There are two questions here. One is whether analog and digital grounds
can be connected together on a PC board connected to a MOTM-950. The
answer to that is, Yes, because the two are connected on the MOTM-950
itself anyway.
It's a different question whether a module can propagate noise through
the power supply connections into other modules. I am sure that is
possible. If noise could get through simply due to the analog and
digital grounds connected, then the MOTM-950 would be subject to this
problem for ∗any∗ set of modules supplied by it. Analog and digital
grounds have to connect somewhere. At one point is ideal. The 950
provides that point.
In the end whether you have a noise problem comes down to whether you
∗detect∗ a noise problem, i.e. you have audible noise or noise visible
on a 'scope. If you do, then it becomes a matter of tracing the source,
and, if you suspect coupling through power supplies, it is a simple
matter to disconnect the suspected modules to see if the noise goes
away. I haven't noticed noise from my Veeblefetzers (which have a bunch
of LED's), but if I detected a noise problem, I would disconnect them to
see if it fixed it.
I have my digital modules, including Veeblefetzers, the MOTM-650, CGS
digital circuits, Blacet Miniwaves, etc., on separate power supplies
from the VCO's, VCF's and VCA's in my synth. Right now I have a
MOTM-950 powering nothing but two Veeblefetzers, the MOTM-650, and two
MOTM-800 envelope generators. The other digital modules are on a MOTM-900.
-Richard Brewster
http://www.pugix.comMark wrote:
> On 10/26/06, Richard Brewster put forth:
>
>> It depends on whether your circuit keeps analog and digital grounds
>> separate. If it does, then there is no reason to connect these on the
>> board; they will be connected at the supply. If the two grounds do
>> connect at the board, it is not cause for concern. I am running a
>> couple of Veeblefetzer's off a MOTM-950, and the analog and digital
>> grounds do connect together on the board. I asked Paul S. if this would
>> be a problem and he said no.
>>
>
> I don't know what a Veeblefetzer does, or what sort of noise
> considerations there are in "Veeblefetzering". However, if noise is
> a concern, as it would be in an audio or precision voltage module,
> then, imho, it is best to keep the digital and analog grounds
> separate. If it were something like a logic module, then it wouldm't
> matter much.
>
>
>
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