Doepfer

The jacks work this way. This is a very basic description and you may  
know all of this already. Since these are plastic jacks there are two  
contacts that physically touch the 1/8 inch plug when inserted. The  
Ground (or Earth for our English brethren) touches the sleeve (closest  
to the outside of the module) and the signal touches the tip. The  
jacks used have 4 legs soldered to the PCB. one leg each go to the  
springy metal leaf that connects to the tip and sleeve. the other two  
legs opposite of them connect to two metal pieces the these springy  
metal parts rest against when no plug is inserted thusly making a  
"normalized" connection (the non plugged jack is considered in it's  
normal state - plugging in something makes it not normal - go figure).  
Typically there is no reason to use the normalization on the ground of  
the jack. This is mainly used in headphone type situations when you  
want to completely switch a isolated circuit between two destinations  
(switching off the speakers when inserting headphones for example). I  
doubt that it is used this way anywhere in the Doepfer system since  
the ground is shared in all modules but I may be wrong. In any case,  
when the plug is inserted the springy part of the connection is pushed  
away from the metal normalized contact and the connection is broken  
being replaced by the plug's signal. To make it work for banana plugs  
you have to 1) make the plastic hole larger to accommodate the banana  
plug  2)bend or cut out the ground connection so it doesn't touch any  
part of the banana (and not shorting out the signal by doing that). 3)  
Try not to bend the tip piece when drilling - you may have to do some  
slight disassembly and re-assembly. The metal pieces in the jack are  
removable and re-insertable if done with care. If done right the  
banana plug will push the contact away, breaking the normalization in  
the same manner as the 1/8 inch jack would. The main thing is to  
REMOVE THE GROUND CONTACTS from the equation. If left in they will  
short out the signal when the banana plug is inserted. This also means  
that the ground connection has to be made another way between the  
banana-modified Doepfer and any other unit patched to it.
I hope that helps some...
-James



On Jul 19, 2008, at 4:32 PM, williambbaggett wrote:

> Hi Group,  and thanks for your many  suggestions about how I might  
> use banana cords to
> interface with a Serge system.
>
> Well, I've ordered but not yet received a pretty larger Doepfer  
> system, and based on the
> advice received here,  am prepared to drill out the plastic in the  
> middle of the 3.5mm
> mini-plugs just a bit so as to to allow them to receive 4 mm banana  
> plugs. (instead of
> patch bays or adapter cables, etc.)
>
> I understand now that I have to disconnect ground from ever "banana  
> adapted" socket or
> else I would ground out the signal coming in on the banana.
>
> However,  I can't understand why trying to use banana jacks in  
> normaled sockets would
> not  create a similar problem.  I dunno, but need to know soon -  
> since I don't intend to
> touch a normaled socket until I do.
>
> THE ONE THING I CAN'T FIGURE OUT IS:
>
> James (or was it Korhan?) wrote:
>
>>> if carefully done the tip part of the jack could still be used and  
>>> make
>>> contact with the banana and EVEN THE NORMALIZING PRESERVED.
>
>
> I admit to being no expert and certainly capable of asking questions  
> without being able to
> understand the (correct) answer, but I don't really get it and I  
> certainly want to make sure
> before I stick a a banana pug in a drilled out/enalarged NORMALED  
> socket.
>
> Do I need to:
>
> (1) just leave the normaled mini-phone sockets ALONE and only drill  
> out the sockets that
> aren't?
>
> (2) somehow disable the normaling and waste a patch cord or 4  now  
> and then? (& If so,
> how?)
>
> (3) treat normaled sockets just like the rest
>
> It's this  3rd option I don't understand, and is why I write.
>
> I  looked at a schematic of a switched jack and it looked like  
> "normally" the normaled
> connection between 2 contacts is  broken by the insertion of  a mini- 
> plug (The insertion
> separates 2 contacts that would "normally" be connected)
>
> Here's the part that worries me – while the normalled connection is  
> broken, one contact is
> touching the tip of the mini-phone jack and the other contact is  
> isolated and touching the
> sleeve (or whatever you call it) of the mini-plug.
>
> So. since the banana plug has no sleeve, the two contacts would NOT  
> be isolated and the
> connection between the 2 contacts would NOT be broken when a banana  
> plug is inserted.
>
> Also, seems like the same banana plug would be connected to both  
> contacts and – So,
> what would happen to the signal carried by the banana cable? It  
> seems like this might
> result in stacking inputs (1. the normalled input that wasn't  
> disconnected with the plug
> was inserted and 2. the signal coming from the plug itself.)
>
> Well, the "question" turned out longer than I expected. Sorry, but  
> I'd appreciate any
> advice. I hope I'm wrong and can somehow use normalled inputs with  
> banana plugs, but I
> dunno... Whattaya think ?
>
>        Thank
>        Billy
>
> P.S. Please let me know if any of you have any  ideas or can foresee  
> any potential
> problems, etc. Thanks again!
>