[sdiy] decoupling modules from power lines?

[Jim Patchell]

    I don't know how much power supply bypassing you have on your board, but,
Harry will tell you that I am a big fan of bypassing.  I try to put a 0.1uF cap to
ground on every single power supply pin.  The last board I did had 106 bypass caps
on it (Good time to by Kemet Stock ;^).  This will not garentee you won't have
cross talk, but, it at least eliminates the power supply for the most part.

    Also, the way the grounds are wired is probably more important than using an
LC filter.  If you are getting significant drops in your grounds, these will be
amplified by the opamps and other circuitry.  Good grounding practices are
important, and it takes a lot of practice and trial and error sometimes, to learn
how to do this.

        -Jim

Christian.Bergmiller at daimlerchrysler.com wrote:

> Hi,
>
> here is just another one joining the list...and the first message i'm sending
> is a question (what a shame) !
>
> I'm currently building a (small) modular synth with ASM-1 VCO's (added
> tri/sine), polyfusion VCF (OTA design),
> selfmade midi to vc (at89c2051) etc...
> Yesterday i discovered the VCO's had the tendency to lock (they even modulated
> each other - without any connection
> between them but the same power source) i fixed that by adding a tantal
> capacitor from the V- to ground on both VCO modules
> (from V+ to ground seems to have no effect so i left them out so far)
>
> Now i'm thinking about equipping every module with a coil followed by a
> capacitor to gound for the V+ and V- power lines.
> (tro prevent further problems so far undiscovered)
> I would try 1mH and 2,2uF, but would like to hear your suggestions bevor i
> order a greator amount of these values from
> my favorite supplier...
>
> Hope to hear something helpful :-)
>
> Christian
>
> (and please don't mind the bad english...)