How can I initialize a patch for jpv3? There's "default" patch for the previous version.
Or is there somewhere I can download one ?
Do you own the previous so you have the old default preset?
If so, then you can save it as a user preset, and then convert it using the VC5 preset converter you can download from here:
https://www.arturia.com/support/updates&manualsBut you can also create your own init preset.
A init preset is just a preset you use as a starting point to create sounds. Any preset can be such a init perset, if it works for you. Usually a init preset has very simple settings with no effects or modulation.
You can create different init presets or templates as init presets actually are.
This is related to your question:
http://forum.arturia.com/index.php?topic=88375.msg136250#new