Doepfer

Hi Heinz,

> i have a question regarding the A-185 module (bus access). what
> exactly must i do to get it into 'read only' mode? 
> according to the manual it depends on a jumper, but the module 
sports
> two jumpers and there are no detailed instructions as to how to
> proceed (i'm unfortunately completely unknowledgeable w.r.t. 
electronics).
> i want to mount the module in a frame that already HAS one A-185
> mounted in it (i want additional CV and gate outputs on that frame)
> and apparently this doesn't work when both are in read/write mode. 

The manual does seem a little confusing, but I think most of the 
information is there. Each section of the 185 (one for 'CV', the 
other for 'gate') consists of a 'buffer' (or 'refresh amplifier' in 
the manual) connected between the 'in' and 'out'. The jumpers control 
whether the internal bus bar is connected to the in or out. In the 
factory setting (with the jumper in the position of the thick line on 
the PCB), the system bus is connected to the output, as Fig 1 shows. 
Hence feed CV and gate signals from the 'master' to the inputs: this 
then goes to the bus bar to which the A-185 is connected, *and also* 
to the output sockets, so another A-185 on another bus bar can 
be 'daisy-chained', as Fig 2 shows.

If you swap the jumpers to the other position (for 'read mode'), the 
system bus is connected to the inputs of the buffers, and hence the 
buffered signals are avaliable at the outputs, this is Fig 3 (and 
note that the diagram is a little incomplete: the input now *is* the 
system bus, and so the statement immediately above it isn't correct!).

If you are solely using Doepfer modules, there should be no need for 
the read mode, as the manual says, as if you think you need to read 
what is on the bus, you should be able to take it from what put in 
there (either an A-185 or A-190, as Fig 2 shows). However if you have 
a different module writing signals to the bus, and that is why you 
need to read it using an A-185, then Doepfer have taken the view that 
you know what you are doing, hence the "won't go into any more detail 
here" statement (which is probably not unreasonable in my view!).

And I hope this doesn't make things more confusing!

Tim