I've breadboarded the circuit and followed the schematic that you posted.
I'm getting output but things are rather noisy coming from the 324
also the schematic at freeinfo looks different.http://www.freeinfosociety.com/electronics/schemview.php?id=135
my question is specifically about where the 4558's output is going
in the scheme you posted, from the junction of the two 33k resistors the lead appears to go to a positive (top) and negative (bottom) 324 input
from the end of the two 33k Rs, the lead seems to go straight to positive inputs of the first section of the 324
the freinfo schem shows the juction lead going to two negative ins
this would mean that the last section of the 324 is set up as a differential amp
so I figure that the freinfo schem is correct
I ran out of time to redo the leads (even though I knew it would only take a minute). I had already made the desicion to get some sleep.
I'll try it the other way when I get home from work.
Just a heads-up in case anyone else is trying this