Doepfer

Speaking of connectors in the back, if I were to install a DIN socket 
in back of an A100 frame and wire the midi signal internally to the 
A190 and A191, would simple wire work OK? Shielded two-conductor? Thin 
coax?

Joe

Hi Joe,

> Speaking of connectors in the back, if I were to install a DIN 
socket 
> in back of an A100 frame and wire the midi signal internally to the 
> A190 and A191, would simple wire work OK? Shielded two-conductor? 
Thin 
> coax?

The simple introductory book I have on MIDI says that screened twin 
core cable of audio quality is fine. BUT, MIDI is not 
straightforward. It works off a 'current loop', with opto-isolators 
used to ensure that interconnected bits of kit are electrically 
isolated from one another. The book strongly advises against trying 
to drive two inputs from a single output (you wouldn't be able to 
guarantee that either input would work properly) - this means that 
you would still have to run your A-191 from the 'thru' of the A-190 
(although conceivably you could connect them internally). Also the 
point of using screened cable is to prevent interference 
from 'escaping' from the lead, and not from noise penetrating it - 
the screen on a lead is attached to both pin 2's at either end, but 
the pin 2 on any socket is *not* connected to the chassis, in order 
to maintain the isolation of all bits of kit.

I'm not sure how helpful the above is - you were obviously expecting  
to connect things internally, only it might be less simple than you 
had imagined (?).

Tim

Hi Timothy thanks for the information.

I have the A190's midi thru jack wired internally to the 
A191's midi in jack with two short lengths of wire. That's been 
working fine for a couple of years.

So now I'm thinking that if I connect a cable from a rear-panel DIN 
socket to the terminals on the A190's midi in jack, whatever opti-iso 
stuff is going on should be preserved. Do you think?

Joe

--- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" <timothy@t...> 
wrote:
> Hi Joe,
> 
> > Speaking of connectors in the back, if I were to install a DIN 
> socket 
> > in back of an A100 frame and wire the midi signal internally to 
the 

> > A190 and A191, would simple wire work OK? Shielded two-conductor? 
> Thin 
> > coax?
> 
> The simple introductory book I have on MIDI says that screened twin 
> core cable of audio quality is fine. BUT, MIDI is not 
> straightforward. It works off a 'current loop', with opto-isolators 
> used to ensure that interconnected bits of kit are electrically 
> isolated from one another. The book strongly advises against trying 
> to drive two inputs from a single output (you wouldn't be able to 
> guarantee that either input would work properly) - this means that 
> you would still have to run your A-191 from the 'thru' of the A-190 
> (although conceivably you could connect them internally). Also the 
> point of using screened cable is to prevent interference 
> from 'escaping' from the lead, and not from noise penetrating it - 
> the screen on a lead is attached to both pin 2's at either end, but 
> the pin 2 on any socket is *not* connected to the chassis, in order 
> to maintain the isolation of all bits of kit.
> 
> I'm not sure how helpful the above is - you were obviously expecting 
 
> to connect things internally, only it might be less simple than you 
> had imagined (?).
> 
> Tim

> I have the A190's midi thru jack wired internally to the 
> A191's midi in jack with two short lengths of wire. That's been 
> working fine for a couple of years.
> 
> So now I'm thinking that if I connect a cable from a rear-panel DIN 
> socket to the terminals on the A190's midi in jack, whatever opti-
iso 
> stuff is going on should be preserved. Do you think?

Yep. As long as you connect pin-for-pin (pins 4 and 5), like you have 
obviously had to for the 190-191 connection, you should be OK.

Tim

Hi Tim

> ...The book strongly advises against trying
> to drive two inputs from a single output (you wouldn't be able to
> guarantee that either input would work properly) 
I was using paralleled MIDI-Outs for several MIDI-Ins for years. I had only
one combination of a certain Devices MIDI-In with the MIDI-Out of my SBX-80
did not work. I measured the resistor, that gives the current feed for the
loop, in the SBX and found, that it was out of the specification. After
replacing with the resistor with the correct value, also this worke again
fine.

Florian