The 1967 ARRL handbook has one on page 148. It uses a 12AU7 and two 88 mH
toroids. Might that be what you were thinking of?
Bill N9BT

"Ron" wrote in message
...
Hi, I'm building a small valve communication receiver in an
effort to recapture some of the fun of my youth ))
And I am trying to find a circuit of a simple valve CW Audio filter
Years ago I built one from a circuit that was in the ARRL handbook
about 60's vintage, that was superb, anyone got an old Handbook
of that vintage that could have a look and possibly scan the
info, or possibly have a good one of their own using standard
valve componants!! long shot I know )
Thanks from Ron G3YUH