DIY tape echo -- possible?

[scott]

I've been working on setting my reel to reel tape
recorder to work as an echo. This ofcourse involves
getting the unit to play and record at the time,
the echo delay based on either the physical space between
the two heads and the playback speed. OK.

My problem... My reel to reel only has two heads,
erase & play/record. I've sucessfully hacked on an old
walkman playback head, but it only doubles the function
of the other head (either both playback or both record.)
I've tried to alter the electronics so that it would do
both simultaneously, but with no luck.

What I want to know is, how hard would it be to build a
circuit that'd translate audio to/from the three tape heads,
so that I can detach all three heads from the current circuit
and run the new output straight to a jack. I'm really looking
for the simplest circuit that'll do this. 

Any help is appreciated.

thanks,
scott

64k at geocities.com