Hi
If you did it as described in manual and used the "nosound"
method, you should still have the "old" sounds as before.
Anyway, what's really changed is described if you follow the
link at the bottom of the "update manual" page.
To downgrade, I think you have to find the 3.0c version of
the pbank files, and then follow what you can read in page
121 in Ketron SD1 manual before update only the OS again.
However, I'm not, I repeat, NOT any clever at the SD1 at all,
and to be sure about what to do, you can try contact Ketron
support by email or by use the contactfield at
www.ketron.it Or, if any luck, maybe AJ see this and take time to give some
advice? Also you could seek through the other posts here and
see what to find about the topic.
Myself I think I stay with 4.0c and the new sounds. I don't
really remember how the edited ones sounded like before, cause
I did update at once I got the SD1 to have the newest OS and
the new sounds, who I think are similiar as SD1 Plus now?
Happy Playing
GJ