Need clarification on grounding / shielding!

[Lysergium]

How to ground/shield a pedal? I'm a bit confused on this:

If you mount your input and output jacks, to the metal case of the pedal, and leave the ground lug blank, and only wire the input and output lugs, this would mean that theoretically, the case connects the shieldings of the output and input wires, so the whole pedal circuit is basically "inside" of the cable's shielding, just like the signal wire is inside of the shielding.

But then, if you do wire the ground lugs of the jack to the ground of your power source, which is what i see done on guitar pedal building videos, then you are connecting the signal ground of your guitar/amplifier to the ground of the power supply of the pedal. A guitar signal is AC and very low, the power supply is DC and quite high compared to the signal voltage, so I have trouble imagining, how this doesn't cause severe issues. Doesn't this mean that the DC current can now travel through your instrument or to your amp, through the shielding wire, and cause damage to the pickups or something like that?

Can someone please provide some clarification on this issue?

[GibsonGM]

At least one ground connection must be made to your pedal enclosure.  Most would not trust only 1 wire with this, either...I have always done both ground lugs of the in/out jacks, and NEVER have had an issue with noise. We simply are not dealing w/enough power flowing in these boxes for it to be a problem in anything other than rare cases...and it seems that ALWAYS, the jack that counts only on the enclosure to make contact will come loose, leading to a HUGE horrible noise on stage during your set.   

All grounds do eventually connect together, yes, generally speaking.    It depends on 'how far along in the chain' you are, whether there is noise generated as a result of this.   Our pedals are on the 'quiet end' of the chain, so no worries    Those big noise currents are sent to ground right away...

HTH, welcome to the forum!   

This might help a little, and explain it better than I can:

http://www.valvewizard.co.uk/Grounding.html

[antonis]

What Sir Mike said..


Shouldn't post something like this in the presence of a pro painter..