stupid question I know

[takamineman]

Do you always ground the circuit to the ground on the input/output jacks (or speakers)?  Then everywhere else the schematic shows a ground comes to the same wire?
Thanks for any help from a rookie!
Greg

[GibsonGM]

It's not a stupid question.   Stupid would be trying to build things without asking the questions you need to get the info you need to make things work    The question shows you're aware that something needs to be considered before jumping in and 'grounding' all over the place!

Basically, yes - you have the right concept.

I use 'star grounding' (something to look up).   I make a point on my PCB, usually a 'buss'...a wire underneath it that will go to "-" on my negative ground circuits (as most of them are, 99% of the time.  A very small few things are POSITIVE ground, some old fuzzes and stuff - not common, but use + as the ground.  Another topic entirely but same in concept!).   All of my schematic ground connections go to this buss.       

The buss is then connected to the jacks and "-" of the battery, with the TIP of the jack being for signal connections.  There is some switching along the way, to turn the effect on when you plug into the input jack.    Here's one place to look around to see (stick to true bypass setups for now):  http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=33&Itemid=27


As you go along, you'll get better at learning which parts of a circuit are 'sensitive' and have to go straight to ground with no 'detours', and which are less critical and could take a bit of a 'meandering route', if you will.    Read up on star grounding (and WHY it's important, with respect to gain stages etc).   Generally, you want a very direct and "clean" ground path early in the signal path to avoid creating currents on the ground buss which make noise.  But that comes with time, and is more of a layout issue.

Happy reading, and good building! 

[Mark Hammer]

For every person who thinks they are asking "a stupid question" there are usually at least 10 who don't have the courage to ask it but really need it answered.  So, it's never a stuid question; it's a public service.

[takamineman]

Thanks for the help fellas!

[bluebunny]

. . . (or speakers)?

Just be careful with speaker connections: some designs don't ground either side, for example, the Tiny Giant.  The schematics should show clearly whether you should or not.

Please keep asking "stupid questions".  It's the stupid answers you have to watch out for!      (But thankfully, not too many of those around here!)

[pinkjimiphoton]

try and make all your grounds connect to one wire or spot, then connect that to the ground lug of your input jack. it's called star grounding, and works great. if you use a metal box and know you have continuity between input and output jacks, you don't need to connect the ground on the output side.

like, say you have two pots, each with one lug tied to ground. tie those together. tie that to the board ground. then tie the board ground to the input jack sleeve connection only. no ground loops that way.
the idea is to have a whole bunch of branches all coming back to a single trunk, like on a tree. but don't overcomplicate it. if your board has several potential ground points, only use one.

sometimes it helps if you're getting noise or hums to "float" the ground with a small resistor... other times it won't work at all like that.

most people connect the ground on the input side, but some circuits seem to work better on the OUTPUT jack in practice.


i concur, there is no such thing as a stupid question. you will learn more here faster asking a lot of questions than you will making assumptions and guesses, and every time you ask on the forum, you and someone else will benefit from the knowledge shared here, so...

first, try the search function at the top of the page... and if you don't find info (unlikely) or so much it makes your mind hurt (more likely) then ask whatever ya need... and almost always someone here will try and help.

[GibsonGM]

I don't let any jacks float, hoping contact with the chassis will be enough.  If (when) they come loose, you get a GAWDAFUL noize until you figure out what happened.   I've done that in practice (not live, thankfully!) and will never let them float again.  I either tie the output jack back to the PCB ground or to the input jack ground.

I know it's counter-intuitive to the star grounding scheme, but at the low voltages/currents that we normally see in stompboxes, a ground loop is not at all likely to occur if you ground both jacks.  This is what I was told when I too was a newbie     Otherwise, I agree that the rest of the star ground method is the way to go!

[pinkjimiphoton]

works for me. i also find in some high gain situations, you need to ground the back of the pot casings too.
gus smalley's OUSB comes to mind. i couldn't get it to work until i did that.

[tubegeek]

There's another thread going now with a similar question about all the "Vcc" points connecting on another schematic.

Just to - I hope - add clarity here, the ground symbol or other labeled nodes on a schematic are there to avoid a mess of redundant wire lines on a schematic, with the intention of making it clearer to read and easier to follow the audio signal flow through the circuit. So if there are any points that get many connections, like the positive and negative DC power supply connections for a typical example, the person drawing the schematic will just label them each with their proper label instead of showing a wire back to that point.

Another similar practice is to label sends to, and returns from, a subcircuit that is easier to draw all by itself on a different part of the schematic. Sometimes a reverb or a tremolo in a guitar amp will be drawn this way, for example.

[GibsonGM]

Good point, Geek...a place to see the difference is on many older tube schematics, where you see an actual ground bus running along the bottom.  After that, they made it simpler by just 'tagging', like Geek just said.    When I started, that made a bunch of new questions for me )   Eventually it will all come together.