Doepfer

--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:
>
> > Hello
> >
> > First time on this forum.
> >
> > I've just bought a Doepfer modular and I'm have a slight problem
> > with the A101-1 Vactrol filter.
> >
> > Whenever I connect anything to one of the CV inputs I get a lot
> > of background noise/interference.  This happens even when the
> > corresponding CV control is zero and even when connecting to
> > sources with no control voltage output (e.g. mixer input or reset
> > on LFO)- so its not CV opening the filter.
> >
> > Any ideas anyone?
> >
> > Cheers
> >
> > Carter
> 
> That's a very unusual behaviour because zero CV should be the same as an
> open CV connection. I'd recommend to return the module for repair. I have
> never heard of such a behaviour (i.e. connecting zero Volt CV that affects
> the sound) and have no idea what could be the reason (maybe it a problem
> with a GND loop ?).
> 
> Best wishes
> Dieter Doepfer
>



Thanks for the help Dieter.

I have noticed that the problem only happens when connecting the A101-1 to the modules on the MIDDLE row of my 9u cabinet. I have removed all the modules from the middle row and tried them individually and the problem still occurs.

The excessive noise from the filter happens if I connect the filter to ANY point on the middle row.  It does not happen on the top or bottom rows.  

I am concerned that it may be the power supply or would you still suggest that the filter is faulty.

Many thanks

Carter