1176 seems to work ... Pics

[ChuckD]

Thanks TubeJay!

I put the grounds together as you described but it is not the problem.
I've isolated the problem to a ground loop between the two boards, I know this because if I unplug one then the remaining goes quiet.

So If I unplug just the PIN 1 of one of the channels (both input and output) I get quite operation. Now is this ok to do this? Is the signal with no PIN 1 still balanced? Can someone explain this?

What are some other solutions? I dont have another transformer and really would like to use only one.

-ChuckD

 

[gyraf]

ALWAYS connect to one, and only one, ground/0V.

Make this the ground pin at one of the input XLR's.

Also connect PSU 0V through this point. And chassis ground.

 

[tubejay]

Gyraf, I'm a little confused about the grounding thing. Why are there 2 points to connect the PCB to ground, if we're only using one? I guess there are two possibilities, which is best?

1. Earth ground on AC plug to chassis to XLR out ground to XLR in ground to PCB ground plane.

or

2. connect the grounds on both XLRs. Connect both to 0 ground on their respective PCB I/O connections. Connect one of the XLR's ground to the chassis ground. Connect the earth ground from the ac cable to chassis.

I don't understand why there are two points to connect to ground on the PCB, if we're only using one??

Should I change mine, even if it's dead quiet??

Thanks,

Jay

 

[radiance]

@Tubejay: As far as I know #2 is the way to go.
In this case we use both "ground to pcb" points.
One is used for shielding the wire between the XLR and the PCB and is also connected to the chassis ground. The other one is only for shielding the wire between the XLR and the PCB.

 

[matthias]

tubejay, did you cut the ground plane on both pcbs, like it is mentioned in the 1176 help thread ??

 

[tubejay]

Yes, I did, and I have no hum at all. I should have listened to it before I cut the ground plane to see if it was there. However, I just cut it how everyone else did.