[sdiy] Matrix 1000 grounding question

[Tom May]

harry <harrybissell at prodigy.net> writes:

> Hi Tom:
> 
> My Matrix 1000 is noted for acoustic hum. The cheap-o power transformer
> magnetic field that escapes rattles the top and bottom lid.

Yes indeed.

> If that is possible... it might be that the magnetic field is causing
> circulating currents
> in YOUR chassis as well... and that for that reason the earth ground and
> signal
> geouns are not the same point as the designers intended...
> 
> Whatever wiring works for you, I'd do that.

Ok, that makes me feel better :-) The final solution involved moving
the grounds of the pi filter caps from earth ground to signal ground,
and in addition there is a trace on the PCB that surrounds the pi
filter components which is at earth ground, and to eliminate all the
electrical hum this trace had to be connected to signal ground and
insulated from the screw holding the PCB to the case.

> I'm convinced that all (other) engineers are either INCREDIBLY stupid... or
> geniuses so far beyond my ken I can't even dream of what they
> accomplished...

If other fields of engineering are similar to what I'm familiar with
in software, I'd say "incredibly stupid" wins most of the time.
"Incredibly lazy" is right up there as well.

Tom.