable and big bolt just to match the enormous components

The fattest house mains solid copper cables that my local hardware store has, war what I was thinking. But I have some flat braided grounding bands somewhere. Will check!

Andy

[antonis]

My worries do not stem from resistance but from inductive coupling into loops (see section 15.2 in Merlin's writings that Jim linked).

Merlin clearly states :
> the ground loop current will generate a noise voltage across the resistance of the shield <

Both underlined quantities are negligible on stompboxes..

[vigilante397]

I agree 100% with Erik's first answer, as I'm in the "don't worry" camp. I build everything from FV-1 digital boxes to high-gain tube preamps, and I've never had issues from ground loops. I let both jack sleeves hit the enclosure and wire them both together and into the PCB. I use ground pours on my PCBs, but not solid ground planes. There are absolutely circuits out there that require meticulous grounding, but I apparently haven't built any of them yet.

[slashandburn]

I'm lazy and lack foresight. Typically I'll leave my ground wires until last when boxing up, then I'll just grab them all and twist them together, add a big blob of solder and cover with a bit of heatshrink. Then I'll tuck the resulting mess away somewhere out of sight, out of mind.

I used to always use one plastic jack and one metal one, worried about the ground loop "issue" but somewhere along the line I stopped caring and never had much of an issue.

All that said, I don't sell anything and only do this as a hobby so I really don't care about the guts being neat and tidy. All care about is that it works and whether I like it more than my other fuzz or tubescreamers. Grounding only enters my mind when I'm troubleshooting something that doesn't work.

[soggybag]

I ground to the sleeve on the input jack. I usually run a wire from here to the sleeve on the output jack. This makes the enclosure a possible ground loop. Sometimes I'll skip the connection which grounds the sleeve on the output jack through the enclosure. This has the problem of popping if the output jack is loose. It's sort of a compromise, adding an insulator to the jack requires extra parts.

[ElectricDruid]

I'm with the "If it ain't broke, don't fix it" school of engineering. Thus I wire both jack sleeves to ground and let the enclosure also parallel that connection. In theory there might be a tiny risk of a problem. But it's never happened, so I've never had to fix it, and I think Antonis provided a reasonable justification for why that's the case.
In my view, on the other side is the improved reliability of the ground-to-case connection (which *is* important since it provides shielding) since you've got two jacks doing the job instead of one. That means if one works loose, your guts are still shielded. YMMV

[bluebunny]

I'm a fan and adherent of Eric's short answer, which has much merit.

If you really want the science and real-world advice, head over to Muff Wiggler and check out any of Graham Hinton's posts (he's an ex-SSL designer and really knows his stuff: argue with Graham at your peril!).  He pulls no punches in educating people about grounding, earthing and screening (and how they are all different).

[Fancy Lime]

Hey guys,

appreciate all the helpful comments. The only problem is, you are all being reasonable! I want to build something unreasonable! Kidding aside, your points are well taken. If I never had a problem with the enclosure ground loop, and y'all never had one either, we can probably assume that our combined experience covers a pretty large range of real live (see what I did there?) conditions. If making it 100% ground loop free is only good for mojo points, my mojo build is going to have isolated jacks and no loops whatsoever. I need as many buzzwords on the feature list as I can have Plus, I like the feeling of amp-style jacks anyway.

[ ]
Edit: I've started rambling again.   

Don't stop rambling! This is the kind of thread for that 

My worries do not stem from resistance but from inductive coupling into loops (see section 15.2 in Merlin's writings that Jim linked).

Merlin clearly states :
> the ground loop current will generate a noise voltage across the resistance of the shield <

Both underlined quantities are negligible on stompboxes..

You are right, if the ground resistance is negligible, then the effect is negligible. I had to think about that some more.

Andy

[antonis]

Merlin clearly states :
> the ground loop current will generate a noise voltage across the resistance of the shield <

Both underlined quantities are negligible on stompboxes..

You are right, if the ground resistance is negligible, then the effect is negligible. I had to think about that some more.

Electrical resistivity for copper is 1.724 x 10^-8 Ω m (0.0174 μΩ m) and electrical resistivity for aluminum is 2.65 x 10^-8 Ω m (0.0265 μΩ m), so you'll able to compare resistances of "some" length of AWG23 wire and total enclosure resistance..

just for info:
https://www.engineeringtoolbox.com/copper-aluminum-conductor-resistance-d_1877.html
https://hypertextbook.com/facts/2004/ValPolyakov.shtml

I presume you're able to calculate solid materials "volume" (i.e. cross sectional area X length for wires and total surface area X surface thickness for enclosures..)
In case you're too lazy to implement geometry formulas, take my word for aluminum enclosure internal ground wiring resistance is MUCH higher than enclosure itself..