Dimmers - noisy when off (CBus)

["Paul Robinson" <ukcueman@xxxxxxxxxxx>]

I expect/accept some dimmer noise when something is on partial power, but
I'm finding that
some of my 12v lighting transformers are producing a very high pitch tone
when they are
supposedly off. It's at the top end of the audible range and annoying when
you notice it.
These are running 12v halogen lights.

I've put a multimeter across this to see what I can see, and it shows that
there's a
voltage of about 46-50V on most of my channels when they are off, but only
two of these
are noisy. Is this normal? Is it a fault at the CBus end for there to be
any voltage at
all? Shouldn't off *really* be off?

The transformers are all the same type, so I guess I've just been unlucky
with the two
noisy ones. The two noisy transformers are attached to different CBus
dimmers (the 8
channel 1A DIN variety).

Any insights would be most welcome!

Thanks,
Paul