PLAN B analog blog

the best solution is powering the M15 if you can from an entirely
different rack.  If it's the only one you have, then follow the center
most connection suggestion made previously.

There's something that all of the current manufacturers of Eurorack
Racks (actually, not sure about Cwejman) have in common:  absolutely
no power management.  The manner in which they dasychain the power is
about the worst possible way it could be done, for all the reasons
you're experiencing.  Modules which by nature (most LFOs, not just
Livewire) and anything with a microp in it tend to make noise which is
transferred through the ground line.  If there are audio modules
powered on the same row, or at worst case from the same supply, all
the noise (usually associated wth zero transitions, when something
crosses or hits zero volts) picks up that noise.  What is required are
separate lines directly from ground to all of the connectors on the
row of the bussboard.  A failsafe solution wold be to power contrl
modules and audio modules from separate supplies.  This wold fix the
proble entirely.

If you scan through the letters on this blog you'll notice this is
exactly what we're planning with the Plan B case. There will be one
bussbiard to each row, but all grounds will be going directly to the
power supply return and every other connector will be physically 
offset form one another, one labeled AUDIO and the other CONTROL.  We
may actually power each of these from a different set of regulators.

~m