Doepfer

--- In Doepfer_a100@yahoogroups.com, Florian Anwander 
<Florian.Anwander@c...> wrote:
> Hello Dieter
> 
> > If I'm not mistaken 8 S&H's and switches are required for a 4 
stage analog
> > shift register (similar to the BBDs) as you need a n additional 
slave S&H
> > for each stage.
> I do not think, you need an additional slave S&H, if you decouple 
not 
> only the s&h with the input selector, but also the trigger, which 
clocks 
> the s&h.
> 
> > This is required to have the analogue value available to
> > forward it to the following stage as the preceeding S&H already is
> > "reloaded" from the stage before. 
> I would avoid to forward the content of one stage to the other 
(causes 
> voltage loss and adds noise). Instead of, I suggest to use a 
clocked 
> 1to8 switch, to switch the output of one s&h-stage to the eight 
outputs.
> 
> Let me try ASCII sketch (you need courier as font for this):
> 
> 
> |--common part--|--for each stage-------|
> 
>            +-...        +------out-bus-5
>            |            |
>            +-...        +------out-bus-6
>            |            |
>            +-...        +------out-bus-7
>            |            |
>            +-...        +------out-bus-8
> CV in o---|            |
>            +-----s&h_5--+------out-bus-1
>            |      |     |
>            +-...  |     +------out-bus-2
>            |      |     |
>            +-...  |     +------out-bus-3
>            |      |     |
>            +-...  |     +------out-bus-4
>         CD4051    |   CD4051
>                   |
>            +-...  |
>            |      |
>            +-...  |
>            |      |
>            +-...  |
>            |      |
>            +-...  |
>            |      |
> Clock in--|      |
>            +------+
>            |
>            +-...to s&h_6
>            |
>            +-...to s&h_7
>            |
>            +-...to s&h_8
>         CD4051
> 
> The assignment of the outputs at the right CD4051 has to change 
round 
> robbing.
> 
> Not shown is a adress counter, clocked by the clock, which feeds 
all 
> CD4051 (of course we should not use 4051 because of the know 
pitfalls).
> The outbut buses should not require adders, becaus always only one
> 
> 
> 
> Florian


maybe it is interesting to look at the anlog shift register
of ken stone too, he offers pcb's for such a module.
he speaks of a four-stage s&h for a three-stage shift register.

best wishes

ingo