You're Grounded! AIN r3 : Question and Suggestion.

[dengel]

I've got all my boards built, and my LCD is displaying good stuff (random midi events, at this point. I'm interested in small-scale testing the pots and faders I bought with the two AIN boards I've built. Obviously, unused inputs need to be clamped to ground, but good info on just what this means is hard to find.

I assume that this is a "floating ground", and that any large hunk of metal will do? Where do you guys ground your unused inputs? I've read that the ground is the outlying areas on the core PCB - do you just solder your ground wire there and connect the multitudes of other inputsto that ground wire?

In a future rev of the boards (Smash!) might it be possible to offer a pc-type jumper that would effectively turn off (or on, whichever is easier)  or send to ground all but one input on each board for testing purposes, or at least turn off all but one of the AIN's (say, just J1 is a part of the circuit?)? Grounding 31 pins just to test an AIN board seems like somewhere that some improvement could be made to the system

In any case, my issue is the question of grounding these unused inputs. Is there an easier way to do it than connecting 31 wires and soldering them to ground? For instance, could I just ground AIN's J5 a1,a2, and a3 to vss and then I don't have to worry about those inputs on J2-4? I have put all the 4051's in the sockets, btw if that matters.

Once I find this out and make a test plan, I'll write up a Wiki article so this question doen't have to be asked again!

Don.

[smashtv]

In a future rev of the boards (Smash!) might it be possible to offer a pc-type jumper that would effectively turn off (or on, whichever is easier)  or send to ground all but one input on each board for testing purposes, or at least turn off all but one of the AIN's (say, just J1 is a part of the circuit?)? Grounding 31 pins just to test an AIN board seems like somewhere that some improvement could be made to the system

It's already there....

Notice the red jumpers on the core on the photo in my LCD page (J5a+J5b)....

http://www.avishowtech.com/mbhp/20x2.html

Don't jumper all connections though, as this will short 5v to ground, and let the magic smoke out of your power supply.  ;)

On the grounding question, your pot ground(s) need to tie to any of the many ground points I added to the AIN board.  The best (read: lowest jitter) way is to run one ground wire from pot to pot for all pots, then tie that wire to ground.....This will eliminate ground loops that raise the noise floor of the circuit.

Best

Smash

[dengel]

Ah, Thanks! I never saw that photo... I'll add it to my "how to ground" document that I'll write about this. Thanks! Time to scrounge up some jumpers from old motherboards, etc.

[dengel]

On the grounding question, your pot ground(s) need to tie to any of the many ground points I added to the AIN board.

Tim, do you mean ground points on the Core board? I don't see anything on the AIN for grounding, except maybe the four lil' through holes coming of Ic2-4... not sure what those do.

[smashtv]

J7-J10, Vs=ground, Vd=5vdc.

The unmarked through holes are vias that pass ground from one side of the board to the other.

Again it's best to wire all pots +5 together, and all grounds together, then run one ground and one +5 back to J7.  J8-J10 are only for convenience on non-standard builds....(for per-group isolation, which will add jitter if used on a standard build)

Be sure to take a look at http://www.ucapps.de/mbhp/mbhp_ainx4_64pots.pdf, it shows everything ya need to know.  ;)

Best

Smash