I fully agree. As the A-100LC3 also uses an external power supply it's GND
is not connected to mains earth/GND and has the mentioned "floating GND" (in
contrast to all other A-100 cases).

Best wishes
Dieter Doepfer

> Definitely get that case properly earthed first. Even if its not
> causing this issue, its not safe for you or your equipment. There
> should be a both crimped and soldered lug on the metal case, held
> in good contact with a screw and washers which connects to earth.
> This probably can be done by connecting the PSU ground to the
> case, but its worth checking that the case actually is
> electrically connected to the ground pin on your wall socket.
> Some PSUs with external bricks have a floating ground
>
>
> On 12 Jun 2018, at 14:20, Diego Ragnini diegora@...
> 1 <Doepfer_a100@yahoogroups..com> wrote:
>
>
>
> Thanks, the cables are all recent doepfer
> Not sure to know how to do this experiment though I will try.
> Which GND do you refer to
> Just the one of the audio 2 (the source which feeds the A138s) or
> the multed audio 1 as well
> Audio 2 is from a DPO mounted on a A-100P9 PSU3
> Audio 1 is from a Bastl Instruments SoftPop, which in the
> meanwhile went back to the dealer to be replaced for another kind
> of issue. I had noticed some electricity at fingers while
> touching the side panels of its case. It probably is not properly
> grounded, though it shows some sockets for grounding...
>
> Best wishes,
> Diego
>
> > Il giorno 12 giu 2018, alle ore 14:54, yahoo@...
> 1 < Doepfer_a100@yahoogroups.com > ha scritto:
> >
> > As external audio signals are involved it maybe a grounding
> problem. Make
> > sure that the cables that are used to connect the modules to
> the external
> > signals carry GND (there are patch cables available without
> GND, as long as
> > one patches within the case no problems occur, but with
> external signals the
> > GND is missing). And I don't know if all WMD sockets are
> grounded. In some
> > modules (yes, also in some older A-100 modules :-) the GND of
> some sockets
> > is not connected as it does not matter if all modules are
> connected to the
> > same GND.
> > You may try also the following: connect the GND of the A-100LC3
> temporarily
> > to the GND of the signal source unit (at the A-100LC3 there should be an
> > unused GND terminal on the bus board). If then the problem
> disappears it's a
> > grounding issue.
> > It's just an idea. Not sure if this is the reason.
> >
> > Best wishes
> > Dieter Doepfer
> >
> >
> >> -----Ursprüngliche Nachricht-----
> >> Von: Doepfer_a100@yahoogroups.com
> 1
> >> Gesendet: Dienstag, 12. Juni 2018 14:06
> >> An: Doepfer_a100@yahoogroups.com
> >> Betreff: Re: 1 Interferences from A-138s into LC6
> >>
> >>
> >>
> >>
> >> Hi thanks everybody for replying
> >> The situation was vague indeed, sorry, though the patch is very basic
> >> The case is just 1 row (LC3)
> >> As you can see by the colours on the following screenshot, the
> >> multed audio 1 signal (red cable) is slightly affected by the
> >> audio 2 signal (blue cable), as we turn CW the A-138s channel
> volume knob.
> >>
> >>
> >> Nothing else is patched/ engaged.
> >>
> >>
> >> I unfortunately have no means nor expertise for measuring anything...
> >> ASAP I will first try installing the multiple on another case.
> >>
> >>
> >> Best, Diego
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> Il giorno 12 giu 2018, alle ore 10:25, John Hollis
> >> john@... 1 < Doepfer_a100@yahoogroups.com >
> >> ha scritto:
> >>
> >>
> >> Hi Diego,
> >>
> >> It does sound like there might be a short between the adjacent
> >> modules. Can you check for that
> >>
> >> Thanks
> >> John
> >>
> >>> On 12 Jun 2018, at 08:57, yahoo@... 1
> >> < Doepfer_a100@yahoogroups.com > wrote:
> >>>
> >>> Hello,
> >>>
> >>> the A-138s is a very simple module (just a standard mixer circuit with
> >>> operational amplifiers) and I have no idea how the signal could
> >> crosstalk to
> >>> any other module.
> >>>
> >>> Best wishes
> >>> Dieter Doepfer
> >>>
> >>>> -----Ursprungliche Nachricht-----
> >>>> Von: Doepfer_a100@yahoogroups.com
> > [mailto: Doepfer_a100@yahoogroups.com ]
> >>> Gesendet: Montag, 11. Juni 2018 15:09
> >>> An: Doepfer_a100@yahoogroups.com
> >>> Betreff: 1 Interferences from A-138s into LC6
> >>>
> >>>
> >>> Hello, I have a WMD buffered multiple which suffers from A-138s
> >>> mixer interferences, both powered by an LC6 Doepfer case. Is the
> >>> WMD faulty or its cable A-138s output can be heard on the WMD,
> >>> unless knob's fully CCW. I also see that the multed signal is
> >>> louder that the original one. Any hint is welcome.
> >>>
> >>> Best regards,
> >>> Diego
> >>
> >>
> >>
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
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