(This has got to be the strangest cross-post I've
ever done.)
You've got that right :P
I do sincerely apologize for
cross-posting, but I am rather younger than either of these
technologies (vintage: 1984) and this seems like a monumental
challenge.
Well, several projects can be thought off in this scenario, but
if you want to keep it mildly useful, try to do something with
audio tubes connected to an '11 (OK, here's a spoiler: "you'll
make a PDP11-driven music player using a tube-based audio
backend"), or such. You could go into analog computing as
well, but that can be kinda hairy.
This more or less only requires building a usable D/A converter
on the '11, which then interfaces to the tubes. I'd use a DMA-
based 16-bit DA controller.
Cheers,
Fred (smiling @ his nano-11 system running Ultrix, all the size of
a matchbox..)