Bi-N-Tic Damping pot wiring is backwards on the schematic
2006-05-27 by Richard Brewster
If you have output level problems with the Bi-N-Tic this may be your
problem. The wiper and top of the Damping pot are reversed on the
Bi-N-Tic filter schematic. I thought it looked odd, but I wired it as
shown at first. This is the symptom: the damping pot has a working
range only near zero, and if turned to zero the output of the filter
just about disappears. If you look closely, you'll notice that the pot
wiper (as shown on schematic) is connected to IC2 pin 6, the output of
an op amp. When Damping is turned all the way down, as originally
wired, this op amp output is shorted to ground. (No damage results
though.) The schematic also does not show the 10K resistor in series
with IC1 pin 3. The fix is easy: just swap the center and top wires on
the pot. Now the output of IC2 is going to the top of the pot, and the
wiper is connected to the 10K resistor. This change makes a HUGE
difference to the sound. It works correctly now.
Richard Brewster
http://www.pugix.com
problem. The wiper and top of the Damping pot are reversed on the
Bi-N-Tic filter schematic. I thought it looked odd, but I wired it as
shown at first. This is the symptom: the damping pot has a working
range only near zero, and if turned to zero the output of the filter
just about disappears. If you look closely, you'll notice that the pot
wiper (as shown on schematic) is connected to IC2 pin 6, the output of
an op amp. When Damping is turned all the way down, as originally
wired, this op amp output is shorted to ground. (No damage results
though.) The schematic also does not show the 10K resistor in series
with IC1 pin 3. The fix is easy: just swap the center and top wires on
the pot. Now the output of IC2 is going to the top of the pot, and the
wiper is connected to the 10K resistor. This change makes a HUGE
difference to the sound. It works correctly now.
Richard Brewster
http://www.pugix.com