Hi everybody ,my second posting here,I have to say ,midibox forum works GREAT 
I ve a question about ground:wich pin or way to plug the metal chassis to the core?and what else has to be grounded to the chasiss?please tell me all the ground connection I have to do except the knobs and faders of course.
thanks in advance
massi -italy (midibox 1.0 thorsten rule!)
Mainly only the chassis. Take any ground connection (e.g. just solder a wire under the core on some ground - the big stuff is always the ground).
Take care of isolating the power supply good from the chassis (could bring in some short). The other plugs don´t need to be grounded anyhow (MIDI conns, Banksticks and so on).
I think thats it… :)
Thanks again Pay_c
Ive solved the previous ainx problem,was a short
So just ground the core,no need for ainx or dinx..
best regards maximilian
Errr… just btw: (am a little ??? cause of your answer)
The ground, no matter if the GND of the core or of the AIN or whatever is everywhere the same! So it doesn´t matter wether you take the ground for the chassis from the AIN or the Core or whatever.
The only thing you shouldn´t do: Making ground “circles” - this means e.g.:
CoreGND—DIN1GND—DIN2GND—whateverGND—chassisGND—andbacktoCoreGND
This *can* bring in ground humming into all your signals if the circle is getting very long.
Greetz
Hi,
Analogue Devices Application Note AN-347:Shielding and Guarding is a great resource for “more technically” minded people. Giving detailed information about noise pickup and how to avoid it.
www.analog.com -> “Technical library” dropdown menu ->Application Notes.. and there it is somewhere 
Bye, Moebius
i have a relevent Q about grounding the core with mains grounding. because i am using an internal PSU (i know ;D, kool) and here in britan a we have a 3 pin mains plug (live, neutral, ground)
The Q is can the mains ground be connected with core groung ? will it not interfere?
you can read on if you like…
I had a wire form my radiator to ground myself while i was working with PIC (good point this), and i touched a serial port of my PC and i got an 80 volt shock. why? what? were? how? i was asking myself and belive me, it wasnt pleasent :(.
Strange things…
by the way i know it wasn’t 220v because i’m still here and it did feel more like 65 to 80v, belive me i’ve been shocked dosens of times so i’ve grounded my midibox so by brother woudnt have to expirience it too.
/edit: just spelling
The Q is can the mains ground be connected with core groung ? will it not interfere?
Yes, you should probably connect it. At least with all metal casing.
(With mains powered equipment with conductive parts to be touched by user, this provides protection agains hazardous faults (ie. short circuit from “live wire” to chassis) as it provides “return path” to ground, blowing the fuse)
Only thing to look out is creating ground loops - there should be only one path to the ground.
why? what? were? how?
I know the feeling. :o (Got it from an old coax ethernet cable and a radiator).
There’s a different potential between a “mains grounded” (?) computer case and the radiator.. so radiator really isn’t a ground point, more like voltage source Don’t ask me why .. 
Bye, Moebius
thanx for your reply.
i asked if i can connect the core GND to the mains GND because i was afraid that the core ungrounded might get some noize, i have grounded the mains strait away and its the choice between connecting the core and not connecting the core. will core get noize if its not conected to the metal case?
P.S.
why? what? were? how?
its more like : Ahhh! you mother f-f-f-f… !!!
Yes, just ground the core. As long as everything is connected to one common ground (point) external and internal interferences should be “sucked” to it. (Or, if this is MBSID, you can experiment: “With or without” - can you hear, what happens to SID noisefloor)
its more like : Ahhh! you mother f-f-f-f… !!!
Yup.. but it’s so much more pleasant to be able to curse than That 220v total blackout(CH!!)
Bye, Moebius
the case should be wire to the midibox ground by only one wire, taken from the Psu for example. Try to avoid ground loop.
For the radiator stuff, maybe you’re computer is not plug to earth, is it? if not, then you have the answer
I think it’s the same here, we’ve got neutral and phase on all plug, and earth on some.
As far as I remember neutral is the earth of the stuff that give you the current (nuclear plant), but as it comes from far away, it’s not the same voltage as the earth in your house. That’s why there is another earth on your plug putting the case to ground I think is for CEM stuff (is it the same word in english?), and then the best is to put it to earth.
take care that some IC that need heatsink has not always their metal parts wire to gnd… I remember when building a gain clone with LM3886 in non isolated package, which was internaly wire to -V (-35V!), and then a jack fall on it… makes beautiful smoke
Maybe I wrote wrong things here, and I would be pleased if someone can correct me, that’s the questions I always want to ask but always forgot…
For the radiator stuff, maybe you’re computer is not plug to earth, is it? if not, then you have the answer
Had to check this out. Extension cable has “ground”, but livingroom wall outlet doesn’t: Between extension cable “ground” and the radiator: Nice 110VAC, Ouch! (Of course I HAD to touch it)
take care that some IC that need heatsink has not always their metal parts wire to gnd…
..like 78xx vs. 79xx regulators. (Gotta remember that when building AOUT module..?!)
Pilo, Thanks..
Good tips and points out there,
Bye Moebius
Years ago I worked in an area with electronic equipment, computers, teletypes used as computer consoles (now you know how old I am) in an area wired by “licensed electricians”. I was touching one piece of equipment and leaned over and touched a teletype I was reading information from and got a dandy shock. Seems like the “electricians” had miswired ground in the shop and there was around 68 volts between grounds. Some equipment in that room ran on 120 volt, some 240 volt (both single phase) some on 208 volt three phase (all 60 cycle), some on 220 volt single phase 400 cycle, etc. Made my day go a bit slower till I found what was ok to touch and what was not!
Mickey
Mickey
I have a growing respect towards LIVING electricians
A friend told me that as he was with his father, who was doing service/ installation work at a big factory, how his father insured that cabling was powerless.. by just swinging a knife with insulated shaft, cutting through cable carrying 220v.. and same time checking which fuse that line was connected..
I did another check at my cabling. It’s still 110VAC between ground point of the extension cable and the radiator, even without anything connected, so it must be parasitic inductance.
Bye, Moebius
Hi all!
I have a question about grounding too!
Suppose the following setup:
A wall outlet with three terminals (including ground),
a (how do we say in english the T used on outlets to provide 2 or 3 outlets out of a single one, u get the point),
a pre-amp with a 3 terminal plug,
a power-amp with 3 terminal plug.
OK, we connect them alltogether, plug in our instrument and play.
The question is : Haven’t we made huge ground loops between the pre, the poweramp, the outlet and the audio signal cable’s ground??
Wouldn’t it be better to ground only the power amp and provide ground to the pre over the signal cable??
Thanks, uclaros!
You may be right, from an audio point of view. but from a safety point of view the way you currently have set up is correct. Guitar players have died from this ( so I’ve heard, though i believe a damp stage was also involved…), and you could geta nasty shock. though it could work just fine.
Well..
This is JUST a thing I am wondering about. If all the equipment are provided with grounding (or “grounding”, like in my case, but anyway same potential for “ground”) from power, and from audio connections.. forming a ground loop.
What to do? Nothing? Making “ground lifted cables” (no ground connected)? DI boxes (with transformer) boxes with a “ground lift” option?
Bye, Moebius
arumblack:
Really, only one path to the ground point is needed.. whatever it is. (Electrical potential between the players guitars ground point and the stage caused this.)
Bye, Moebius
yes it makes big ground loop, and sometimes you have too use DI box.
I think that ground loops can be a problem if they are near a tx or something like that.
I remember the first time I plug my gain clone (yes again :)) in a party (I never used it with 2 speaker before! lol) and the only sound we can hear was a big buuuzzzzz… because of ground loop (and this is when I knew what a ground loop was!! hehe)
the 79xx voltage regulator are not wire to gnd (the case)?? if 78xx are used like 79xx there is this problem, but I though that 79xx has got the case wire to gnd… have to check before putting the heatsink on my last psu then! lol
pilo,
and everybody else, we are learning from each other! And probably having some fun..
79xx have V input at the center pin, connected to case (metal).. (Only if I knew why?!)
Bye, Moebius
lol yes you’re right!!! I just checked (but I though I did it before)…
well, this time no smoke have to remember this when I’m going to put the heatsink
Thanks moebius!