Hi

> I either find a Boss Phase(!) Shifter PS-10 or Pitch shifters PS-3 /
> PS-5 in Google. Never heard from a RPS 10

Whoops, must have overlooked a pile of links in Google....

>> pitch. The input seems to be normalled to the pitch pot since it
>> does't work as soon as the 'kbd controll' jack is in use. However, the
>> result is: neither the pitch pot works nor can I controll the device
>> with any CV from my A100.

Try to find out what voltage is sent by the pitch pot. You might try to
insert a cable not completely, so the tip of the jack has contact to the
connector inside the socket but the normalization switch is not touched
yet.
The easy way would be to open it and measure with a voltmeter at the
center pin of the pot against 0 Volt.

Florian